Language：Others   Publishing type：Research paper (scientific journal)   Publisher：IEEE Sensors Letters  

Visualization of gaseous chemical substances, such as odors, is very challenging, and few studies are being conducted to address this issue. These odor visualization technologies are expected to be more beneficial for various applications, such as detecting hazardous or human relating gas source localization. Currently, semiconductor gas sensors are commonly used for gas measurements; however, these sensors have disadvantages, such as slow response time and inability to detect multiple types of gases. Furthermore, it is difficult to understand how gases are distributed in space. Thus, we have developed a gas sensor utilizing localized surface plasmon resonance (LSPR). LSPR gas sensors enable real-time, high-speed response and recovery, and by analyzing wavelength information using a hyperspectral camera, gas imaging and identification become possible. In this letter, we conducted experiments on visualizing the spatiotemporal distribution of multiple gases and identifying gas space through the analysis of spectral information using a 2-D LSPR gas sensor and a hyperspectral camera. As a result, we successfully visualized and identified the distribution of each gas in a situation where multiple gases were present by performing principal component analysis analysis on the spectral data obtained from hyperspectral images.

DOI： 10.1109/LSENS.2023.3301847

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：npj Flexible Electronics  

A method was used to fabricate a fully inkjet-printed gas sensor matrix on photographic paper. An electrode matrix comprising 36 interdigital electrodes in a high-density layout that is easy to integrate has been fabricated using a combination of insulating ink and commercial silver ink. Molecular-imprinted polymer (MIP) inks were then made using a simple solution mixing method, and these inks were printed together with carbon black ink on the electrode matrix to complete production of the sensor. Finally, experimental dynamic sensing of volatile organic compounds verifies that for detection of gases corresponding to the MIP template molecules, the MIP layer offers improvements in both sensitivity and selectivity when compared with non-imprinted polymer layers. The matrix can produce a response of more than 20% to 3 ppm propenoic acid gas through adjustment of the printing times for the carbon black layer and the MIP layer.

DOI： 10.1038/s41528-022-00168-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACS Sensors  

The fabrication of chemiresistive sensors by inkjet printing is recognized as a breakthrough in gas-sensing applications. One challenge of this technology, however, is how to enhance the cross-selectivity of the sensor array. Herein, we present a ketjen black (KB) ink and molecularly imprinted sol-gel (MISG) inks to support the fabrication of a fully inkjet-printed chemiresistive sensor array, enabling the highly accurate recognition of volatile organic acids (VOAs) on the molecular level. The MISG/KB sensor array was prepared on a glossy photographic paper with a three-layer structure: a circuit layer by a commercial silver ink, a conductive layer by a KB ink, and an active selective layer by MISG inks imprinted by different templates. Hexanoic acid (HA), heptanoic acid, and octanoic acid were used as templates to prepare the MISGs and as targets to evaluate the detection and discrimination performance of the sensor array. Three resultant MISG/KB sensors exhibited high sensitivity and selectivity to VOA vapors. The limit of detection and imprinting factor were 0.018 ppm and 7.82, respectively, for HA-MISG/KB sensors to the corresponding target. With linear discriminant analysis of the gas responses, the MISG/KB sensor array can realize high discrimination to VOAs in single and binary mixtures. Furthermore, the proposed sensor array showed strong sensor robustness with excellent consistency, durability, bending, and humidity resistance. This work developed a fully inkjet-printed chemiresistive sensor array, enabling the realization of high cross-selectivity detection, achieving low-cost, scalable, and highly reproducible sensor fabrication, moving it closer to reliable, commercial, and wearable multi-analyte human body odor analysis potential.

DOI： 10.1021/acssensors.2c00093

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：IEEE Sensors Journal  

We synthesized gold (Au) nano-urchins (AuNUs) and deposited these AuNUs on indium tin oxide (ITO) glass. We compared the influence of the resistance of ITO glass and the deposition density of NUs on refractive index sensitivity (RIS) of these ITO substrates, and found that ITO glass with resistance of 8-12/sq and substrates with many AuNU dimers gave the highest RIS which was as high as 455 nm/RIU (refractive index unit), which is the highest on substrate as we known. Compared with AuNUs deposited on quartz glass, the extinction peak intensity and RIS were enhanced on ITO glass. The RIS enhancement is mainly attributed to the considerably enhanced electric field at the tips of AuNUs, electrical hot spots generated by AuNU aggregates (such as dimers), and the repulsive forces decrease in each AuNU by the ITO layer. It is thought that further shape, distribution, and size change of AuNUs and dimers on ITO glass will greatly affect the RIS and spectral characteristics. AuNU substrate is then proposed for heparin detection through Au etching. The results showed that heparin detection was realized in a linear range of 0.05 to 5μ g/mL with a detection limit of 8 ng/mL, which has potential to be applied in the practical environment.

DOI： 10.1109/JSEN.2022.3155792

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Sensors and Actuators B: Chemical  

A meta-learning algorithm, conventionally used for visual recognition, was applied to the recognition and classification of aroma oils. A printable chemiresistive sensor array was fabricated, based on composites of carbon black with various active materials. Standard aromatherapy kits with 30 types of essential oils were used as targets in an odor sensing experiment. Benefiting from the pattern recognition ability of the fabricated sensor array, a high-quality dataset was obtained with 30 aroma oil classes, in which each class had nine replicate samples. A deep metric learning model, based on a Siamese neural network and a multilayer perceptron, was used to perform the N-way k-shot meta-learning. A test accuracy of over 98.7% was obtained for 31-way 9-shot learning, on discriminating whether the input pair samples were taken from similar or dissimilar classes. The model was effective in extracting meta-features of the aroma oils; this was proved by the improved clustering effect of samples in the spaces of principal components analysis and t-distributed stochastic neighbor embedding. The 30 aroma oils were divided into two datasets according to 6-fold cross-validation: 25 aroma oil classes (plus one blank class) as seen classes for constructing 26-way 9-shot learning models and the remaining five aroma oils as unseen classes for prediction. Average accuracies of 93.5% and 93.9% were achieved for recognition of the unseen aroma oils from the seen classes and classification of the unseen aroma oils themselves, respectively, demonstrating the effectiveness of the developed sensor and model for odor recognition and classification.

DOI： 10.1016/j.snb.2021.130960

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Journal of Food Science and Technology  

The study aims identification of discriminating chemical constituents in the banana odor grown in Philippines and Ecuador using GC–MS characterization. Ester is recognized as a major chemical class in selected banana odor. Odors discriminating compounds like, 2-hexenal, ethyl acetate, and hexanoic acid, ethyl ester, etc. have been identified. Besides, other odors generating chemical compounds (alcohols, esters, aldehydes, and ketones) have been recognized. Furthermore, principal component analysis (PCA) and hierarchical cluster analysis were implemented to differentiate banana odors. PCA achieved 100% discrimination of selected bananas odors using the peak area information about recognizing chemical compounds. Odor identity and discrimination of selected bananas have been achieved successfully.

DOI： 10.1007/s13197-021-05298-9

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Low-invasive soft robotic techniques can potentially be used for developing next-generation body–machine interfaces. Most soft robots require complicated fabrication processes involving 3D printing and bonding/assembling. In this letter, we describe a monolithic soft microrobot fabrication process for the mass production of soft film robots with a complex structure by simple 2D processing of a robotic actuator film. The 45 µg/mm2 lightweight film robot can be driven at a voltage of CMOS compatible 5 V with 0.15 mm−1 large curvature changes; it can generate a force 5.7 times greater than its self-weight. In a durability test, actuation could be carried out over 8000 times without degradation. To further demonstrate this technique, three types of film robots with multiple degrees of freedom and a moving illuminator robot were fabricated. This technique can easily integrate various electrical circuits developed in the past to robotic systems and can be used for developing advanced wearable sensing devices; it can be called “Kinetic electronics”.

DOI： 10.1038/s41598-021-99500-9

Language：Others   Publishing type：Research paper (other academic)  

A two-dimensional gas sensor with distributed response characteristics was fabricated by depositing silver in a pattern on an AuNPs substrate, and a method to estimate multiple mixed gas concentrations using the fabricated substrate was proposed. We also proposed a method to estimate multiple gas concentrations using the fabricated substrates with linear analysis. The gas concentrations were calculated using the different response characteristics distributed on the fabricated Au/AgNPs LSPR (Localized Surface Plasmon Resonance) 2D gas sensor elements having sub-pixel patterns adjusted by image analysis. Linear regression analysis was employed to successfully estimate the gas concentration. This sensor device is expected to be applied to gas image sensors that can visualize odor and gas distribution.

DOI： 10.1109/SENSORS47087.2021.9639593

Language：Others   Publishing type：Research paper (other academic)  

Volatile organic acids are important compounds related to specific diseases from human body odor. In this research, paper-based chemiresistive gas sensor was proposed based on inkjet printing technology using desktop inkjet printer. We formulated an alcoholic-based ketjen black ink to construct conductive layer. In addition, molecularly imprinted sol-gels ink was synthesized to realize specific selectivity. To obtain best sensor performance, the main two parameters, template concentration and crosslinker/monomer ratio, were optimized. This work demonstrated that the paper-based MISG gas sensor have a great potential for rapid, sensitive, and selective gas detection.

DOI： 10.1109/SENSORS47087.2021.9639251

Language：English   Publishing type：Research paper (scientific journal)  

The Surface-Enhanced Raman Scattering (SERS) technique is utilized to fabricate sensors for gas detection due to its rapid detection speed and high sensitivity. However, gases with similar molecular structures are difficult to directly discriminate using SERS gas sensors because there are characteristic peak overlaps in the Raman spectra. Here, we proposed a multiple SERS gas sensor matrix via a spin-coating functional polymer to enhance the gas recognition capability. Poly (acrylic acid) (PAA), Poly (methyl methacrylate) (PMMA) and Polydimethylsiloxane (PDMS) were employed to fabricate the polymer film. The high design flexibility of the two-layer film was realized by the layer-by-layer method with 2 one-layer films. The SERS gas sensor coated by different polymer films showed a distinct affinity to target gases. The principle component analysis (PCA) algorithm was used for the further clustering of gas molecules. Three target gases, phenethyl alcohol, acetophenone and anethole, were perfectly discriminated, as the characteristic variables in the response matrix constructed by the combination of gas responses obtained 3 one-layer and 3 two-layer film-coated sensors. This research provides a new SERS sensing approach for recognizing gases with similar molecular structures.

DOI： 10.3390/s21165546

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Herein, we report a novel full printing process for fabricating chemiresistor gas sensor matrixes on photographic paper with an inkjet printer. Sensor matrices, which can increase a number of sensors significantly compared to a serial sensor array, were printed on one piece of A4 photographic paper. Each sensor matrix contains 36 interdigital electrodes in an area of less than 11 mm2, which greatly improves the density of the sensor. The basic architecture of the sensor matrix is electrodes that row and column intersecting. In order to insulate the row and column electrodes from meeting each other, an insulating layer needs to be fabricated at the point of intersection between the row and column electrodes. The insulation layer was produced by adjusting the number of printing passes and shape of the printing pattern of color pigment ink. Carbon black (CB) was used to form a chemosensitive composite by changing its resistivity with a specific polymer for the preparation of sensing material. In order to make the sensing material can be printed, it is necessary to disperse CB first. CB was dispersed in aqueous solution with sodium dodecyl sulfate added as a surfactant to lower the surface tension, which enabled printing of CB using an inkjet printer. Some polymers have certain adsorption characteristics for gases. According to the different gas properties, the adsorption characteristics are also different. By adding polyethylene glycol polymer to the CB layer, the response to four gases with different properties is improved. Compared with the drop coating, the full-printing sensors not only reduces the production time significantly, but also improves the gas response magnitude to ethanol by about three times. The results demonstrate that the developed sensor can be used as a low cost, disposable, and easily printable chemical sensor.

DOI： 10.1088/2058-8585/abec19

Language：Others   Publishing type：Research paper (scientific journal)  

A molecularly imprinted sol-gel (MISG)/Au@Ag core-shell NU sensor is proposed for organic vapor detection in an optical fiber-based reflection mode. The compact structure design of the system in the reflection model is promising for practical use as a portable and rapid responsivity sensing probe. Volatile organic acids (OAs) are analogs to biogenetic volatile organic vapors related to specific human diseases. Here, Au@Ag core-shell nano-urchins exhibiting branched tips were synthesized and deposited on indium tin oxide (ITO) glass in small dimer and trimmer clusters to generate an enhanced electric field. A MISG solution was then spin-coated on the substrate to fabricate MISG-LSPR sensors, and three types of MISGs were developed for the detection of hexanoic acid, heptanoic acid and octanoic acid. The normalized spectral response indicated selectivity of the MISG-LSPR sensors for the corresponding template OAs. With Native Bayes and linear discriminant analysis of the sensor responses, where the latter were detected by the proposed system, single- and mixed-OA vapors could be classified into separate clusters. This signified that the proposed MISG-LSPR sensor can be applied toward pattern recognition of single vapors or multiple vapor mixtures.

DOI： 10.1016/j.bios.2020.112639

Language：Others   Publishing type：Research paper (scientific journal)  

<p>The response of MISG@Au nano-urchin sensors indicated that selectivities of the MISG@Au nano-urchin sensors to the corresponding plant biomarker VOCs were generated <italic>via</italic> the branched tips of Au nano-urchins and their electric field coupling effects.</p>

DOI： 10.1039/c9tc05522c

Language：Others   Publishing type：Research paper (other academic)  

LSPR (Localized Surface Plasmon Resonance) based 2D (Two-dimensional) gas sensor system which can measure and identify multi-gases with high spatial resolution have been developed. The gas sensor detects optical changes promoted by the gas on the LSPR substrate with hyperspectral camera. Basically, LSPR gas sensor does not have a molecular selectivity, then the identification of gas species is difficult. To overcome the disadvantage, LSPR substrates based on Au/Ag core-shell structure with spectral gas-discriminating ability through optical interaction were fabricated by spin coating fluorescent dyes. Using the LSPR coupled with fluorescent dyes, this sensor provides rich spectral information about the detecting molecules and can discriminates gas species.

DOI： 10.1109/SENSORS47125.2020.9278828

Language：Others   Publishing type：Research paper (other academic)  

Geosmin (GSM) with an earthy odor resembling is often accompanied by 2-methylisoborneol (MIB), which caused the earthy and musty taste of drinking water. To detect trace GSM solution, we designed gas sensor by Surface-enhanced Raman Scattering (SERS) technology which has the capacity of single molecule detection. With our ultra-high sensitivity detection system, response range from 10 ppt to 10 ppb geosmin in ultrapure water was confirmed. Additionally, 100 ppt geosmin in tap water was detectable.

DOI： 10.1109/SENSORS47125.2020.9278909

Language：Others   Publishing type：Research paper (other academic)  

The Localized Surface Plasmon Resonance (LSPR) gas sensor is a promising for mounting on the robot due to an advantage of high-speed response speed and low power consumption. In addition, it is possible to change the characteristic by coating fluorescent dye on the LSPR surface. In this research, we have developed a robot equipped with multi LSPR gas sensor module for the purpose of the identification of gas species.

DOI： 10.1109/SENSORS47125.2020.9278605

Language：Others   Publishing type：Research paper (scientific journal)  

Generally, people distinguish the type of meat by looking at the color, texture, and even aroma of meat. These three methods have less effective approaches to distinguish the types of meat from meat cuts. Some researchers analyze the differences in the aroma of meats by using laboratory equipment, which is gas chromatography–mass spectrometry (GC–MS). This tool is mostly accurate, but it requires some time to determine the meat types completely. Moreover, the analysis process using GC–MS is also complicated. Nowadays, the electronic nose (e-nose) is a promising technology because it has a faster process of identifying various food types with reasonable production costs. Hence, the development of an e-nose for distinguishing volatile compounds from some meat types is appealing. Not only to determine the type of meat, but this study can also differentiate the part of the body from the meat, which has never been done by previous researchers. GC–MS was used as ground truth for the e-nose system, which helped the results to meet the standards. To achieve the objective in differentiating two meat cuts from three types of meat, this study uses statistical parameters for extraction feature, PCA for reducing the dimension, and deep learning. Furthermore, to get more improvements from the previous researches, this study aims to optimize the parameters of deep learning. The result of the proposed method was compared to several machine learning algorithms that were used in previous studies, i.e., k-nearest neighbor (k−NN), support vector machine (SVM), Multi-Layer Perceptron (MLP), and basic deep learning. The experimental results showed that e-nose could detect meat cuts for 120 s, and the proposed method provides a significant improvement.

DOI： 10.1016/j.sbsr.2020.100371

Language：Others   Publishing type：Research paper (other academic)  

LSPR (Localized Surface Plasmon Resonance) based 2D (2 Dimensional) gas imaging sensor system which can capture spatial distribution of each constituent of mixed gas have been developed. The gas image sensor detects the gas promoted optical changes occurred on the LSPR substrate by CCD camera. Basically, LSPR gas sensor does not have a molecular selectivity, then the identification of gas species is difficult. To overcome the disadvantage, pixelated LSPR substrate based on Au/Ag core-shell structure which has different gas response properties is fabricated by photo-induced metal growth by mask-less exposure system using a commercial video projector.

DOI： 10.1109/SENSORS43011.2019.8956635

Language：Others   Publishing type：Research paper (other academic)  

Various odor robots have been developed for finding gas sources. However, the response speed of sensors is now a major limit for the promotion of odor robot using chemical substances information. In this research, we have developed a robot equipped with two LSPR (Localized Surface Plasmon Resonance) gas sensor module that can quickly respond to gas molecules at a high speed of above 25 Hz and set a specific algorithm for tracking the invisible odor line on the ground.

DOI： 10.1109/SENSORS43011.2019.8956599

Language：Others   Publishing type：Research paper (other academic)  

This paper introduces a new method to fabricate a large - scale sensor array. By printing electrodes on photographic paper and making insulating layers, 6×6 arrays of sensors were obtained. Different gas selective can be printed in different units to detect different gases. Thus, production of multiple sensors in a small area with low cost was realized. On a piece of A4 photo paper, 30 sensor matrices can be printed at the same time. Each sensor array has 36 sensing units, thus theoretically identifying up to 36 gases. The sensor is suitable to be used in wearable devices to identify human skin gases due to its flexible substrate, low production cost and simple manufacturing process. In this experiment, molecular imprinted polymer (MIP) solution [1], carbon black (C.B.) conductive solution and insulating solution are prepared as ink, which can be used for ink-jet printer printing. This makes the method of developing the sensor more flexible. Compared with the sensor developed by micropipette to drop the MIP solution and C.B. conductive solution, the sensor developed by a printer has better uniformity.

DOI： 10.1109/SENSORS43011.2019.8956795

Language：Others   Publishing type：Research paper (other academic)  

Mixture of gas molecules must be accurately detected for gas sensor. However, there are certain difficulties in identifying the type of gas and detecting its concentration by chemical sensors. SERS (Surface Enhanced Raman Scattering) is a promising method for high sensitive gas detection because of its ability of molecule discrimination. However, it is difficult for SERS sensor to identify gases with the similar structure. In this research, we have developed a more selective SERS sensor with molecular filter layers. Molecular filter property is studied by coating a filter polymer film on the SERS substrate. The characteristics of the sensor with two membrane structures were also studied and different filtering properties were obtained.

DOI： 10.1109/SENSORS43011.2019.8956884

Language：English   Publishing type：Research paper (scientific journal)  

We investigated electron transfer during the time-dependent binding processes between thiolate molecules and Au nano-islands by observing tunneling current with an interdigitated microelectrode supporting the sputtered Au nano-islands (IME@AuNI). The time-dependent optical and electrical signal variation during the binding process was examined for five kinds of thiolates. As the immersion time was prolonged, the optical absorbance increased, whereas the current passing through the IME@AuNI decreased. Importantly, the spectral and current characteristics depended on the thiolate structure, because of the formation of capping layer in accordance with thiolate structure. These results are mainly attributed to synergistic effects of electron transfer from Au nano-islands to thiolate molecules and bridging effects of thiolate molecules among Au nano-islands.

DOI： 10.1016/j.apsusc.2018.12.138

Language：Others  

Our living environment is surrounded by a variety of odors. The visualized detection of odorant molecules may explore many new applications that cannot be realized by conventional sensors. This chapter introduces some novel sensing technologies that can be used to visualize both the odor space and odor quality. Fluorescence imaging sensors are developed to record the shape of odor sources and the spatiotemporal distribution of odor flows. Multispectral imaging-based odor visualization shows power in the structure-related discrimination of different odorant molecules. Localized surface plasmon resonance (LSPR) sensors based on metal nanoparticles show advantages in high-speed response and recovery in gas or vapor sensing. A sensor robot based on the LSPR sensors is developed to visualize the odor information from on-ground odor sources. In addition, data analysis based on physicochemical parameters of odorant molecules is carried out to demonstrate the difference of odor quality by using network-graph techniques.

DOI： 10.1016/B978-0-12-815409-0.00018-8

Language：English   Publishing type：Research paper (scientific journal)  

Detection of plant volatile organic compounds (VOCs) enables monitoring of pests and diseases in agriculture. We previously revealed that a localized surface plasmon resonance (LSPR) sensor coated with a molecularly imprinted sol-gel (MISG) can be used for cis-jasmone vapor detection. Although the selectivity of the LSPR sensor was enhanced by the MISG coating, its sensitivity was decreased. Here, gold nanoparticles (AuNPs) were doped in the MISG to enhance the sensitivity of the LSPR sensor through hot spot generation. The size and amount of AuNPs added to the MISG were investigated and optimized. The sensor coated with the MISG containing 20 μL of 30 nm AuNPs exhibited higher sensitivity than that of the sensors coated with other films. Furthermore, an optical multichannel sensor platform containing different channels that were bare and coated with four types of MISGs was developed to detect plant VOCs in single and binary mixtures. Linear discriminant analysis, k-nearest neighbor (KNN), and naïve Bayes classifier approaches were used to establish plant VOC identification models. The results indicated that the KNN model had good potential to identify plant VOCs quickly and efficiently (96.03&#37;). This study demonstrated that an LSPR sensor array coated with a AuNP-embedded MISG combined with a pattern recognition approach can be used for plant VOC detection and identification. This research is expected to provide useful technologies for agricultural applications.

DOI： 10.1021/acssensors.8b00329

Language：English   Publishing type：Research paper (scientific journal)  

Improving the efficiency of detecting the spatial distribution of gas information with a mobile robot is a great challenge that requires rapid sample collection, which is basically determined by the speed of operation of gas sensors. The present work developed a robot equipped with a highspeed gas sensor module based on localized surface plasmon resonance. The sensor module is designed to sample gases from an on-ground odor source, such as a footprint material or artificial odor marker, via a fine sampling tubing. The tip of the sampling tubing was placed close to the ground to reduce the sampling time and the effect of natural gas diffusion. On-ground ethanol odor sources were detected by the robot at high resolution (i.e., 2.5 cm when the robot moved at 10 cm/s), and the reading of gas information was demonstrated experimentally. This work may help in the development of environmental sensing robots, such as the development of odor source mapping and multirobot systems with pheromone tracing.

DOI： 10.1021/acssensors.8b00214

Language：English   Publishing type：Research paper (scientific journal)  

This work is an exploration into visualizing measurement of putrescine specific adsorption by photographing colorized molecule imprinting chromogenic hydrogel. Membranes are prepared with imitate templates 1,4-butylene glycol, adipic acid or succinic acid, respectively and ninhydrin is used as chromogenic agent for target molecule putrescine. The adsorbing concentration on MIP is reflected in the form of visible violet-colored stain differed in shape and shade, which are recorded by hyper spectral camera and proceeded into intuitive 3D isohypse surfaces plot. By quantifying the height of surface peaks, imprinting efficiency is estimated in accordance with polyvinyl alcohol concentration and crosslinking degree. The imprinting efficiency of three imitate molecule templates is also discussed. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2017.11.128

Language：English   Publishing type：Research paper (scientific journal)  

The detection and discrimination of volatile carboxylic acid components, which are the main contributors to human body odor, have a wide range of potential applications. Here, a quartz crystal microbalance (QCM) sensor array based on molecularly imprinted polymer (MIP) nanobeads is developed for highly sensitive and selective sensing of typical carboxylic acid vapors, namely: propionic acid (PA), hexanoic acid (HA) and octanoic acid (OA). The MIP nanobeads were prepared by precipitation polymerization with methacrylic acid (MAA) as a functional monomer, trimethylolproane trimethacrylate (TRIM) as a crosslinker, and carboxylic acids (PA, HA and OA) as the template molecules. The precipitation polymerization resulted in nano-sized (150-200 nm) polymer beads with a regular shape. The polymerization conditions were optimized to give a functional monomer, crosslinker, and template ratio of 1:1:2. We investigated the imprinting effect using both QCM and GC/MS measurements comparing vapor absorption characteristics between the imprinted and non-imprinted (NIP) nanobeads. A four-channel QCM sensory array based on the NIP and the three types of MIP nanobeads was fabricated for sensing the three types of carboxylic acid vapor at concentrations on the ppm level. The output of the sensor array was analyzed by both a non-supervised method (principle component analysis: PCA) and supervised method (linear discrimination analysis: LDA). LDA showed a better discrimination ability than PCA. A 96&#37;-classification rate was achieved by applying leave-one-out cross-validation to the LDA model. The high sensitivity and selectivity of the sensor array was attributed to the imprinting effect of the nano-sized polymer beads. The developed MIP nanobeads, together with other types of MIPs, show promise as materials for artificial receptors in vapor and odorant sensing.

DOI： 10.1016/j.aca.2018.01.004

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/olfactometry (GC/O) has been used in various fields as a valuable method to identify odor-active components from a complex mixture. Since human assessors are employed as detectors to obtain the olfactory perception of separated odorants, the GC/O technique is limited by its subjectivity, variability, and high cost of the trained panelists. Here, we present a proof-of-concept model by which odor information can be obtained by machine-learning-based prediction from molecular parameters (MPs) of odorant molecules. The odor prediction models were established using a database of flavors and fragrances including 1026 odorants and corresponding verbal odor descriptors (ODs). Physicochemical parameters of the odorant molecules were acquired by use of molecular calculation software (DRAGON). Ten representative ODs were selected to build the prediction models based on their high frequency of occurrence in the database. The features of the MPs were extracted via either unsupervised (principal component analysis) or supervised (Boruta, BR) approaches and then used as input to calibrate machine-learning models. Predictions were performed by various machine-learning approaches such as support vector machine (SVM), random forest, and extreme learning machine. All models were optimized via parameter tuning and their prediction accuracies were compared. A SVM model combined with feature extraction by BR-C (confirmed only) was found to afford the best results with an accuracy of 97.08&#37;. Validation of the models was verified by using the GC/O data of an apple sample for comparison between the predicted and measured results. The prediction models can be used as an auxiliary tool in the existing GC/O by suggesting possible OD candidates to the panelists and thus helping to give more objective and correct judgment. In addition, a machine-based GC/O in which the panelist is no longer needed might be expected after further development of the proposed odor prediction technique.

DOI： 10.1021/acs.analchem.7b02389

Language：English   Publishing type：Research paper (scientific journal)  

Detection of cis-jasmone (CJ) enables monitoring of growth pressure in plants, which is especially useful for sensing attacks by herbivores. Here, a sensitive and selective nanocomposite-imprinted, localized surface plasmon resonance (LSPR) sensor for CJ vapor was fabricated. Gold (Au) nano-islands were prepared by vacuum sputtering of Au nanoparticles on a glass substrate, followed by thermal annealing. Titanium molecularly imprinted sol-gels (MISGs) were spin-coated on the Au nano-islands as an adsorption layer for enhancing the selectivity of the optical sensor. Gas molecules were detected by using a small spectrometer to monitor variations in absorption spectra. In addition, the functional monomer and the ratio of matrix materials to functional monomers in the MISGs were investigated and optimized. MISGs that contained the functional monomer trimethoxyphenylsilane at a 3:1(v:v) ratio exhibited a higher sensitivity and selectivity than other films. The optical sensor would have advantages of low cost, selectivity, sensitivity, and repeatability. The limit of CJ detection in air was 3.5 ppm (signal/noise = 3). Thus, the sensor is expected to be a potential tool for CJ monitoring in agriculture applications.

DOI： 10.1016/j.snb.2017.12.123

Language：English   Publishing type：Research paper (scientific journal)  

Progress in the molecular biology of olfaction has revealed a close relationship between the structural features of odorants and the response patterns they elicit in the olfactory bulb. Molecular feature-related response patterns, termed odor maps (OMs), may represent information related to basic odor quality. Thus, studying the relationship between OMs and the molecular features of odorants is helpful for better understanding the relationships between odorant structure and odor. Here, we explored the correlation between OMs and the molecular parameters (MPs) of odorants by taking OMs from rat olfactory bulbs and extracting feature profiles of the corresponding odorant molecules. 178 images of glomerular activities in olfactory bulb that are corresponding to odorants were taken from the OdorMapDB, a publicly accessible database. The gray value of each pixel was extracted from the images (178 × 357 pixels) to fabricate an image matrix for each odorant. Forty-six molecular feature parameters were calculated using BioChem3D software, which was used to construct a second matrix for each odorant. Correlation analysis between the two matrixes was first carried out by establishing coefficient maps. Results from hierarchical clustering showed that all parameters could be segregated into seven clusters, and each cluster showed a relatively similar response pattern in the olfactory bulb. Using the information from the OMs and MPs, we mapped odorants in 2D space by incorporating dimension-reducing techniques based on principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE). Artificial neural network models based on the OM and MP feature values were proposed as a means to identify odorant functional groups. An OM-PCA-based model calibrated via extreme learning machine (ELM) was 94.81&#37; and 93.02&#37; accuracy for the calibration and validation sets, respectively. Similarly, an MP-t-SNE-based model calibrated by ELM was 86.67&#37; and 93.35&#37; accuracy for the calibration set and the validation set, respectively. Thus, this research supports a structure-odor relationship from a data-analysis perspective.

DOI： 10.1016/j.snb.2017.08.024

Language：Others   Publishing type：Research paper (scientific journal)  

Poly (3-hexylthiophene) (P3HT)/Au nano-islands composite was deposited on the interdigital microelectrode (IME) for the electrical conduction and gas sensing characteristics measurement. The conduction characteristic was verified to be Au nano-islands sputtering time dependent. Long sputtering time would form large-sized, closely-packed, and inter-connected Au nano-islands with irregular shape. As discussed in our previous work, there existed the mutual effects between the surface plasmon resonance of Au nano-islands and P3HT, which helped to increase the conduction. Herein, IME under 90 s Au sputtering and 60 °C heating presented the best gas sensing performance instead of longer sputtering time such as 150 s. This result implied that gas sensing characteristics of P3HT/Au nano-islands composite depended on the coupling condition between the localized surface plasmon resonance of Au nano-islands and P3HT molecules instead of the conductance characteristics.

DOI： 10.1016/j.snb.2016.10.030

Language：English   Publishing type：Research paper (scientific journal)  

Controlled orientation of metal nanostructures on a solid substrate was realized by irradiating a pre-deposited nanoseed layer with linearly polarized light in a growth solution containing metal cations. The resulted nanostructures showed the different transmittance spectra for two orthogonal polarized lights, which indicated an anisotropic growth induced by polarized light. The investigation on the growth conditions demonstrated that the wavelength of the irradiated light and the existence of cetyl cetyltrimethylammonium bromide used as surfactant could affect the anisotropic degree of the oriented nanostructures. It was suggested that the polarized lights enhanced the anisotropic local electric field of Au seed nanoparticles, which resulted in the oriented growth of metal nanostructures during the reduction process in the solution. The approach reported in this work can be used in the device fabrication based on oriented metal nanostructures, such as photocatalysts or optical sensors.

DOI： 10.1016/j.tsf.2016.11.039

Language：English   Publishing type：Research paper (scientific journal)  

Volatile organic acids are important compounds contained in human body odor. The detection and recognition of volatile organic acids in human body odor are significant in many areas. The present study explored a possibility to use localized surface plasmon resonance (LSPR) of Au nanoparticles (AuNPs) and molecularly imprinted sol-gels (MISGs) as the sensitive layer to recognize typical organic acid odorants, propanoic acid (PA), hexanoic acid (HA), heptanoic acid (HPA) and octanoic acid (OA), from human body. The LSPR layer was prepared by vacuum sputtering of AuNPs on a glass substrate and consequently thermal annealing. The sensitive layer was fabricated by spin-coating molecularly imprinted titanate sol-gel on the AuNPs layer. A homemade optical device was developed to detect the change of transmittance, which was caused by the index changes of organic acid vapors where selecting absorbed by the MISG layers. It was found that compared with MISG coated samples, samples coated with non-imprinted sol gel (NISG) shown no responses to any acid vapors. For the MISG coated sensors, the LSPR sensitivity was affected by the spin coating speed. In addition, a sensor array based on MISGs with different templates (HA, HPA and OA) was constructed to detect the organic acids in single and their binary mixtures. The sensor response was analyzed by principal component analysis (PCA) and linear discriminant analysis (LDA). A 100&#37; classification rate was achieved by leave-one-out cross-validation technique for LDA model. This work demonstrated that the MISGs coated LSPR sensor array has a great potential in organic acid odor recognition of human body odor.

DOI： 10.1016/j.snb.2017.04.048

Language：English   Publishing type：Research paper (scientific journal)  

α-Pinene is a kind of biomarker vapors emitted by plant during metabolism process. In this work, A localized surface plasmon resonance (LSPR) sensors based on the large and closely-packed Au nano-islands were propose to be coupled with the molecularly imprinted polymer (MIP) film for α-pinene vapor detection. Au nano-island film was prepared through repeated Au sputtering and annealing with cycles as many as 18. MIPα-pinene was prepared using methacylic acid as monomer, ethylene glycol dimethylacrylate as cross-linker, and α-pinene as the template molecule. Pre-polymerized MIPα-pinene solution was spin-coated on Au nano-island films at a series of speeds. The influence of spin coating speed on polymer thickness and target vapor binding capability was investigated. The result demonstrated that thick polymer layer could bind more template molecules than the thin one, which verified our speculation that there were more specific template binding sites in thick polymer layer. In addition, the in-situ response of MIPα-pinene coated Au nano-island film to α-pinene vapor was verified to be rapid (in less than 10 s) and reversible. The selective α-pinene vapor adsorption and absorption characteristics of MIPα-pinene coated Au nano-islands film to α-pinene vapor was observed comparing with the responses to γ-terpinene and limonene vapors.

DOI： 10.1016/j.snb.2016.03.117

Language：English   Publishing type：Research paper (scientific journal)  

A localized surface plasmon resonance gas sensor based on Au nano-island films coated with molecularly imprinted polymer (MIP) layer was developed to selectively detect terpene vapor emitted from plants. Au nano-islands were deposited on a glass substrate through repeated Au sputtering and annealing. The MIP layer was coated on Au nano-island films by spin-coating a pre-polymerized solution containing methacrylic acid as monomer, ethylene glycol dimethylacrylate as crosslinker, and α-pinene as the template molecule. The influence of nanostructure on the refractive index (RI) sensing characteristics was mainly investigated in this paper. The result demonstrated that the structure of Au nano-island films could be controlled by Au sputtering-annealing cycle. Increase in the sputteringannealing cycle induced the size increase and the inter-particle distance decrease of Au nano-island films. In addition, spectral red shift, decrease in transmittance, and increase in absorbance were observed under this procedure as well. The typical RI sensing evaluation parameters Δλmax, ΔTmin, and ΔAmax achieved the maximum values: 9.75 nm, and 9&#37;, 0.42 under 3 and 18 Au sputtering-annealing cycles. Au nano-island films under 3 and 18 Au sputtering-annealing cycles were coated with the MIP, and the response of MIP-coated Au nano-island sensor to α-pinene vapor was verified to be fast, reversible, and reproducible.

DOI： 10.1109/JSEN.2016.2536629

Language：English   Publishing type：Research paper (scientific journal)  

Gas sensing characteristics of Au nanoparticles (AuNPs)/3-hexylthiophene-2, 5-diyl (P3HT) composite based on photocurrent detection under different irradiation wavelengths were investigated. AuNPs with different structures were prepared either by the vacuum sputtering/annealing method or by the wet chemical synthesis based on seed growth. AuNPs/P3HT composites were prepared by the dip coating method. The optical features of P3HT and Au nanostructure/P3HT composite were investigated. The optical absorption increase of AuNPs film was observed after P3HT coating, which was attributed to the interaction between the P3HT and the Au nano-islands. New shoulder peaks and the phenomenon of one spectral peak splitting into two were observed in the absorption spectra of the composite film, which confirmed the interaction between the AuNPs and the P3HT further. The photoconductivity characteristics of the P3HT and AuNPs with spectral peak position at 580-nm (AuNPs580)/P3HT composite films were investigated utilizing LED light source with different dominate wavelengths. The wavelength-dependent photocurrent change ratio I/I0 of both the P3HT and the AuNPs580/P3HT composite films was observed. The maximum I/I0 of the P3HT and AuNPs580 composite films emerged under LED irradiation with a dominate wavelength 590 nm, which was mainly ascribed to the antenna effect from the Au nano-islands, the carrier injection from nanostucture to P3HT, localized surface plasmon resonance coupling among Au nanostructures, and plasmon coupling between the Au nano-islands and the P3HT molecules. The response of Au nano-island/P3HT composite to ethanol vapor showed that the response and recovery time was shorter than 2 s. Furthermore, gas sensing characteristics were verified to be irradiation wavelength dependent. Irradiation light source with a dominate wavelength 590 nm produced the largest I/I0 1.07.

DOI： 10.1109/JSEN.2015.2487278

Language：English   Publishing type：Research paper (scientific journal)  

A concept based on multispectral fluorescence imaging was proposed in this paper for the discrimination and visualization of odorants. Fluorescent dyes with different excitation/emission spectra were mixed into agarose gel to prepare a multiple probe sensing film. Odorants remained in environment were recorded on the sensing film via a process called odorant exposure. The odorant-induced fluorescence change of the film under various excitation lights was captured by a CCD camera to obtain multispectral images. It was demonstrated that the use of multiple fluorescence probes provided discrete emission bands, which increased the dimensions of vector space of the multispectral images. Complicated interactions between probes and probes, probes and odorants resulted in the diversiform fluorescence change patterns of the images. Combined with principal component analysis (PCA), different odorants could be discriminated and clustered in the principal component spaces in association with their molecular structures. A hand-shape odorant mark with region-segmented components was visualized with high spatial resolution. Additionally, the technique also succeeded in the visualized demonstration of an airflow containing mixed odorants. Compared with the existing gas and odor sensing technologies, the multispectral fluorescence imaging can be used not only to discriminate different odorants, but also to visualize their time-averaged spatial distribution in environment. Due to its novelty and high information acquisition ability, it can be expected as a new and powerful tool in odor sensing. (C) 2015 Elsevier By. All rights reserved.

DOI： 10.1016/j.snb.2015.07.073

Language：Others   Publishing type：Research paper (scientific journal)  

Localized surface plasmon resonance of noble metallic nanoparticles has been widely used in the fabrication of various sensors. Turning the nanostructure of localized surface plasmon resonance is significant because the resonance induced localized surface plasmon resonance shift is found to be strongly dependent on the structural characteristics, and thus the performance of the sensors. A simple sputtering, annealing, re-sputtering, and re-annealing process was proposed to tune the structural and optical characteristics of Au nano-islands deposited on the glass substrate. It was found that the size and inter-particle distance of nano-islands depend on annealing time and temperature. High temperature annealing tended to increase the size and inter-islands distance of Au islands. Re-sputtering and re-annealing under different conditions made size and inter-particle distance further tuning possible. Investigations on the optical characteristics of Au nano-islands demonstrated that the surface plasmon resonance peak and the spectral bandwidth of islands were tunable from 510 nm to 620 nm and from 50 nm to approximately 400 nm, respectively. The refractive index sensitivity of Au nano-islands determined by the surface plasmon band position change in different surrounding medium was compared. 500 °C 5 h annealing increased the value of refractive index sensitivity to approximately 58 nm/RIU from 26 nm/RIU under 100 °C 5 h annealing. Besides, Au nano-islands with the same re-sputtering condition but different re-annealing conditions showed the maximum value when the re-annealing temperature is at 500 °C for 5 h. In addition, the refractive index sensitivity, surface plasmon band position, and figure of merit were dependent with each other. These results suggest that the scheme "sputtering, annealing, re-sputtering, and re-annealing" is an effective method to adjust the structure and increase the refractive index sensitivity of sputtered Au islands.

DOI： 10.1016/j.vacuum.2014.09.005

Language：English  

Language：English  

DOI： 10.1109/JSEN.2013.2264803

Language：English  

DOI： 10.1016/j.jcis.2013.05.051

Language：English  

DOI： 10.1016/j.snb.2013.03.111

Language：English   Publishing type：Research paper (scientific journal)  

High-speed Gas Sensing using Localized Surface Plasmon Resonance of Sputtered Noble Metal Nanoparticles
High speed gas sensing devices can be applied in a number of areas where a better understanding of gas distribution is needed, such as in environmental monitoring and safety- and security-related fields. In this paper, we present a localized surface plasmon resonance (LSPR) sensor that was realized using sputtered Au and Ag nanoparticles (NPs), which can be used in robots for high-speed gas detection. The NPs' LSPR response, a red-shift of the minimum transmittance in wavelength (Δλ_min), and a decrease in the minimum transmittance (ΔT_min) for ethanol gas, were investigated and compared using Au and Ag NPs under the same sputtering conditions but using a different thermal annealing process for the reshaping of the NPs. The results obtained show that NPs with a larger aspect ratio can generate a large LSPR response. The response characteristics confirmed that this LSPR sensor can be used for high-speed gas detection.

DOI： 10.1541/ieejsmas.133.90

Language：English   Publishing type：Research paper (scientific journal)  

The detection of terpene vapors, a group of biomarker vapors emitted by plants during their growth process, is an efficient way to monitor plant growth status and control plant pests and disease. In this study, a gas sensor based on the localized surface plasma resonance (LSPR) of Au nanoparticles (Au NPs) is proposed for the terpene vapors detection. Au ion sputtering method is used to deposit Au NPs on transparent glass substrates. The dependence of transmission spectra on the morphology of Au NPs prepared by different sputtering conditions is investigated. In order to enhance the sensitivity and selectivity of the sensor, thiolate modification is applied to form the selective soluble monolayer on the surface of Au NPs. The results indicate that different thiolates could form different steric capping layers, and the responding ability of the LSPR sensor is verified by a red-shift of the minimum transmittance in wavelength (Δλ_min) and a decrease in the minimum transmittance (ΔT_min) upon exposure to terpene vapors.

DOI： 10.1109/JSEN.2012.2231672

Language：English  

DOI： 10.1016/j.ijhydene.2012.06.096

Language：English   Publishing type：Research paper (scientific journal)  

In this study, odor evaluation and discrimination are examined. First, an odor separating system that imitates the odor receptive mechanism of biological olfaction is developed. This system enables a rough detection of odor by measuring the molecular size and polarity of odorants. Using representative odor materials that belong to different biological glomeruli clusters, odor information extracted on time course patterns can be obtained by the system. The extracted features can be used for creating an odor map similar to the one created in the receptive mechanism, which can classify qualities by their odor-cluster attributes. Mixed odors can be discriminated and decomposed into their elemental clusters. The map obtained from this study can be used for odor matching analysis. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2012.03.041

Language：English   Publishing type：Research paper (scientific journal)  

By investigating the electrochemical nucleation and growth of polyaniline (PANI) on the insulating gap area of an interdigitated electrode, a template-free, in-situ approach is developed to obtain PANI nanowires and nanofibers with horizontal orientation on solid substrates. Experimental results show that the deposition process of PANI on the gap area is significantly influenced by polymerization conditions (such as polymerization current and time) and surface characteristics of the substrates (such as hydrophilicity/hydrophobicity and roughness). The concentration of solution-formed oligomers and the nucleation amount of the oligomers on the solid surface determine the morphology and orientation of the nanostructures. Controlling the deposition with high oligomer concentrations and limited nucleation amounts on the substrate is the key to the horizontal orientation. Gas sensing experiments confirm that the horizontal orientation of the nanostructures helps to improve the sensitivity and response time of sensor devices. Because of its simplicity, the approach proposed in this paper can be used in the fabrication of nanostructured conducting polymer chemiresistive gas sensor with high sensitivity but low cost. © 2011 American Chemical Society.

DOI： 10.1021/ma1023878

Language：English  

Language：English  

Detection of odor map image using optical method
Odor gas detection is important in explosives detection, environmental sensing, biometrics, foodstuff and more comfortable life. In this paper, we tried to detect odor chemicals with optical method. We used five kinds of fluorescence dyes, fluorescenin, acridine orange, pyrene, quinine sulfate, and tryptophan. As analyte, we used following four compounds, benezen, vanillin, and NPOE. It is supposed that PET or FRET mechanism will occur between fluorescence dyes and odor compounds, then fluorescence quenching will observed. Indeed, we could detect odor substances using fluorescence dyes by fluorescent quenching. Odor information could be obtained by response patterns across the fluorescence dyes. Moreover, we captured odor shape image and odor spatiotemporal images with cooled CCD camera. Shapes of target which emit odor could be roughly recognized by odor shape image. From the odor spatiotemporal images, two-dimensional odor expanse could be obtained.

DOI： 10.1299/jsmeicam.2010.5.165

Language：English   Publishing type：Research paper (scientific journal)  

In order to obtain practicable nano-conducting polymer resistive sensors, we investigated the electrochemical deposition of polyaniline (PANI) on the insulating gap area of an interdigitated electrode with a gap width as great as 100 μm. We revealed that the nucleation and growth of PANI on the insulating substrate were influenced by the surface character of the substrate such as hydrophilicity and roughness. By controlling the polymerization conditions, homogeneous PANI films with various nanostructures could be obtained across the insulating gap to form resistive junctions. Among them, a loose 2D nanowire network structure showed the best sensing performance upon exposure to ammonia gas with a low concentration. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elecom.2009.10.030

DOI： 10.1109/LSENS.2024.3432073

Web of Science

DOI： 10.1109/LSENS.2024.3419812

Web of Science

Language：Japanese   Publisher：Japan Association on Odor Environment  

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DOI： 10.2171/jao.55.89

CiNii Research

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：IEEE Sensors Letters  

Soft robots with flexible and elastic body substrates made of soft materials provide a high degree of freedom (DoF), adaptability, and interact well with their environment. In this letter, we developed a film-type soft microrobot equipped with an optical sensor, light source, and a 4-DoF gripper arm based on kinetic electronics. This optical sensor film robot can be used for object handling, gripping, and optical sensing operations. It presents considerable potential for the low-cost fabrication of microrobots that can perform complicated operations, such as object handling and optical sensing.

DOI： 10.1109/LSENS.2023.3303076

Web of Science

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researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of IEEE Sensors  

Visualizing invisible gas molecules can be a great help to our lives. At present, gas sensors can already visualize the spatial distribution of gas mixture, however, the visualization of a specific gas requires further analysis of the measurement data. In this study, matrix decomposition is used to analyze the measurement data of localized surface plasmon resonance (LSPR) gas sensor. To satisfy the linear relationship between the concentration of gas and the output of the device required for applying matrix decomposition, we formulated a procedure for processing the measurement data instead of using them directly. To obtain the diffusion trace of a specific gas, we designed a method to obtain the characteristic output of the specific gas, then by using the characteristic output as the known information, the corresponding diffusion trace can be estimated better through the matrix decomposition algorithm. We used the designed method to analyze the measurement data, and the results show that our method can obtain the spatial distribution of some gas.

DOI： 10.1109/SENSORS56945.2023.10324923

Web of Science

Scopus

Language：Japanese  

Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of IEEE Sensors  

Microbial volatile organic compounds (MVOCs) could be detected and used to understand the metabolic state of microorganisms. The gas sensor developed using the Surface Enhanced Raman Scattering (SERS) technique possesses ultra-high sensitivity and excellent selectivity, which is suitable for detecting low-concentration and complex MVOCs. Here, an odor source is simulated as a microbial community, and a 2D SERS sensor array is utilized to visualize the odor spatial distribution and localize the odor source. The Raman spectra of the odor adsorbed onto the sensor surface are collected after scanning the sensor array. A heatmap image is obtained by using the intensities of the characteristic peaks from the acquired Raman spectra. Thus, the odor spatial distribution is presented, and the localization of the odor source is determined by the image.

DOI： 10.1109/SENSORS56945.2023.10325081

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researchmap

Language：English   Publisher：Journal of Cheminformatics  

The relationships between molecular structures and their properties are subtle and complex, and the properties of odor are no exception. Molecules with similar structures, such as a molecule and its optical isomer, may have completely different odors, whereas molecules with completely distinct structures may have similar odors. Many works have attempted to explain the molecular structure-odor relationship from chemical and data-driven perspectives. The Transformer model is widely used in natural language processing and computer vision, and the attention mechanism included in the Transformer model can identify relationships between inputs and outputs. In this paper, we describe the construction of a Transformer model for predicting molecular properties and interpreting the prediction results. The SMILES data of 100,000 molecules are collected and used to predict the existence of molecular substructures, and our proposed model achieves an F1 value of 0.98. The attention matrix is visualized to investigate the substructure annotation performance of the attention mechanism, and we find that certain atoms in the target substructures are accurately annotated. Finally, we collect 4462 molecules and their odor descriptors and use the proposed model to infer 98 odor descriptors, obtaining an average F1 value of 0.33. For the 19 odor descriptors that achieved F1 values greater than 0.45, we also attempt to summarize the relationship between the molecular substructures and odor quality through the attention matrix.

DOI： 10.1186/s13321-022-00671-y

Web of Science

Scopus

PubMed

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (other academic)  

The integration of biosensing technology and soft robots can improve the diagnostic and therapeutic functions of bionic machines, and provide wearable devices with flexible, low-invasive, real-time monitoring biosensing functions. Here, a robotic electrochemical biosensor based on kinetic electronics technique was developed. The film robot is composed of a bimorph actuator layer and a biosensing function layer. The sensor function layer adopts sputtering technology to form a gold electrode, and is processed to form a Nafion-coated glucose oxidase electrode. The film robot could be used as a kinetic printed circuit for probe chips for biological and chemical experiments, and can realize bending action under an applied voltage of 5 V.

DOI： 10.1109/SENSORS47087.2021.9639682

Language：English   Publishing type：Research paper (other academic)  

This paper introduces a new method to fabricate a large - scale sensor array. By printing electrodes on photographic paper and making insulating layers, 6×6 arrays of sensors were obtained. Different gas selective can be printed in different units to detect different gases. Thus, production of multiple sensors in a small area with low cost was realized. On a piece of A4 photo paper, 30 sensor matrices can be printed at the same time. Each sensor array has 36 sensing units, thus theoretically identifying up to 36 gases. The sensor is suitable to be used in wearable devices to identify human skin gases due to its flexible substrate, low production cost and simple manufacturing process. In this experiment, molecular imprinted polymer (MIP) solution [1], carbon black (C.B.) conductive solution and insulating solution are prepared as ink, which can be used for ink-jet printer printing. This makes the method of developing the sensor more flexible. Compared with the sensor developed by micropipette to drop the MIP solution and C.B. conductive solution, the sensor developed by a printer has better uniformity.

DOI： 10.1109/SENSORS43011.2019.8956795

Language：English   Publishing type：Research paper (other academic)  

Mixture of gas molecules must be accurately detected for gas sensor. However, there are certain difficulties in identifying the type of gas and detecting its concentration by chemical sensors. SERS (Surface Enhanced Raman Scattering) is a promising method for high sensitive gas detection because of its ability of molecule discrimination. However, it is difficult for SERS sensor to identify gases with the similar structure. In this research, we have developed a more selective SERS sensor with molecular filter layers. Molecular filter property is studied by coating a filter polymer film on the SERS substrate. The characteristics of the sensor with two membrane structures were also studied and different filtering properties were obtained.

DOI： 10.1109/SENSORS43011.2019.8956884

Language：English   Publishing type：Research paper (other academic)  

Various odor robots have been developed for finding gas sources. However, the response speed of sensors is now a major limit for the promotion of odor robot using chemical substances information. In this research, we have developed a robot equipped with two LSPR (Localized Surface Plasmon Resonance) gas sensor module that can quickly respond to gas molecules at a high speed of above 25 Hz and set a specific algorithm for tracking the invisible odor line on the ground.

DOI： 10.1109/SENSORS43011.2019.8956599

Language：English   Publishing type：Research paper (other academic)  

LSPR (Localized Surface Plasmon Resonance) based 2D (2 Dimensional) gas imaging sensor system which can capture spatial distribution of each constituent of mixed gas have been developed. The gas image sensor detects the gas promoted optical changes occurred on the LSPR substrate by CCD camera. Basically, LSPR gas sensor does not have a molecular selectivity, then the identification of gas species is difficult. To overcome the disadvantage, pixelated LSPR substrate based on Au/Ag core-shell structure which has different gas response properties is fabricated by photo-induced metal growth by mask-less exposure system using a commercial video projector.

DOI： 10.1109/SENSORS43011.2019.8956635

Language：Japanese  

Multi-sample gas sensing and its parallel calibration technique by fluorescence hyperspectral imaging

Language：Japanese  

High speed LSPR gas sensor array utilized by color dye functionalized on AuNPs.

Language：Japanese  

Language：English   Publishing type：Research paper (other academic)  

This paper proposes a flexible gas sensor array system fabricated by full printing process, which can simultaneously monitor a variety of gases. The production of sensors using a low-cost, large-scale, high-speed printing technology throughout the process. Realizing the production of multiple sensors in a small area with low cost. Detection of a variety of gases using a sensor array. The results show that it is possible to make a full-printing gas sensor by acetylene carbon black (Φ20 nm) ink and molecularly imprinted polymer (MIP) ink; 36 sensors are formed on a 3cm-3cm paper; and the gases such as acetic acid and hexanoic acid are well recognized.

DOI： 10.1109/TRANSDUCERS.2019.8808512

Language：Others   Publishing type：Research paper (other academic)  

Visualization of the distribution of various gases makes us possible to recognize environmental circumstances, e.g., localization of dangerous chemical sources or human body odorants in the case of disaster scene. Localized surface plasmon resonance (LSPR) can detect various gases with changes of surrounding dielectric constant, and can be used gas sensor with high response / recovery speed and high spatial resolution, i.e., 2 dimensional LSPR gas sensor gas work as a gas image sensor device. The gas image sensor detects the gas distribution occurred on the LSPR substrate by an ordinal image sensor. The general LSPR gas sensor, however, does not have a molecular selectivity, then the identification of gas species is difficult. To overcome such disadvantages, pixelated LSPR substrate based on Au/Ag core-shell structure is fabricated by photo-induced growth by mask-less exposure system using a commercial video projector.

DOI： 10.1109/TRANSDUCERS.2019.8808591

Language：Others   Publishing type：Research paper (other academic)  

This paper proposes a flexible gas sensor array system fabricated by full printing process, which can simultaneously monitor a variety of gases. The production of sensors using a low-cost, large-scale, high-speed printing technology throughout the process. Realizing the production of multiple sensors in a small area with low cost. Detection of a variety of gases using a sensor array. The results show that it is possible to make a full-printing gas sensor by acetylene carbon black (Φ20 nm) ink and molecularly imprinted polymer (MIP) ink; 36 sensors are formed on a 3cm-3cm paper; and the gases such as acetic acid and hexanoic acid are well recognized.

DOI： 10.1109/TRANSDUCERS.2019.8808512

Language：English   Publishing type：Research paper (other academic)  

This paper presents a Localized Surface Plasmon Resonance (LSPR) based high speed gas sensor module for gas sensing applications, including visualization of invisible odor trail. Innovative claims include: (1) the use of a double layer film with Au/Ag nanoparticles for gas detection; (2) high speed response characteristic; and (3) visualization of odor trail pattern with high spatial resolution. The results show a significant change in reflection light with ethanol vapor; response speed of 1 second; and a clear image of visualized odor trail of letter "Q" of a 3 mm line width.

DOI： 10.1109/TRANSDUCERS.2019.8808400

Language：English   Publishing type：Research paper (other academic)  

Visualization of the distribution of various gases makes us possible to recognize environmental circumstances, e.g., localization of dangerous chemical sources or human body odorants in the case of disaster scene. Localized surface plasmon resonance (LSPR) can detect various gases with changes of surrounding dielectric constant, and can be used gas sensor with high response / recovery speed and high spatial resolution, i.e., 2 dimensional LSPR gas sensor gas work as a gas image sensor device. The gas image sensor detects the gas distribution occurred on the LSPR substrate by an ordinal image sensor. The general LSPR gas sensor, however, does not have a molecular selectivity, then the identification of gas species is difficult. To overcome such disadvantages, pixelated LSPR substrate based on Au/Ag core-shell structure is fabricated by photo-induced growth by mask-less exposure system using a commercial video projector.

DOI： 10.1109/TRANSDUCERS.2019.8808591

Language：English   Publishing type：Research paper (other academic)  

Odor space shapes or images that visualize spatial chemical information are new information that could not be used so far, and have wide application fields that use volatile chemical substances as information. Search for a person at the disaster sites, search for odor marks in forensic investigation, biometrics, medical diagnosis, environmental pollution sources and illegal drugs, dangerous goods detection, fire detection, and agriculture. In this paper, trials on odor imaging with newly developed opto-chemical sensor films with 2-dimensional geometry are described. The 2-dimensional chemical sensor has high potential for providing rich information about chemical substances based on extremely high-density chemical sensor fabricated on the film.

DOI： 10.1109/ISOEN.2019.8823549

Language：Others   Publishing type：Research paper (other academic)  

If we can quickly recognize the distribution of dangerous gases, it will be useful in places such as disaster scene. Localized surface plasmon resonance (LSPR) gas sensor is known as a gas sensor with high response / recovery speed and high spatial resolution. However, the general LSPR gas sensor does not have a molecular selectivity and it is difficult to identify the gas species. We made gas selected pixelated LSPR substrate based on Au/Ag core-shell structure by photo-induced growth by exposure system using the photomask.

DOI： 10.1109/ISOEN.2019.8823375

Language：Others   Publishing type：Research paper (other academic)  

Detection of volatile organic components (VOCs) is meaningful to agricultural field, bio recognition and so on. In this study, we developed an array type gas sensor to detect VOCs. This sensor is based on localized surface plasmon resonance (LSPR). Molecularly Imprinted Sol-Gels (MISG) were patterned on the surface of Au nano-islands to add molecular selectivity. The substrate is separated into 9 regions on AuNPs by using polyimide tape partitions and spin coating MISG solutions for each region. Multi channels sensor was fabricated with this substrate after this process. The sensor's sensitives were compared for each channel. The result indicated that the sensitivity of target gas channel was higher than into others.

DOI： 10.1109/ISOEN.2019.8823275

Language：Others   Publishing type：Research paper (other academic)  

Odor space shapes or images that visualize spatial chemical information are new information that could not be used so far, and have wide application fields that use volatile chemical substances as information. Search for a person at the disaster sites, search for odor marks in forensic investigation, biometrics, medical diagnosis, environmental pollution sources and illegal drugs, dangerous goods detection, fire detection, and agriculture. In this paper, trials on odor imaging with newly developed opto-chemical sensor films with 2-dimensional geometry are described. The 2-dimensional chemical sensor has high potential for providing rich information about chemical substances based on extremely high-density chemical sensor fabricated on the film.

DOI： 10.1109/ISOEN.2019.8823549

Language：Others   Publishing type：Research paper (other academic)  

One problem of machine-learning-based prediction of structure-odor relationship is that odorant molecules are usually labeled with ambiguous descriptors when they are collected from different sources. This study focused on the clustering of the odor descriptors by text mining approaches as well as the prediction of newly established labels from physicochemical parameters of the classified odorant molecules. An odor database was established by web scraping and transferred to a document-Term matrix including 4011 odorants and 100 odor descriptors. The clustering of the odor descriptors was carried out by using different co-occurrence matrix and clustering approaches. A hierarchical cluster analysis combined with a co-occurrence probability distribution matrix has shown good results in the descriptor clustering. The attribute labels of each class were established and then predicted from physicochemical parameters of the classified odorants by using random forest model. An average accuracy higher than 82.42&#37; was obtained, indicating the effectiveness of the proposed approaches for predicting structure-odor relationship.

DOI： 10.1109/ISOEN.2019.8823446

Language：Others   Publishing type：Research paper (other academic)  

The present study explored a probe type gas detection system which can be used to detect the gas conveniently. The gas sensing mechanism is utilizing Localized Surface Plasmon Resonance (LSPR) sensor which based on the reflected light change caused by the refractive index changes of gas where exposing to the metal nanoparticles layer. The LSPR layer was prepared by vacuum sputtering of AuNPs on a glass substrate, growing in silver growth solution and consequently thermal annealing. An optical system which composed of fiber probe, light source and spectrometer was developed to detect the change of reflected light. It was found that compared with incident light irradiating from metal nanoparticles side, glass side could obtain clearer spectra peak. In addition, a LSPR sensor which had 5 hours silver growth time has the best response to acetic acid gas. This work demonstrated that the reflection detection system has a great potential in gas detecting area.

DOI： 10.1109/ISOEN.2019.8823157

Language：Others   Publishing type：Research paper (other academic)  

Localized Surface Plasmon Resonance (LSPR) based gas sensor is a promising way to break the bottleneck of the sensing speed of traditional semiconductor gas senor for mobile robot use. In this study, we developed a two-dimensional gas visualization system based on LSPR phenomenon with Au/Ag nanoparticles for high speed and high spatial resolution sensing. The 9-hour silver growth on the surface of Au nanoparticles layer has been shown to reduce the influence of transmitted light (noise) on visualization while ensuring sensitivity. An invisible odor trace similar to letter 'U' with a line width of 3 mm was visualized by CCD camera through the LSPR sensor film. The intensity changes of the image every 1 second showed of the developed system's high response speed and spatial resolution.

DOI： 10.1109/ISOEN.2019.8823230

Language：English   Publishing type：Research paper (other academic)  

If we can quickly recognize the distribution of dangerous gases, it will be useful in places such as disaster scene. Localized surface plasmon resonance (LSPR) gas sensor is known as a gas sensor with high response / recovery speed and high spatial resolution. However, the general LSPR gas sensor does not have a molecular selectivity and it is difficult to identify the gas species. We made gas selected pixelated LSPR substrate based on Au/Ag core-shell structure by photo-induced growth by exposure system using the photomask.

DOI： 10.1109/ISOEN.2019.8823375

Language：English   Publishing type：Research paper (other academic)  

Detection of volatile organic components (VOCs) is meaningful to agricultural field, bio recognition and so on. In this study, we developed an array type gas sensor to detect VOCs. This sensor is based on localized surface plasmon resonance (LSPR). Molecularly Imprinted Sol-Gels (MISG) were patterned on the surface of Au nano-islands to add molecular selectivity. The substrate is separated into 9 regions on AuNPs by using polyimide tape partitions and spin coating MISG solutions for each region. Multi channels sensor was fabricated with this substrate after this process. The sensor's sensitives were compared for each channel. The result indicated that the sensitivity of target gas channel was higher than into others.

DOI： 10.1109/ISOEN.2019.8823275

Language：English   Publishing type：Research paper (scientific journal)  

A promising research to evaluate the quality of ripe banana during storage period by analyzing the variability of the volatile chemical components in odor from peels and flesh based on solid-phase microextraction-GC-MS characterization and statistical analysis has been discussed. A rapid increase of ethanol concentration in peels and flesh contributes to rotting of the banana. Specifically, occurrence of some compounds, including 1,2-dimethoxybenzene, 3,4-dimethoxybenzaldehyde, and isoeugenol, is an important feature of banana rotting. The decrease of 3-hydroxy-4-methoxybenzaldehyde concentration signifies a weakening of antiseptic, bactericidal, fungicidal, and antioxidant properties of banana. Besides, the principal component analysis (PCA) has been implemented in the discrimination of banana odor at different days of storage.

DOI： 10.1007/s12161-019-01435-5

Language：Japanese  

Language：English  

Currently, the development of smart systems for recognition and sensing of volatile organic compounds (VOCs) in medical, agricultural, biometric, security and safety, applications is an emerging research area. This review presents an introduction to the field of VOC recognition by analytical methods and sensing by chemical sensors. The role of pattern recognition methods in the analysis of sensor array response is briefly discussed. Besides, the electronic nose (E-Nose) system (a bio-inspired prototype of the natural olfaction system by combining a chemical sensor array and pattern recognition methods) and its significance for VOCs recognition and sensing in different applications is explained. The study concludes current constraint and future prospects of VOC recognition and sensing in real-time applications.

DOI： 10.1016/j.chemolab.2018.12.008

Language：English   Publishing type：Research paper (other academic)  

The microbeads shape sensor film was developed in this work combines fluorescent dye agents whose fluorescent intensity can be influenced in touch of a specific odor, and Molecular Imprinting Polymer. Like photographic films, the fluorescent dye microbeads film can visualize the odor gas diffusion with the CCD camera. To enhance the fluorescence intensity of Quinine Sulfate increases in the water environment, hydrogel was applied in the film. For developing multi-odor sensors, we made four kinds of fluorescent microbeads to test whether the interaction among fluorescent dyes happened. It turned out microbeads structure successfully remained characters of every fluorescent dye.

DOI： 10.1109/ICSENS.2018.8589830

Language：Others   Publishing type：Research paper (other academic)  

The microbeads shape sensor film was developed in this work combines fluorescent dye agents whose fluorescent intensity can be influenced in touch of a specific odor, and Molecular Imprinting Polymer. Like photographic films, the fluorescent dye microbeads film can visualize the odor gas diffusion with the CCD camera. To enhance the fluorescence intensity of Quinine Sulfate increases in the water environment, hydrogel was applied in the film. For developing multi-odor sensors, we made four kinds of fluorescent microbeads to test whether the interaction among fluorescent dyes happened. It turned out microbeads structure successfully remained characters of every fluorescent dye.

DOI： 10.1109/ICSENS.2018.8589830

Language：Others   Publishing type：Research paper (other academic)  

Patternable actuator film for monolithic soft micro robot process was developed. The film is consisted from thermal bimorph actuation layer and extra functional layer including driving heater layer and elastic mechanical buffer layer. A cantilever arm actuator fabricated by patterning the film was operated with 2 V applied voltage. Multi actuator device or micro robot can be fabricated without assembling process by appropriate patterning process with this film.

DOI： 10.1109/ICSENS.2018.8589717

Language：English   Publishing type：Research paper (other academic)  

Various odor robots have been developed for gas source localization in plume with specific algorithm. However, sensor response speed is now a major limit for the promotion of odor robot using chemical substances information. In this research, we have fabricated a Localized surface plasmon resonance based gas sensor which can show a quick response to gas molecular at a high speed of above 25Hz. The sensor was mounted on a mobile robot for gas sources detection successfully. Furthermore, a two-dimensional gas sensor based on the same technique was developed for visualization of spatial distribution of gas flow.

DOI： 10.1109/ICSENS.2018.8589909

Language：English   Publishing type：Research paper (other academic)  

Patternable actuator film for monolithic soft micro robot process was developed. The film is consisted from thermal bimorph actuation layer and extra functional layer including driving heater layer and elastic mechanical buffer layer. A cantilever arm actuator fabricated by patterning the film was operated with 2 V applied voltage. Multi actuator device or micro robot can be fabricated without assembling process by appropriate patterning process with this film.

DOI： 10.1109/ICSENS.2018.8589717

Language：English   Publishing type：Research paper (other academic)  

Various odor robots have been developed for gas source localization in plume with specific algorithm. However, sensor response speed is now a major limit for the promotion of odor robot using chemical substances information. In this research, we have fabricated a Localized surface plasmon resonance based gas sensor which can show a quick response to gas molecular at a high speed of above 25Hz. The sensor was mounted on a mobile robot for gas sources detection successfully. Furthermore, a two-dimensional gas sensor based on the same technique was developed for visualization of spatial distribution of gas flow.

DOI： 10.1109/ICSENS.2018.8589909

Language：English  

A robot equipped with a high-speed LSPR gas sensor module for collecting spatial odor information from on-ground invisible odor sources
Improving the efficiency of detecting the spatial distribution of gas information with a mobile robot is a great challenge that requires rapid sample collection, which is basically determined by the speed of operation of gas sensors. The present work developed a robot equipped with a highspeed gas sensor module based on localized surface plasmon resonance. The sensor module is designed to sample gases from an on-ground odor source, such as a footprint material or artificial odor marker, via a fine sampling tubing. The tip of the sampling tubing was placed close to the ground to reduce the sampling time and the effect of natural gas diffusion. On-ground ethanol odor sources were detected by the robot at high resolution (i.e., 2.5 cm when the robot moved at 10 cm/s), and the reading of gas information was demonstrated experimentally. This work may help in the development of environmental sensing robots, such as the development of odor source mapping and multirobot systems with pheromone tracing.

DOI： 10.1021/acssensors.8b00214

Language：English   Publishing type：Research paper (scientific journal)  

In this short review, we describe our recent approaches and strategies for the development of quartz crystal microbalance (QCM)-based odor sensor systems for environmental and human health monitoring. QCM electrodes, which were modified with sensitive nanometerthick coatings via layer-by-layer (LbL) deposition, were used to develop a system for measuring significant environmental changes in indoor air. Identification of the origin of environmental changes was possible via the differential signal analysis of obtained data. The sensors showed different responses to humidity changes, hazardous gas (ammonia), or cigarette smoke exposure. In addition, QCM sensors with porous films comprising silica nanoparticles and poly(allylamine hydrochloride) (PAH) were fabricated via an electrostatic self-assembly method and they exhibited considerable sensitivity to relative humidity (RH). The infusion of poly(acrylic acid) (PAA) into the multilayer porous film enabled the construction of a highly sensitive and selective QCM sensor device for the detection of gaseous ammonia. Two types of QCM sensors, with and without PAA, enabled the simultaneous quantitative detection of humidity and ammonia. Preliminary tests were conducted to detect low concentrations of ammonia in human breath, which are of clinical relevance. The results obtained showed that the sensor can detect ammonia in human breath at pathological levels (greater than 3 ppm).

DOI： 10.18494/SAM.2018.1734

Language：English   Publishing type：Research paper (other academic)  

The detection of cis-jasmone is meaningful to sense potential threat in agriculture. In present study, a nanocomposite imprinted LSPR sensor was developed for determination of cis-jasmone vapors. Molecular imprinted sol-gels (MISG) were fabricated on the surface of Au nano-islands via spinning coating. For enhancing the sensitives of sensors, AuNPs was sputtered on the MISG layers. The sensitives and selectivelies of samples recoated divers thickness of AuNPs were compared and discussed. The result indicated that the sensitivity of AuNPs/MISG/AuNPs was higher than that of AuNPs/MISG. In addition, AuNPs/MISG coated with 3 nm AuNPs shown a better sensitive and selectively. In-situ response was verified to be fast, selective and reversible. The absorbance spectra of cis-jasmone vapors linearly increased with its concentration in the range of 10 to 75 ppm, with the limit of detection of 3.45 ppm (S/N=3). The research offered useful technologies for developing cis-jasmone sensor in agriculture area.

DOI： 10.1109/ICSENS.2017.8234422

Language：English   Publishing type：Research paper (other academic)  

Odor imaging sensor was developed with odorants sensing mechanism based on the complicated fluorescence interactions between the multi-fluorescent-probes and odorants. In this research, poly vinyl chloride (PVC) films including various fluorescent probe were developed, and fluorescence properties of the film were investigated. Using the multi fluorescent probe film, fluorescence intensity change spectrum to various odorants was measured, and odorants could be clustered by their chemical structure by multi-variate analyses of hyper spectra images.

DOI： 10.1109/ICSENS.2017.8234328

Language：English   Publishing type：Research paper (scientific journal)  

In the present study, body odor samples have been collected according to different sampling protocols and characterized using the gas chromatography (GC)–mass spectrometry (MS) technique with the objective to investigate the existence of different volatile organic compounds (VOCs) belonging to several chemical classes in body odor composition. Moreover, the characterization outcomes have been validated by analyzing spectral information using substantial clustering methods. Specifically, the data matrix based on peak height of chemical compounds in each experiment has been analyzed by using six clustering methods, including principal component analysis (PCA), k-means clustering, fuzzy c-means clustering, hierarchical cluster analysis, fuzzy clustering, and k-medoids clustering. Chemical compounds were well clustered into several groups with each of the implemented clustering methods which endorse the experimental characterization outcomes and establishes the existence of VOCs from multiple chemical classes in body odor composition.

DOI： 10.1016/j.ijms.2017.09.010

Language：English   Publishing type：Research paper (international conference proceedings)  

The detection of cis-jasmone is meaningful to sense potential threat in agriculture. In present study, a nanocomposite imprinted LSPR sensor was developed for determination of cis-jasmone vapors. Molecular imprinted sol-gels (MISG) were fabricated on the surface of Au nano-islands via spinning coating. For enhancing the sensitives of sensors, AuNPs was sputtered on the MISG layers. The sensitives and selectivelies of samples recoated divers thickness of AuNPs were compared and discussed. The result indicated that the sensitivity of AuNPs/MISG/AuNPs was higher than that of AuNPs/MISG. In addition, AuNPs/MISG coated with 3 nm AuNPs shown a better sensitive and selectively. In-situ response was verified to be fast, selective and reversible. The absorbance spectra of cis-jasmone vapors linearly increased with its concentration in the range of 10 to 75 ppm, with the limit of detection of 3.45 ppm (S/N=3). The research offered useful technologies for developing cis-jasmone sensor in agriculture area.

DOI： 10.1109/ICSENS.2017.8234422

Language：English   Publishing type：Research paper (other academic)  

Odor imaging sensor was developed with odorants sensing mechanism based on the complicated fluorescence interactions between the multi-fluorescent-probes and odorants. In this research, poly vinyl chloride (PVC) films including various fluorescent probe were developed, and fluorescence properties of the film were investigated. Using the multi fluorescent probe film, fluorescence intensity change spectrum to various odorants was measured, and odorants could be clustered by their chemical structure by multi-variate analyses of hyper spectra images.

DOI： 10.1109/ICSENS.2017.8234328

Language：Japanese  

Language：Japanese  

Language：Others   Publishing type：Research paper (other academic)  

We developed a dynamic photo-tunable gas adsorbent based on smart (photo sensitive) material and molecularly imprinted polymer (MIP) technology [1]. Gas adsorption property of the material, mixture of photochromic materials and polymethyl methacrylate (PMMA), can be controlled reversible and continuously by irradiation of with light different wavelength. As a result, gas sensor which is composed of a quartz crystal microbalance (QCM) coated with the developed adsorbent was fabricated. This sensor system can detect a certain gas molecule corresponding to the adsorbent property from gas mixture with only one sensor node.

DOI： 10.1109/TRANSDUCERS.2017.7994313

Language：Japanese  

Evaluation of gas penetration property of plasmonic sensor with molecular selective layer

Language：Japanese  

Gas separator based on gas adsorption-desorption and ventilation sequence

Language：English   Publishing type：Research paper (scientific journal)  

Present study deals with the operation of filter based approaches for selection of an optimal subset of peaks of chemical compounds in gas chromatography (GC)-mass spectrometry (MS) spectra with the objective to robust classification modeling of human body odor. Particularly, we have employed four filter based approaches including CFS, Linear-correlation, Rank-correlation, and Relief, in the selection of significant peaks and compared their performance. Selected subsets have been validated for qualitative and quantitative classification of human body odor samples in principal component (PC) space. Filter schemes were validated by analyzing sixteen decisive odor data sets obtained through characterization of body odor samples by GC–MS in four different experiments. Every feature filtering method results in an optimal subset of peaks for each data set. Efficiency of a particular subset of peaks has been evaluated by using them in PC analysis, and thereafter on the basis of visual discrimination as well inter-class separation (b) and intra-class (a) separation in PC space. Few methods result in a common subset of peaks for some data sets, though the maximum value of b and a minimum value of a has been obtained for discrimination amongst body odor samples by using selected subsets of peaks compare to all peaks in spectra. Best human body odor class discrimination outcomes have been achieved by using peaks of chemical compounds selected by Relief and CFS filters.

DOI： 10.1016/j.ijms.2017.03.003

Language：English   Publishing type：Research paper (scientific journal)  

The detection and recognition of metabolically derived aldehydes, which have been identified as important products of oxidative stress and biomarkers of cancers; are considered as an effective approach for early cancer detection as well as health status monitoring. Quartz crystal microbalance (QCM) sensor arrays based on molecularly imprinted sol-gel (MISG) materials were developed in this work for highly sensitive detection and highly selective recognition of typical aldehyde vapors including hexanal (HAL); nonanal (NAL) and bezaldehyde (BAL). The MISGs were prepared by a sol-gel procedure using two matrix precursors: tetraethyl orthosilicate (TEOS) and tetrabutoxytitanium (TBOT). Aminopropyltriethoxysilane (APT); diethylaminopropyltrimethoxysilane (EAP) and trimethoxy-phenylsilane (TMP) were added as functional monomers to adjust the imprinting effect of the matrix. Hexanoic acid (HA); nonanoic acid (NA) and benzoic acid (BA) were used as psuedotemplates in view of their analogous structure to the target molecules as well as the strong hydrogen-bonding interaction with the matrix. Totally 13 types of MISGs with different components were prepared and coated on QCM electrodes by spin coating. Their sensing characters towards the three aldehyde vapors with different concentrations were investigated qualitatively. The results demonstrated that the response of individual sensors to each target strongly depended on the matrix precursors; functional monomers and template molecules. An optimization of the 13 MISG materials was carried out based on statistical analysis such as principle component analysis (PCA); multivariate analysis of covariance (MANCOVA) and hierarchical cluster analysis (HCA). The optimized sensor array consisting of five channels showed a high discrimination ability on the aldehyde vapors; which was confirmed by quantitative comparison with a randomly selected array. It was suggested that both the molecularly imprinting (MIP) effect and the matrix effect contributed to the sensitivity and selectivity of the optimized sensor array. The developed MISGs were expected to be promising materials for the detection and recognition of volatile aldehydes contained in exhaled breath or human body odor.

DOI： 10.3390/s17020382

Language：English   Publishing type：Research paper (other academic)  

Highly sensitive optical sensing of molecules can be achieved by using localized surface plasmon generated at metal nanostructures, such as SERS-based sensing. We fabricated SERS-active silver nanostructures by using polarized light irradiation, and evaluated their response properties to rhodamine 6G. In this paper, it is shown that strong Raman signals of rhodamine 6G and large variation in optical transmission have been obtained. Especially, the transmission spectra of the silver nanostructures grown under the irradiation of polarized light showed unique polarizing properties derived from different modes of localized surface plasmons, which would be useful in smart optical sensing.

DOI： 10.1109/ICSENS.2016.7808850

Language：Others   Publishing type：Research paper (other academic)  

Gas sensor with high molecular selectivity is highly demanded in many fields of industry or disaster relief. Molecularly imprinted polymer (MIP) can recognize target gas by specific adsorption for template molecule. In this study, a novel chemiresistor, gas sensor which combined with MIP and conductive nanoparticles has been developed. The gases were distinguished based on molecularly structure by MIP. If gas molecule is absorbed into this polymer, structures and properties of conductive composites are changed. It causes electric resistance changed. It is conceivable that the degree of resistance change is dependent upon the amount of absorption. Moreover, MIP absorbs larger quantity of template molecule than similar gas molecule. So this MIP chemiresistor can be used for measurement of specific target gas based on magnitude of response. Measurement results of gas sensing showed that larger response was produced by MIP chemiresistor for the template molecule than other gas and NIP (non-imprinted polymer) composite. It means that a sensor which could both recognizing molecules and transduce electrical signal simultaneously was successfully developed.

DOI： 10.1109/ICSENS.2016.7808660

Language：Others   Publishing type：Research paper (other academic)  

Highly sensitive optical sensing of molecules can be achieved by using localized surface plasmon generated at metal nanostructures, such as SERS-based sensing. We fabricated SERS-active silver nanostructures by using polarized light irradiation, and evaluated their response properties to rhodamine 6G. In this paper, it is shown that strong Raman signals of rhodamine 6G and large variation in optical transmission have been obtained. Especially, the transmission spectra of the silver nanostructures grown under the irradiation of polarized light showed unique polarizing properties derived from different modes of localized surface plasmons, which would be useful in smart optical sensing.

DOI： 10.1109/ICSENS.2016.7808850

Language：Others   Publishing type：Research paper (other academic)  

Various devices are developed to obtain information of odor for crisis evasion in dangerous situation. However, the improvement of sensing methodology is lagging. Therefore, some novel odor sensors with high sensitivity, selectivity and short response time are required. Gas detection based on surface enhanced Raman scattering (SERS) is a promising technology to realize such sensor. We developed a sandwich structured SERS substrate with an organic layer, which was placed between an Au thin layer and a gold nano particles (AuNPs) layer. Furthermore, the organic layer was reconfigured to molecularly imprinted polymer (MIP) for selective gas detection. Raman spectrum obtained with a MIP-SERS substrate shows the appearance of peak based on 2-phenylethanol that is targeted gas molecule. Compared with non-imprinted polymer (NIP), MIP substrate showed stronger SERS signals.

DOI： 10.1109/ICSENS.2016.7808604

Language：English   Publishing type：Research paper (other academic)  

Various devices are developed to obtain information of odor for crisis evasion in dangerous situation. However, the improvement of sensing methodology is lagging. Therefore, some novel odor sensors with high sensitivity, selectivity and short response time are required. Gas detection based on surface enhanced Raman scattering (SERS) is a promising technology to realize such sensor. We developed a sandwich structured SERS substrate with an organic layer, which was placed between an Au thin layer and a gold nano particles (AuNPs) layer. Furthermore, the organic layer was reconfigured to molecularly imprinted polymer (MIP) for selective gas detection. Raman spectrum obtained with a MIP-SERS substrate shows the appearance of peak based on 2-phenylethanol that is targeted gas molecule. Compared with non-imprinted polymer (NIP), MIP substrate showed stronger SERS signals.

DOI： 10.1109/ICSENS.2016.7808604

Language：English   Publishing type：Research paper (other academic)  

Gas sensor with high molecular selectivity is highly demanded in many fields of industry or disaster relief. Molecularly imprinted polymer (MIP) can recognize target gas by specific adsorption for template molecule. In this study, a novel chemiresistor, gas sensor which combined with MIP and conductive nanoparticles has been developed. The gases were distinguished based on molecularly structure by MIP. If gas molecule is absorbed into this polymer, structures and properties of conductive composites are changed. It causes electric resistance changed. It is conceivable that the degree of resistance change is dependent upon the amount of absorption. Moreover, MIP absorbs larger quantity of template molecule than similar gas molecule. So this MIP chemiresistor can be used for measurement of specific target gas based on magnitude of response. Measurement results of gas sensing showed that larger response was produced by MIP chemiresistor for the template molecule than other gas and NIP (non-imprinted polymer) composite. It means that a sensor which could both recognizing molecules and transduce electrical signal simultaneously was successfully developed.

DOI： 10.1109/ICSENS.2016.7808660

Language：English   Publishing type：Research paper (scientific journal)  

Versatile odor sensors that can discriminate among huge numbers of environmental odorants are desired in many fields, including robotics, environmental monitoring, and food production. However, odor sensors comparable to an animal's nose have not yet been developed. An animal's olfactory system recognizes odor clusters with specific molecular properties and uses this combinatorial information in odor discrimination. This suggests that measurement and clustering of odor molecular properties (e.g., polarity, size) using an artificial sensor is a promising approach to odor sensing. Here, adsorbents composed of composite materials with molecular recognition properties were developed for odor sensing. The selectivity of the sensor depends on the adsorbent materials, so specific polymeric materials with particular solubility parameters were chosen to adsorb odorants with various properties. The adsorption properties of the adsorbents could be modified by mixing adsorbent materials. Moreover, a novel molecularly imprinted filtering adsorbent (MIFA), composed of an adsorbent substrate covered with a molecularly imprinted polymer (MIP) layer, was developed to improve the odor molecular recognition ability. The combination of the adsorbent and MIP layer provided a higher specificity toward target molecules. The MIFA thus provides a useful technique for the design and control of adsorbents with adsorption properties specific to particular odor molecules.

DOI： 10.3390/s16111974

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Versatile odor sensors that can discriminate among huge numbers of environmental odorants are desired in many fields, including robotics, environmental monitoring, and food production. However, odor sensors comparable to an animal’s nose have not yet been developed. An animal’s olfactory system recognizes odor clusters with specific molecular properties and uses this combinatorial information in odor discrimination. This suggests that measurement and clustering of odor molecular properties (e.g., polarity, size) using an artificial sensor is a promising approach to odor sensing. Here, adsorbents composed of composite materials with molecular recognition properties were developed for odor sensing. The selectivity of the sensor depends on the adsorbent materials, so specific polymeric materials with particular solubility parameters were chosen to adsorb odorants with various properties. The adsorption properties of the adsorbents could be modified by mixing adsorbent materials. Moreover, a novel molecularly imprinted filtering adsorbent (MIFA), composed of an adsorbent substrate covered with a molecularly imprinted polymer (MIP) layer, was developed to improve the odor molecular recognition ability. The combination of the adsorbent and MIP layer provided a higher specificity toward target molecules. The MIFA thus provides a useful technique for the design and control of adsorbents with adsorption properties specific to particular odor molecules.

DOI： 10.3390/s16111974

Language：English   Publishing type：Research paper (scientific journal)  

The focus of the present study is the human body odour recognition by analysis of information about the chemical compounds identified in their gas chromatography–mass spectrometry (GC–MS) chromatogram. The Artificial neural network (ANN) technique implemented in the current study, has been comprehensively used for classification and regression tasks in numerous applications. The experimental data set includes intensity characteristics (peak height, peak area, ratio of peak area and height) of several chemical compounds detected in GC–MS chromatogram of twenty odour samples (from four persons), and two non-body odour samples. The raw data set is transformed with logarithmic scaling, principal component analysis (PCA), and kernel principal component analysis (KPCA) in search of the better features by extracting. After preprocessing of data, feed forward back-propagation neural network (BPNN) technique is used in discrimination of body and non-body odour samples, as well as recognition of body odour to an individual. Although ANN classifier is optimized for the number of neurons, and training algorithms, the classification result is unstable and unsatisfactory (maximum correct classification rate 78&#37; and minimum correct classification rate 44&#37;). To improve the stability and accuracy of ANN classification results, data fusion approach is attempted. Eight different weighted and unweighted decision schemes of data fusion have been implemented in body odour recognition. Amongst them simple weighted vote (SWV), quadratic best worst weighted vote (QBWWV), and best worst weighted vote (BWWV) outperform with 100&#37; class recognition outcomes, compared with a single ANN classifier.

DOI： 10.1016/j.ijms.2016.06.002

Language：English  

Language：English  

Language：English  

Language：Japanese  

C-13-2 Plant odorants visualization based on optical sensing

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we demonstrated a new approach for gas sensing using multilayer films selfassembled with cationic gold nanoparticles (AuNPs+) and anionic polyelectrolytes via layerby- layer (LbL) deposition. The surface of AuNPs+ was modified with a cationic disulfide, [-S(CH₂)₂NHCO(CH₂)10(CH₃)3N⁺Br^-]₂. Two types of LbL film using AuNPs+ were selfassembled with anionic polyelectrolytes, poly(acrylic acid) (PAA), and poly(sodium 4-styrene sulfonate) (PSS) on quartz substrates, and their film growth was confirmed by UV-vis measurements. The 10-cycle AuNPs+/PAA ilm showed reproducible responses after exposure to ammonia gas (3000 ppm) and HCl treatment (0.1 M), showing absorbance changes of 0.0428 ± 0.0033 at 299 nm and 0.0053 ± 0.0013 at 544 nm for ive repeated tests. On the other hand, no signiicant changes were observed for the 10-cycle AuNPs+/PSS ilm. Ammonia binding was based on the acid-base interaction between ammonia and the free carboxylic acid groups of PAA. The ilm's composition and morphology were also investigated by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) measurements to clarify the sensing mechanism.

DOI： 10.18494/SAM.2016.1168

Language：English   Publishing type：Research paper (scientific journal)  

Odorant visualization based on luorescence imaging has been developed as a novel technique to obtain spatiotemporal information on odors in an environment. In order to increase the selectivity and reversibility of sensing films, fluorescent-dyed micropowders with molecular imprinting ability were proposed for the odorant visualization. The micropowders were prepared by bulk polymerization in the presence of template and luorescence probe molecules. The luorescence emission character and the molecular imprinting effect of the prepared micropowders were investigated by luorescence microscope observations and gas chromatography-mass spectrometry (GC/MS) measurements, respectively. The dyed molecular imprinted polymer (MIP) micropowders were coated on glass substrates and used as the sensing ilm for the selective visualization of odorant lows. The molecular imprinting effect was conirmed by the change in the ratio of the luorescence of the MIP ilm to the non-imprinted polymer (NIP) ilm. In addition, a higher ratio was demonstrated by the MIP ilm on the target odorant than the non-target odorant, which veriied the selective visualization of the prepared micropowder. The ilm also showed advantage in reversible response on various odorants; therefore the luorescent MIP micropowder can be used repeatedly in the real time odorant visualizaiton.

DOI： 10.18494/SAM.2016.1167

Language：English  

Preface to the special issue on "selected papers in the technical meetings on sensors and micromachines 2015"

DOI： 10.1541/ieejsmas.136.133

Language：English   Publishing type：Research paper (other academic)  

Sensitivity of optical sensing can be enhanced using assistance of plasmon generated at metal nanostructures, like SERS-based sensing. The growth process of metal nanoparticles which can control both shape and orientation on substrates in one step is required to solve the problem of the arrangement of pre-synthesized metal nanorods or other nanostructures to the surface of substrates in specific orientation. In this study, the procedure of polarized-light-directed growth of metal nanoparticles fixed on glass substrates in direct way is proposed, in which the irradiation of linearly polarized light to pre-deposited gold seeds on substrate, in immersing the substrates in the growth solution containing metal cations (gold or silver ions) and reducing agents. Consequently the anisotropic nanostructures whose orientation angle was in accordance with polarization direction in growth process were obtained. The evaluation of the resulted structures was performed with UV-vis spectrometer and scanning electron microscope.

DOI： 10.1109/ICSENS.2015.7370643

Language：English   Publishing type：Research paper (other academic)  

Localized surface plasmon resonance (LSPR) of metal nanoparticles (MNPs) causes strong light absorption and scattering, and the intensity changes are corresponding to refractive index of medium. Our research demonstrates that the spatial distribution of a gas flow can be visualized by observation of transmitted/scattered light of a LSPR-film which consists of two-dimensional arrangement of gold nanoparticles (AuNPs). In this study, to improve the visualization ability of LSPR-films, AuNPs are prepared under different conditions of annealing temperature and re-sputtering times. The LSPR character and gas responding ability are investigated. The results show that LSPR-film with annealing temperature 200°C and 3 times of sputtering shows the best performance. The film has ability to visualize the gas flow of ethanol with a concentration of 400ppm. It is suggested that high visualization ability can be achieved by controlling the distance of neighboring nanoparticles.

DOI： 10.1109/ICSENS.2015.7370180

Language：English  

DOI： 10.1109/ICSENS.2015.7370176

Language：English   Publishing type：Research paper (international conference proceedings)  

Sensitivity of optical sensing can be enhanced using assistance of plasmon generated at metal nanostructures, like SERS-based sensing. The growth process of metal nanoparticles which can control both shape and orientation on substrates in one step is required to solve the problem of the arrangement of pre-synthesized metal nanorods or other nanostructures to the surface of substrates in specific orientation. In this study, the procedure of polarized-light-directed growth of metal nanoparticles fixed on glass substrates in direct way is proposed, in which the irradiation of linearly polarized light to pre-deposited gold seeds on substrate, in immersing the substrates in the growth solution containing metal cations (gold or silver ions) and reducing agents. Consequently the anisotropic nanostructures whose orientation angle was in accordance with polarization direction in growth process were obtained. The evaluation of the resulted structures was performed with UV-vis spectrometer and scanning electron microscope.

DOI： 10.1109/ICSENS.2015.7370643

Language：English   Publishing type：Research paper (international conference proceedings)  

Localized surface plasmon resonance (LSPR) of metal nanoparticles (MNPs) causes strong light absorption and scattering, and the intensity changes are corresponding to refractive index of medium. Our research demonstrates that the spatial distribution of a gas flow can be visualized by observation of transmitted/scattered light of a LSPR-film which consists of two-dimensional arrangement of gold nanoparticles (AuNPs). In this study, to improve the visualization ability of LSPR-films, AuNPs are prepared under different conditions of annealing temperature and re-sputtering times. The LSPR character and gas responding ability are investigated. The results show that LSPR-film with annealing temperature 200°C and 3 times of sputtering shows the best performance. The film has ability to visualize the gas flow of ethanol with a concentration of 400ppm. It is suggested that high visualization ability can be achieved by controlling the distance of neighboring nanoparticles.

DOI： 10.1109/ICSENS.2015.7370180

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

The present study explores individual identity perception by analyzing the chemical peak information in the gas chromatography-mass spectrometry (GC-MS) spectra of body odor samples with standard data mining approaches. Mainly, the principal component analysis (PCA) method is chosen for the visual discrimination of the body odor samples in feature space. PCA in combination with the support vector machine (SVM) method is used for quantitative recognition. GC-MS characterization confirms the composition of numerous chemical species (aldehydes, acids, ketones, esters, sulfides etc.) in the body odor samples. The GC-MS spectra of body odor samples from the armpit and neck of three people (from dissimilar age groups) at two different sampling times (0 h and 4 h) were recorded in the experiment. A few blank (non-body odor) samples were also characterized with GC-MS and included as references in further analysis by the data mining methods. The discrimination efficiency (both qualitative and quantitative) for the individual body odors was evaluated for (i) three variables of chemical information in the GC-MS spectra (the peak area, peak height and ratio of peak area to height); (ii) two sampling times (0 h and 4 h); and (iii) two sampling parts of the body (the neck and armpit). The best visual discrimination of the individual body odors has been achieved using the peak height as a variable for the neck odor with a sampling time of 4 h. This result has been established with class separability measures calculated with principal component (PC) scores and SVM classification outcomes (86%).

DOI： 10.1039/C5AY02457A

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese  

Visualization of odorant in tomato using fluorescent polymer beads

DOI： 10.11527/jceeek.2015.0_396

Language：Japanese  

DOI： 10.1541/ieejsmas.135.299

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Quartz crystal microbalance (QCM) sensor array was developed for multi-purpose human respiration assessment. The sensor system was designed to provide feedback for human respiration. Thorough optimization of measurement conditions: air flow, temperature in the QCM chamber, frequency measurement rate, and electrode position regarding to the gas flow—was performed. As shown, acquisition of respiratory parameters (rate and respiratory pattern) could be achieved even with a single electrode used in the system. The prototype system contains eight available QCM channels that can be potentially used for selective responses to certain breath chemicals. At present, the prototype machine is ready for the assessment of respiratory functions in larger populations in order to gain statistical validation. To the best of our knowledge, the developed prototype is the only respiratory assessment system based on surface modified QCM sensors.

DOI： 10.3390/s150818834

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Drug of abuse or illicit drugs have become a serious health issue and global evils during the last few decades. Their detection is a significant area of research, for preventing illegal traffic and toxic effects on human health and society. Numerous analytical methods, based on diverse principles, have been developed for the detection of drugs of abuse. The core intention of present review is to pioneer the reader with the varieties of drugs of abuses (availability, formation, and use and ill-use) as well detection techniques developed and employed in the past few years. The study includes a comparative review of analytical detection techniques. Effectiveness of chemical sensors over other analytical techniques is particularly emphasized.

DOI： 10.2174/1385272819666150318223054

Language：English   Publishing type：Research paper (scientific journal)  

In present work, a novel quartz crystal microbalance (QCM) sensor array has been developed for prompt identification of primary aldehydes in human body odor. Molecularly imprinted polymers (MIP) are prepared using the polyacrylic acid (PAA) polymer matrix and three organic acids (propenoic acid, hexanoic acid and octanoic acid) as template molecules, and utilized as QCM surface coating layer. The performance of MIP films is characterized by 4-element QCM sensor array (three coated with MIP layers and one with pure PAA for reference) dynamic and static responses to target aldehydes: hexanal, heptanal, and nonanal in single, binary, and tertiary mixtures at distinct concentrations. The target aldehydes were selected subsequent to characterization of body odor samples with solid phase-micro extraction gas chromatography mass spectrometer (SPME-GC-MS). The hexanoic acid and octanoic acid imprinted PAA exhibit fast response, and better sensitivity, selectivity and reproducibility than the propenoic acid, and non-imprinted PAA in array. The response time and recovery time for hexanoic acid imprinted PAA are obtained as 5 s and 12 s respectively to typical concentrations of binary and tertiary mixtures of aldehydes using the static response. Dynamic sensor array response matrix has been processed with principal component analysis (PCA) for visual, and support vector machine (SVM) classifier for quantitative identification of target odors. Aldehyde odors were identified successfully in principal component (PC) space. SVM classifier results maximum recognition rate 79&#37; for three classes of binary odors and 83&#37; including single, binary, and tertiary odor classes in 3-fold cross validation.

DOI： 10.1016/j.talanta.2014.09.049

Language：English   Publishing type：Research paper (scientific journal)  

Synthesis and Self-Assembly of His-tag Hybrid of Substrate-Binging Short Domain in Transient Receptor Potential Vanilloid Type 1 for Vanillin Sensing Application
The amino acid sequence of vanillin-binding site of transient receptor potential vanilloid type 1 from rat, Leu⁵⁴⁴–Tyr⁵⁵³, was extracted and hybridized with His-tag. The hexadecamer invariant chain peptide, Leu-Ala-Met-Gly-Trp-Thr-Asn-Met-Leu-Tyr-His-His-His-His-His-His (VBH), was prepared by solid-phase peptide synthesis. Circular dichroic spectral measurements determined the α-helix content to be 17&#37;, which was consistent to that of short peptides. In a combined use of thiol-derivatized nitrilotriacetic acid (s-NTA) monolayers, the His-tag successfully attached the whole peptide on gold substrate surfaces through Ni²⁺-chelation (Γ_VBH = 224 ± 120 pmol cm^-2, n = 8). Moreover, various surface analyses including atomic force microscopy imaging, FT-IR spectroscopy, and quartz-crystal microgravimetry (QCM) revealed self-assembly (SA) of VBH at the S-NTA monolayer surfaces. QCM measurements also showed that vanillin, the major component of natural vanilla flavoring, binds to VBH SAs (K_app = 2.7 × 10³ M^–1). The affinity of host–guest binding remains limited but possesses a certain degree of selectivity; for cases of structural analogs that give a pleasant flavor, acetophenone showed rather weak affinity (K_app = 2.8 × 10² M^–1) whereas 4-heptanone did not bind at all. With these results VBH was concluded to be useful in vanillin sensing as a supramolecular affinity host.

DOI： 10.14723/tmrsj.40.175

Language：English   Publishing type：Research paper (scientific journal)  

Molecularly imprinted polymers (MIPs) have been prepared using the polyacrylic acid (PAA) as host polymer and hexanal, heptanal, and nonanal as pattern molecules. MIPs were employed as selective coating layer of quartz crystal microbalance (QCM) sensors. Hexanal, heptanal, and nonanal were opted as target chemicals after gas chromatography-mass spectrometer (GC-MS) characterization of body odor samples. Transient and static responses of four QCM sensors (three coated with MIPs and one with non-MIP) to target aldehydes in singly, binary and tertiary mixtures, and water at distinct concentrations have been measured. Transient responses were analyzed to compute the response time (ton), and recovery time (toff) of sensors. This result average values of ton ≤ 5 s and toff ≤ 10 s to typical concentrations of target odors. The sensitivity and baseline drift of sensors were also calculated using their static response. The heptanal template molecule based MIP coated QCM exhibit improved sensitivity, reproducibility and faster response, than the rest two MIPs, and non-MIP coated QCMs. Static sensors response matrices were further processed with principal component analysis (PCA) for qualitative (visual) discrimination and support vector machine (SVM) classifier for quantitative recognition (in &#37;) of target aldehydes: in singly, binary and tertiary mixtures. Aldehydes odor was effectively identified in principal component (PC) space. Maximum recognition rate of 89&#37; has been achieved for three classes of binary odors, and 79&#37; for the combination of single, binary and tertiary odor classes in 3-fold cross-validation of SVM classifier.

DOI： 10.1016/j.snb.2014.09.102

Language：Others  

In recent years, sensors for objective evaluation of quality and quantity of odor substances have shown a wide range of potential applications in many fields. However, the odor quality is difficult to be expressed by quantitative data because the odor sensation is brought about by a variety of volatile compounds, which form a complicated, subjective olfactory sense. Recent progress in molecular biological research of the olfactory system have shown that an odor cluster map produced on the surface of olfactory bulb through olfactory receptors presents essential information for brain to perceive odorants. The clustering perception model provides us with a new concept to design odor sensors with performance equivalent to mammalian olfactory system. The biological-inspired odor sensing based on various molecular recognition technologies, such as partial structure recognized water membrane/Pt electrodes, benzene-patterned self-assembled monolayer (SAM) layers, size and polarity selected molecular sieve materials, and molecularly imprinted polymer (MIP) adsorbents, are introduced to construct an artificial odor map and to evaluate the odor quality. On the other hand, odorants in our living environment can only be perceived by the sense of our olfactory, and odor space is invisible to eyes. The temporal and spatial distribution of odorants in environment is also important information for human and other animals. However, the visualization of odor space by using conventional sensor technologies is a difficult task due to the limited spatiotemporal resolution. Here optical sensing technologies based on fluorescence imaging and localized surface plasmon resonance (LSPR) are developed to visualize the spatiotemporal distribution of odorants in environment. In addition, the application of the developed sensors in the visualization of human body odor and odor release from fragrance encapsulated cyclodextrin inclusion complexes are presented also.

DOI： 10.1007/978-3-319-14711-6_9

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of Fluorescence-dyed Molecularly-Imprinted-Polymer Nanobeads for Odor Visualization
In this study, we reported an odor visualization system that can be used to visualize the spatial distribution of odors in environment. The sensing mechanism is based on the fluorescent intensity change caused by interactions between a fluorescent probe and odor molecules. A high sensitive CCD camera records the fluorescent quenching or enhancing and the odors are visualized by using an image processing software. In order to increase the sensitivity and selectivity of the visualization sensing film, novel fluorescent probes based on molecularly-imprinted-polymer (MIP) fluorescent nanobeads are developed and their visualization effects are introduced in this work.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of Molecular Imprinted Filtering Adsorbents for Odor Clustering
Sensors with the ability of qualitative and quantitative analysis for odors have not yet been applied. When odor signals perceived by olfactory receptors are transmitted to glomerulus, the latter will be activated by specific odor molecules to form an odor map. The activated glomerulus corresponding to odors with similar molecular profiles are located close sites on the olfactory bulb that consist of different clusters on the odor map. Therefore, the measurement and clustering of odor molecular profile (such as polarity and size) by artificial sensor will be a promising approach to evaluate odors similar to the human olfactory system. In this paper a bio-inspired odor adsorption-separation and sensing system is introduced for the qualitative measurement of odors. The selectivity of the sensor depends on adsorbent materials. So polymers with different SP parameters are chosen to adsorb various odor properties. Moreover, a novel molecular imprinted filtering adsorbent (MIFA) is developed to improve the recognition ability on odor molecules with different profiles. The combination with adsorbent layer and filter layer provides useful information for designing adsorbent materials with effective adsorption properties in connection with specific odor molecules.

Language：English  

In recent years, sensors for objective evaluation of quality and quantity of odor substances have shown a wide range of potential applications in many fields. However, the odor quality is difficult to be expressed by quantitative data because the odor sensation is brought about by a variety of volatile compounds, which form a complicated, subjective olfactory sense. Recent progress in molecular biological research of the olfactory system have shown that an odor cluster map produced on the surface of olfactory bulb through olfactory receptors presents essential information for brain to perceive odorants. The clustering perception model provides us with a new concept to design odor sensors with performance equivalent to mammalian olfactory system. The biological-inspired odor sensing based on various molecular recognition technologies, such as partial structure recognized water membrane/Pt electrodes, benzene-patterned self-assembled monolayer (SAM) layers, size and polarity selected molecular sieve materials, and molecularly imprinted polymer (MIP) adsorbents, are introduced to construct an artificial odor map and to evaluate the odor quality. On the other hand, odorants in our living environment can only be perceived by the sense of our olfactory, and odor space is invisible to eyes. The temporal and spatial distribution of odorants in environment is also important information for human and other animals. However, the visualization of odor space by using conventional sensor technologies is a difficult task due to the limited spatiotemporal resolution. Here optical sensing technologies based on fluorescence imaging and localized surface plasmon resonance (LSPR) are developed to visualize the spatiotemporal distribution of odorants in environment. In addition, the application of the developed sensors in the visualization of human body odor and odor release from fragrance encapsulated cyclodextrin inclusion complexes are presented also.

DOI： 10.1007/978-3-319-14711-6_9

Language：English  

The present study explores individual identity perception by analyzing the chemical peak information in the gas chromatography-mass spectrometry (GC-MS) spectra of body odor samples with standard data mining approaches. Mainly, the principal component analysis (PCA) method is chosen for the visual discrimination of the body odor samples in feature space. PCA in combination with the support vector machine (SVM) method is used for quantitative recognition. GC-MS characterization confirms the composition of numerous chemical species (aldehydes, acids, ketones, esters, sulfides etc.) in the body odor samples. The GC-MS spectra of body odor samples from the armpit and neck of three people (from dissimilar age groups) at two different sampling times (0 h and 4 h) were recorded in the experiment. A few blank (non-body odor) samples were also characterized with GC-MS and included as references in further analysis by the data mining methods. The discrimination efficiency (both qualitative and quantitative) for the individual body odors was evaluated for (i) three variables of chemical information in the GC-MS spectra (the peak area, peak height and ratio of peak area to height); (ii) two sampling times (0 h and 4 h); and (iii) two sampling parts of the body (the neck and armpit). The best visual discrimination of the individual body odors has been achieved using the peak height as a variable for the neck odor with a sampling time of 4 h. This result has been established with class separability measures calculated with principal component (PC) scores and SVM classification outcomes (86&#37;).

DOI： 10.1039/c5ay02457a

Language：English   Publishing type：Research paper (other academic)  

Functionalizing gold nanoparticles (AuNPs) for various applications, such as chemical sensors and catalysts, is widely studied in many fields. In this study, Functionalization of AuNPs by using dye materials was performed to provide the response ability to chemicals, based on the coupling interactions between AuNPs and dyes, such as quenching of fluorescence by metal existence or metal-enhanced fluorescence (MEF). While individual AuNPs or dyes do not indicate high response for most chemicals, the AuNP/dye complexes showed enhanced or novel chemical responses owing to the interactions between AuNPs and dyes. The response abilities of the complexes composed of AuNPs and several kinds of fluorescent dyes were studied, based on the changes of fluorescence intensity due to the presence of chemicals. The change of fluorescence spectra of the dye/AuNPs complexes in the presence of odor chemicals was investigated in order to develop odor imaging sensors with enhanced sensitivity and selectivity.

DOI： 10.1109/ICSENS.2014.6985158

Language：Japanese  

P-141 Development of odor sensing system using odor clustering based on molecular size

Language：English   Publishing type：Research paper (scientific journal)  

In present research, a novel volatile acids imprinted 3-element quartz crystal microbalance (QCM) sensor array has been designed for the selective recognition of organic acids odor. The target organic acids have been previously assigned as significant biomarker in human body odor and human waste odor. This is also confirmed with solid phase micro-extraction gas chromatography-mass spectrometer (SPME-GC-MS) characterization of body odor samples in present study. Polyacrylic acid (PAA) polymer has been used to prepare three selective molecular imprinted polymers (MIPs). MIP films were coated on the surface of QCM electrodes. Performance of MIP based QCM sensor array has been studied by exposing different concentrations of propenoic acid, hexanoic acid, and octanoic acid in singly and their binary mixtures. The response time and recovery time were 5 s and 14 s, respectively for one of the MIP coated QCM sensor to a typical binary mixture of acids odor. Frequency shift of QCM due to odor molecules adsorption in thin layer of MIP was measured as sensor signal. Sensor signal response matrix has been analyzed with principal component analysis (PCA) and support vector machine (SVM) methods for the odor recognition. The acid odors were identified effectively in principal component (PC) space. SVM classifier results 70-76&#37; recognition rate for three classes of binary odor. While excluding the binary mixture of propenoic acid and octanoic acid the average recognition rate approaches to 95&#37; in 3-fold cross validation of SVM classifier.

DOI： 10.1016/j.snb.2014.07.098

Language：English  

Language：Others   Publishing type：Research paper (scientific journal)  

Evaluation of odour release is important for the development of encapsulated fragrances. However, the use of existing instrumental analysis or gas-sensor technologies for odour-release evaluation is time- and labour-consuming. This paper introduces a fluorescence imaging system that can be used as a simple but effective tool to visualize the moisture-activated release of fragrance from cyclodextrin inclusion complexes. The visualization is based on the fluorescence changes of samples caused by the release of fragrance molecules from the cavity of cyclodextrin. Fluorescence spectroscopy investigations proved that different strategies could be used in the visualization depending on the molecular characters of the encapsulated fragrances. In the case of fragrance molecules with fluorescence (typically methyl anthranilate: MA), the change of fluorescence intensity was derived from the changed microenvironment of MA - from the encapsulated state to the released state. For the fragrance molecules without fluorescence (typically menthol), an appropriate fluorescent probe (7-amino-4-methylcoumarin: AMC) was used, and the fluorescence change was observed due to the interactions between AMC and the released menthol molecules. The real-time releases were visualized by two-dimensional/three-dimensional surface plots of the fluorescence images using image-processing software. Both the burst release occurring on the short time scale and the slow, natural release in ambient conditions can be demonstrated by the proposed visualization technique.

DOI： 10.1002/ffj.3213

Language：Japanese  

Language：Others   Publishing type：Research paper (scientific journal)  

A localized surface plasmon resonance sensor based on molecularly imprinted polymer (MIP) coated Au nanoparticle (AuNP) was developed to selectively detect α-pinene vapor. AuNPs were deposited on glass slides via Au ion sputtering method. The MIP was synthesized using methacrylic acid as monomer, ethylene glycol dimethylacrylate as cross-linker, and α-pinene as template. Adsorption characteristics of MIP powder and coating films were evaluated using gas chromatography mass spectrometry. The influence of molar ratio of template (α-pinene) to monomer on the absorption characteristics of MIP film was investigated. The largest affinity absorption amount of polymer film was achieved when the molar ratio of template to monomer was 1:4. Prepolymerized MIP mixture was spin coated on the sputtered AuNPs. The results showed that plasmon resonance peak in spectrum and the refractive index sensitivity depended on the polymer layer thickness. Better sensitivity and selectivity of MIP coated AuNPs sensor were realized at the spin coating speed about 1400 r/min. The real-time responses of α-pinene imprinted polymer coated AuNP sensor to three terpene vapors: α-pinene, limonene, and γ-terpinene were verified to be selective, rapid, and reversible. © 2001-2012 IEEE.

DOI： 10.1109/JSEN.2014.2346187

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.snb.2014.04.022

Language：Others   Publishing type：Research paper (scientific journal)  

Present study evaluates application of adaptive neuro-fuzzy inference system (ANFIS) for concentration estimation of volatile organic compounds (VOCs) by analyzing response matrix of polymer-functionalized surface acoustic wave (SAW) sensor array. The performance of ANFIS is compared with that of subtractive clustering based fuzzy inference system (SC-FIS) and backpropagation artificial neural network (BP-ANN). For analysis, the raw SAW sensor array data is preprocessed by logarithmic scaling followed by dimensional autoscaling and the feature extraction by principal component analysis (PCA). For concentration prediction, the extracted feature vectors were fed as input to the three methods (ANFIS, SC-FIS and BP-ANN) independently. The performance of the three methods were evaluated on the basis of root mean square error (RMSE) and correlation value involving actual and estimated values of concentration. Five sets of SAW sensor array responses are analyzed. The analysis includes both experimental and synthetic (sensor model generated) data sets. It is found that the ANFIS has the least value of RMSE and highest value of correlation compared to SC-FIS and BP-ANN. This signifies the relative superiority of ANFIS method. © 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.measurement.2014.05.002

Language：Others   Publishing type：Research paper (scientific journal)  

An advanced odor filtering and sensing system based on polymers, carbon molecular sieves, micro-ceramic heaters and metal oxide semiconductor (MOS) gas sensor array has been designed for quantitative identification of volatile organic chemicals (VOCs). MOS sensor resistance due to chemical vapor adsorption in filtering material and after desorption are measured for five target VOCs including acetone, benzene, ethanol, pentanal, and propenoic acid at distinct concentrations in between 3 and 500 parts per million (ppm). Two kinds of regression methods specifically linear regression analysis based on least square criterion and kernel function based support vector regression (SVR) have been employed to model sensor resistance with VOCs concentration. Scatter plot and Spearman's rank correlation coefficient (ρ) are used to investigate the strength of dependence of sensor resistance on vapor concentration and to search optimal filtering material for VOCs quantification prior to the regression analysis. Quantitative recognition efficiency of regression methods have been evaluated on the basis of coefficient of determination R2 (R-squared) and correlation values. MOS sensor resistance after vapor desorption with carbon molecular sieve (carboxen-1012) as filtering material results the maximum values of R-squared (R2 = 0.9957) and correlation (ρ = 1.00) between the actual and estimated concentration for propenoic acid using radial basis kernel based SVR method. © 2014 Elsevier B.V.

DOI： 10.1016/j.snb.2014.04.022

Language：English  

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Language：English  

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Language：English  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we examined the comprehensive detection of numerous volatile molecules based on the olfactory information constructed by using olfaction-inspired sensor technology. The sensor system can simultaneously detect multiple odors by the separation and condensation ability of molecularly imprinted filtering adsorbents (MIFAs), where a MIP filter with a molecular sieve was deposited on a polydimethylsiloxane (PDMS) substrate. The adsorption properties of MIFAs were evaluated using the solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The results demonstrated that the system embedded with MIFAs possesses high sensitivity and specific selectivity. The digitization and comprehensive classification of odors were accomplished by using artificial odor maps constructed through this system.

DOI： 10.3390/s140305221

Language：Japanese  

Language：English  

Language：Japanese  

Fabrication of Body Odor Sensing Device Based on Functional Gold Nanoparticles
Gold nanoparticles, which have various unique properties because of their smallness unlike bulky materials, are currently studied for the application to electronic devices, such as solar cells, sensors, and transistors. In our research, fabrication of the sensing devices based on the responsiviry of gold nanoparticles to the change of their environment was performed. The targets of sensing are volatile organic compounds, which causes odors. The research about the principles of nanogap formation of nanogap electrodes was also conducted, because the insufficient reproducibility of nanogap formation was the biggest obstacle in our study. At last, the scheme of further functionalization of these sensing devices is mentioned.

Language：Japanese  

Evaluation of deliciousness of tomato using taste, odor and visual information
Not only the five senses of taste, smell, sight, hearing and touch but also our physical and psychological conditions influence our judgment of the deliciousness of foods. Our research goal has been to develop a sensing system to express the deliciousness of foods by the fusion of sensors based on five senses of human. As the first step in this direction, we considered ways and means to the evaluations of deliciousness of tomato samples using the taste sensor, GC-MS and color measurements as taste, odor and visual information.

Language：Japanese  

Multispectral Imaging of Odor Space
Although the odor is invisibile, the odor have important informations as a danger signal. The odor information have the kind of odor material, density and spatial distribution, because the odor is vapor. In this study, with fluorescence probe as agarose gel film that mixed the fluorescence material, the odor information is extracted as fluorescence change. In this article, with multi fluorescence probe that mixed a number of fluorescence material, and with multispectral imaging, the discrimination of odor material is performed. This probe have ability that discriminates spatial distribution of odor density contained mixed odor, because the reaction of multi fluorescence probe is able to be divided the reaction of single fluorescence probe for each odor material.

Language：English   Publishing type：Research paper (other academic)  

This paper confirms the suitability of kernel principal component analysis (KPCA) as a robust feature extraction and denoising method in sensor array based vapor detection system (E-nose). Particularly the study focuses on response analysis of surface acoustic wave (SAW) sensor array in chemical class recognition of volatile organic compounds (VOCs). Usually KPCA results deprived performance compare to linear feature extraction methods. However its performance is affected by the proper selection of kernel function and optimization of allied parameters. We have presented the comparative performance analysis of feature vectors extracted by KPCA method using five types of kernel functions in combination with support vector machine (SVM) classifier. Study outcomes are based on analysis of 12 data sets (enclosing different intensity of additive noise and outliers) generated with SAW sensor model simulator. We find that in research of kernel function selection; polynomial kernel achieves persistently maximum class recognition rate of VOCs (average 82 %) even in presence of high level of additive Gaussian noise and outlier and anova kernel results minimum class recognition rate (average 70 %). The class recognition efficiency of feature vectors extracted by rest of the three kernel functions lies in between these two.

DOI： 10.1109/ISSNIP.2014.6827590

Language：English   Publishing type：Research paper (scientific journal)  

Objective of present study is to design an efficient odor sensor array based artificial electronic nose (E-nose) system for the detection of volatile organic compounds (VOCs) in medical and biometric applications. The E-nose system is designed with suitable unification of adsorbent materials, microceramic heaters, metal oxide semiconductor (MOX) gas sensors and pattern recognition unit. Polymers and carbon molecular sieves are used as adsorbent materials over the micro-ceramic heater to design an efficient odor filtering unit before analyte exposure to the sensor array. Sensor array response is measured for 75 different concentrations (in between 3-500 parts per million (ppm)) of five target VOCs including acetone, benzene, ethanol, pentanal, and propenoic acid. The influence of separating adsorbent material on sensor resistance is studied with objective to search the optimal material for VOCs filtering. Polydimethylsiloxane (PDMS) results highest sensitivity while carboxen- 1021 and carboxen-1012 result the lowest sensitivity as adsorbent materials for selected target VOCs. Sensor resistance (Ra) due to adsorption of VOCs by separating adsorbent material could be extracted from the sensor resistance (Rd) due to solvent desorption from the same. Fusion of these two sensor resistances is studied for data mining with objective to get improved class identification of target VOCs. Principal component analysis (PCA) as feature extraction method in combination with support vector machine (SVM) based classification is used to design pattern recognition unit for the class recognition of VOCs. Analysis results improved clustering of target VOCs in principal component (PC) space and average class recognition rate 82.66-100&#37; in 3-fold cross validation of SVM classifier.

DOI： 10.1166/sl.2014.3217

Language：English   Publishing type：Research paper (scientific journal)  

Odor sensors can benefit various areas of human activity and have been increasingly studied. For developing odor sensors, comprehensive detection of numerous volatile molecules is necessary. These advanced odor measurements might be accomplished by inspiring technology based on the bio-olfactory system. This system recognizes and discriminates odors by activity patterns, which are formed based on odor information of odorants extracted from olfactory receptors (ORs). Hence, odorants are appropriately categorized into clusters with different molecular features. The odor clustering close to biological olfaction can also be applied to the sensor systems. In this study, odor map images of rats investigated in biological studies were analyzed by principal component analysis (PCA) to clarify odor clustering features of olfaction. The definition of odor cluster and extraction of geometric features of odor maps were examined based on the primary components and factor loadings. Then, key parameters expressing clusters and measurable in sensor technology were successfully explored by evaluating the correlation between principal components and molecular parameters calculated using the molecular modeling software. Finally, artificial odor maps were reconstructed based on the defined odor clustering map, and the similarity between odor maps of rats was confirmed.

Language：English   Publishing type：Research paper (other academic)  

This study deals with data fusion approach to search discriminating biomarker volatile organic chemicals (VOCs) in body odor for individual differentiation. Particularly we have employed kernel principal component analysis (KPCA) combined with majority voting method to build up novel data fusion strategy. Gas chromatography-mass spectrometry (GC-MS) characterizes human body odor samples to find out the VOCs composition (alcohols, acids, aldehydes, esters, ketones, carbonyl compounds, sulfides and hydrocarbons etc.). Peak number and related area value of VOCs from the GC-MS spectra of body odor extract is used for analysis. GC-MS data from three experiments, based on body odor samples of four persons (different age groups) in dissimilar conditions are collected. Optimal set of peak numbers are selected with fusion approach. Linear PCA is used in validation of elected peak numbers for discrimination of individual's body odor. The opted peaks result satisfactory differentiation of individual's body odor in feature space. Thereafter biomarker VOCs are affirmed by matching corresponding peak number in GC-MS spectra. Analysis outcomes conclude particular set of biomarker VOCs for each experiment.

DOI： 10.1109/ISSNIP.2014.6827592

Language：English  

DOI： 10.1109/ICSENS.2013.6688508

Language：English   Publishing type：Research paper (other academic)  

Development of a sensor system with high molecular recognition ability was examined for comprehensive detection of numerous volatiles. The built system extracts molecular profiles and classifies odor and VOCs by structurally discernible adsorbents with high selectivity and condensation ability. These adsorbents have multilayer structures where molecular imprinted filter was fabricated on various concentrating materials. Target molecules were selectively absorbed into concentrating layers and other gases were blocked by the nanofiltration. Therefore, the system embedded developed adsorbents enables the detection and discrimination of low-concentrated gases. In addition, nano-filters are optimized and tailored for various applications. These possess not only the flexibility to be easily reconfigured with different properties, but also specific properties to interact with a variety of volatiles. In this study, basic characteristics of molecular filters with reconfigurability was investigated by applying functional materials.

DOI： 10.1109/ICSENS.2013.6688188

Language：Japanese  

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DOI： 10.1109/ICSENS.2013.6688152

Language：Japanese  

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Language：Others  

Chemical sensors that can be applied for an odor sensing must detect a very small portion of the bulk adsorbent. In order to realize this point it is necessary to observe an interaction between analytes and sensor surfaces sensitively. A candidate to achieve such chemical sensing is a switching behavior of a functional molecular that occurs on conductive molecules by adsorbing chemicals. If the electronic properties of the molecule are affected by such switching behavior, conductance will be easily changed. A charge transfer (CT) interaction between chemicals is a general concept for the conductance change, in which doping effect that causes donor or acceptor, Coulomb repulsion by electron correlation, or acid base reaction affects electrical conductance of materials. In the most typical case appeared in low dimensional conduct, CT interaction causes insulator-conductor transition, e.g., Mott transition, of materials, i.e., molecular switching phenomena. On the other hand, a nanostructured sensor surface is necessary to detect molecular conductance change caused by tiny analytes adsorption. In this study, we suggest sensor investigation for various volatile compounds by a transition of molecular wire conductance induced by electron-correlation interaction formation.

DOI： 10.4032/9789814303422

Language：Others   Publishing type：Research paper (scientific journal)  

Sensors that recognize molecules are acquired for the comprehensive detection of great many kinds of gases. Adsorbents with high molecular recognition and condensation ability were developed for selective gas sensing with a molecular imprinting technique. Developed adsorbents have multilayer structures consisted of a chemically modified polymer layer on the surface of a substrate covered by a TiO2 gel monolayer by the surface sol-gel process. Ellipsometry measurements showed that the 6-nm-thick layers deposited on the substrate. Cavities of molecular templates were imprinted on these layers, and thus, the film acts as a molecular gas filter without concentrating ability, which could form specific binding sites for various molecules that confirmed using solid-phase microextraction and gas chromatography-mass spectrometry. Gases were selectively absorbed into an accumulating adsorption layer and other gas molecules were blocked by the nanofiltration. These developed adsorbents enabled effective concentration ability and the filtration of gases or odors. In addition, these filters possess the flexibility to be easily configured with specific surface properties to interact with volatile molecules under appropriate conditions. A successful multiplex filter, imprinted simultaneously on an adsorbent with different sites, was demonstrated. © 2013 Elsevier Inc.

DOI： 10.1016/j.jcis.2013.05.051

Language：Japanese  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Odor Image Sensing by Multi Probe Film
In recent years, a way to objective evaluation of the quality and quantity of the odor is required to resolve issues such as odor nuisance, gas explosions and poisoning gas detections. It is also required to detect and track their harmful odors, and remove their sources radically. In this study, we tried to measure odor substances by fluorescent quenching. We developed imaging film to realize optical odor sensing using fluorescence dyes and the odor gas detection system using the film and a cooled CCD camera. The system could detect gaseous odor flow and visualize shape, spread and concentration distribution of odor. In addition, we developed a multi-film and FRET probes for high sensitive and selective detection of odor. FRET probe consisted of a certain combination of fluorescence dyes such as tryptophan and vanillin. FRET probe could detect odors that could not be detected by a single fluorescence probe. Multi probe film consisted of e.g. tryptophan and quinine sulfate. Multiple information of odors could be acquired by catching image of the multi probe film with interference filters.

DOI： 10.1541/ieejsmas.133.199

Language：English  

Language：Japanese  

Development of a sensing film for odor clustering
When human receive the odor molecules, appropriate glomerulus that corresponds to the specific molecular profile are activated Glomerulus corresponding to similar molecular profile is located closely at the site on the olfactory bulb and forms a cluster In the sense of smell, there are no basic odors, however the olfactory cluster can be considered as basic information about odor quality In this research, we fabricated the Au nanoparticles(AuNPs) substrate modified with polyacrylic acid(PAA) and molecular imprinted polymers (MIP) layer This film examines the properties of sample gas from differences in combination properties of sample gas of three types For the LSPR(localized surface plasmon resonance) phenomenon of AuNPs, we can consider the colorimetric method using CCD camera By the selectivity of MIP layer , the sensing film exposure to different gas can obtain different patterns of image with the process of subtract computing between ongin image and resultant image These images implicitly show the similarity or difference of the type of odor Therefore, clustering of odor can be realized by imaging method.

Language：Japanese  

Odor Detection by Fluorescent His-TRPV1
In recent years, a way to objective evaluation of the quality and quantity of the odor is required to resolve issues such as odor nuisance, gas explosions and poisoning gas It is also required to detect and track their harmful odors, and remove their sources radically In other words, imaging odors is required In a previous study, we succeeded in visualizing the odor by combining high-sensitivity CCD camera and a fluorescence dye However, there is a problem that selectivity of fluorescent probe is not high So we have designed a oligo-peptide based on a biological vanilloid receptor that interacts specifically to a particular odorant In this study, we have evaluated specificity of the peptide for vanillin using a fluorescence spectrophotometer and the QCM sensor As a result, We were able to confirm the significance of the peptide for vanillm With these results further applications can be expected in the visualization of odors.

Language：English  

Quantitative and qualitative measurements of odor are indispensable for the development of odor display systems that can reproduce odor at any place in any time. This chapter covers odor evaluation techniques based on human senses, instrumental analyses, odor sensors, and data analysis methods dedicated to odor measuring techniques. The chapter consists of the four following sections: sensory evaluation, gas analysis instruments, odor sensing system, and pattern analysis for odor sensing system. The first section describes odor evaluation methods with human senses. The second section gives an overview of instrumental laboratory techniques for olfaction research. The third section surveys sensor devices for odor detection. Finally, the last section gives the basic statistical methods and advanced pattern analysis for odor sensing systems.

DOI： 10.4018/978-1-4666-2521-1.ch005

Language：English  

In biological olfactory systems, odor receptors receive odor molecules by recognizing the molecular information. Humans can sense the odor by the signal from these activated receptors. The combination of the activated receptors is called "odor code," and the odor codes are expressed as an "odor cluster map" of glomeruli on the olfactory bulb surface. The odor code is essential information for qualitative and quantitative analyses of odor sensation. In this chapter, development of odor sensors based on the odor code concept and an attempt to extract the parameters for odor coding from molecular informatics are described. Application of the obtained odor code for odor reproduction is also presented.

DOI： 10.4018/978-1-4666-2521-1.ch024

Language：English  

Language：English   Publishing type：Research paper (other academic)  

Au nanoparticles (Au NPs) multilayer structures have been fabricated by an alternate deposition of a bifunctional dithiol cross-linker and Au NPs, to analyze the localized surface plasmon resonance spectra and the refractive index sensitivity to terpene vapors. UV-vis spectroscopy and atomic force microscopy (AFM) have been used to characterize the obtained multilayer structures. The investigations show that the number of Au NPs deposition cycles has effects on the multilayer structure fabrication and the refractive index sensitivity of the sensor.

DOI： 10.1109/ICSENS.2012.6411152

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

The sensing of carbon monoxide (CO) impurity contained in hydrogen fuel is a challenging work in the field of low temperature proton exchange membrane fuel cell (PEMFC). In the present work a chemiresistive gas sensor based on polyaniline (PANI) nanofibers was developed to detect CO in hydrogen. The sensor was fabricated by a template-free electrochemical polymerization of aniline on an interdigitated electrode. The most distinctive feature of the fabricated sensor was the formation of a horizontally oriented, monolayered PANI nanofiber network on the insulating gap area. The gas sensing character of the PANI nanosensor was evaluated by measuring the change in electrical resistance when gas atmosphere was changed from pure hydrogen to mixtures of CO in hydrogen. The results demonstrated that the PANI nanosensor had an excellent responding ability on CO in hydrogen with a concentration as low as 1 ppm. The influences of parameters, such as nanostructure, doping level, dopants, and CO concentrations, on the sensing characters of the nanosensor were discussed. The responding mechanism was attributed to the different binding sites of CO and H₂ with PANI: H₂ with the protonated amine nitrogen atoms and CO with the unprotonated amine nitrogen atoms. In view of its novel sensing mechanism and high sensing performance, the fabricated sensor is very promising to be applied as a new type of CO sensor to prevent the catalysis poisoning of PEMFC. Highlights: A chemiresistive polyaniline nanofiber sensor is developed to detect CO in hydrogen. The nanofiber sensor is fabricated by a template-free electrochemical polymerization. The nanofibers have a horizontally oriented, monolayered network structure. The sensor shows a reversible, rapid response on 1 ppm CO in hydrogen. The sensor can be used to prevent the CO poisoning of catalyst in PEM fuel cell.

DOI： 10.1016/j.ijhydene.2012.06.096

DOI： 10.5162

Language：English  

DOI： 10.5162

Language：Japanese  

Odor clustering using odor molecular sieving adsorbents

Language：Japanese  

Odor Imaging by Fluorescent Probe

Language：English  

In this study, odor evaluation and discrimination are examined. First, an odor separating system that imitates the odor receptive mechanism of biological olfaction is developed. This system enables a rough detection of odor by measuring the molecular size and polarity of odorants. Using representative odor materials that belong to different biological glomeruli clusters, odor information extracted on time course patterns can be obtained by the system. The extracted features can be used for creating an odor map similar to the one created in the receptive mechanism, which can classify qualities by their odor-cluster attributes. Mixed odors can be discriminated and decomposed into their elemental clusters. The map obtained from this study can be used for odor matching analysis.

DOI： 10.1016/j.snb.2012.03.041

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Odor gas detection is important for the detection of explosives, environmental sensing, biometrics, foodstuffs and a comfortable life. Such odor-source localizations is an active research area for robotics. In this study, we tried to detect odor chemicals with an optical method that can be applied for the spatiotemporal detection of odor. We used four types of fluorescence dyes; tryptophan, quinine sulfate, acridine orange, and 1-anilinonaphthalene-8-sulfonate (ANS). As analyses, we measured the following four odor chemicals, 2-furaldehyde, vanillin, acetophenone, and benzaldehyde. The fluorescence-quenching mechanism of PET (Photoinduced Electron Transfer) or FRET (Fluorescence Resonance Electron Transfer), which occur between fluorescence dyes and odor compounds, could prevent unintended detection of various odorants that is caused by their unspecific adsorption onto the detecting materials. The fluorescence changes were then observed. Thus, we could detect the odor substances through fluorescent quenching by using the fluorescence dyes. Odor information could be obtained by response patterns across all the fluorescence dyes. Moreover, we captured odor images with a cooled CCD camera. Shapes of the targets that emitted odor could be roughly recognized by the odor-shape images. From the spatiotemporal images of odors, twodimensional odor expanse could be obtained.

DOI： 10.20965/jrm.2012.p0047

Language：English   Publishing type：Research paper (scientific journal)  

A chemiresistive sensor based on polyaniline (PANI) nanofibers decorated with highly dispersed gold nanoparticles (AuNPs) is developed to detect the volatile sulfur compounds (VSCs) of human expired breath. The PANI nanofibers with a characteristic of horizontal orientation on the insulating gap area of an interdigitated electrode are prepared by a temple-free electrochemical polymerization. The formation of the fine AuNPs on the PANI nanofibers is realized by the redox reaction between HAuCl ₄ and PANI in the form of emeraldine. The PANI/AuNPs sensors exhibit good sensing responses to H ₂S and CH ₃SH gases. The sensing ability of the fabricated electrodes on VSCs contained in human breath is confirmed by their response upon exposure to the expired breath of a healthy volunteer after ingesting raw garlic. The developed nanosensors, together with a multichannel sensing system, are expected to be used in breath analysis and disease diagnose related to malodor biomarker gases.

DOI： 10.1016/j.snb.2011.10.068

Language：Japanese  

Gas sensing with Local plasmon resonance
Robots equipped with gas sensors have already been studied and applied for detecting the gas distribution or determining the gas source. Because the purpose of this kind of robots is to recognize the environment condition while their moving, a fast and compact gas sensing device is required. However, the response time of the conventional gas sensors are too long for the robot application. For example, the response time of semiconductor gas sensor is in a few minutes. Based on this fact, we focused on the localized plasmon phenomenon of noble metal nanoparticles (NPs), and developed a gas sensor which responses within a second. In this report, aims to increase the sensitivity of NPs, (1) the relationship between the preparation condition and the optical properties of NPs, (2) the difference between AuNPs and AgNPs, (3) the effect of thermal annealing treatment, (4) the effect of Au colloid surface modification are examined. As a result, fast response of all NPs, the large sensitivity of non annealed AgNPs, and the sharp resonance of annealed NPs are obtained.

Language：Japanese  

Development of odor sensing film for odor imaging sensor
In recent years, a way to objective evaluation of the quality and quantity of the odor is required to resolve issues such as odor nuisance, gas explosions and poisoning gas. It is also required to detect and track their-harmful odors, and remove their sources radically. In this study, we tried to measure odor materials by fluorescent quenching. Furthermore, we developed odor sensing film using fluorescence dyes and the odor gas detection system using the film and CCD camera. The system could detect gas odor and visualize shape, spread and concentration distribution of odor.

Language：English   Publishing type：Research paper (other academic)  

In this study, we developed novel adsorbents materials with high selectivity and condensation ability for embedding in the sensor technology. These adsorbents, called molecularly imprinted polymer adsorbents (MIPAs), become sandwich structures where a molecular imprinted polymer (MIP) nano-filter was fabricated with a specific binding site for a variety of odorants on the surface of a polydimethylsiloxane (PDMS) substrate as adsorbents. Because molecules with similar molecular structure can pass through the MIP filter, the MIPAs exhibit high molecular sieve effect. The selectivity of MIPAs was evaluated by using the solid-phase microextraction (SPME)-GC/MS method. The embedded MIPA properties were also confirmed measured using the sensor system.

DOI： 10.1109/ICSENS.2012.6411156

Language：English   Publishing type：Research paper (other academic)  

In this research, achievement of the odor discrimination was examined. At first, odor separating system was developed which imitates the odor receptive mechanism of biological olfaction. A rough detection of odor becomes possible with this device. Therefore, this device makes it possible to measure the molecular size and the polarity of odorant and discriminate the mixed odor. Then, measuring representative odor molecules belonging to biological glomeruli clusters, odor information is extracted from time course patterns obtained by the system. The extracted features could be used for odor mapping close to the odor map created in the odor receptive mechanism which can classify odor quality by their odor cluster attributes.

DOI： 10.1063/1.3626294

Language：English   Publishing type：Research paper (other academic)  

We have been focusing on sebum for discriminating human body odor. In this study, we examined body odor sampled from 12 male examinees. Through the experiment, we detected statistically-significant differences between 56 pairs of examinees out of 66 pairs (approximately 85%). This result shows that our system and principle enabled discrimination of body odor between examinees to a certain extent.

DOI： 10.1063/1.3626366

Language：English  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (international conference proceedings)  

We have been focusing on sebum for discriminating human body odor. In this study, we examined body odor sampled from 12 male examinees. Through the experiment, we detected statistically-significant differences between 56 pairs of examinees out of 66 pairs (approximately 85&#37;). This result shows that our system and principle enabled discrimination of body odor between examinees to a certain extent. © 2011 American Institute of Physics.

DOI： 10.1063/1.3626294

Language：English   Publishing type：Research paper (international conference proceedings)  

In this research, achievement of the odor discrimination was examined. At first, odor separating system was developed which imitates the odor receptive mechanism of biological olfaction. A rough detection of odor becomes possible with this device. Therefore, this device makes it possible to measure the molecular size and the polarity of odorant and discriminate the mixed odor. Then, measuring representative odor molecules belonging to biological glomeruli clusters, odor information is extracted from time course patterns obtained by the system. The extracted features could be used for odor mapping close to the odor map created in the odor receptive mechanism which can classify odor quality by their odor cluster attributes. © 2011 American Institute of Physics.

DOI： 10.1063/1.3626294

Language：Japanese  

Language：Japanese  

Pattern recognition of body odor by molecular sieve effect of zeolite

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

We report fabrication of an odor sensor using peptides. Peptides were designed to acquire the specific reception for a target odor molecule. Au surface of the sensor electrode was coated by the designed peptide using the method of self assembled monolayers (SAMs). Functionalized Au surfaces by the peptides were confirmed by ellipsometry and cyclic voltammetry. The odorants of vanillin, phenethyl alcohol and hexanol were discriminated by QCM sensor with the peptide surface. Moreover, we verified specific interaction between amino acid (Trp) and vanillin by fluorescence assay.

DOI： 10.1541/ieejsmas.130.282

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

In order to obtain practicable nano-conducting polymer resistive sensors, we investigated the electrochemical deposition of polyaniline (PANI) on the insulating gap area of an interdigitated electrode with a gap width as great as 100 μm. We revealed that the nucleation and growth of PANI on the insulating substrate were influenced by the surface character of the substrate such as hydrophilicity and roughness. By controlling the polymerization conditions, homogeneous PANI films with various nanostructures could be obtained across the insulating gap to form resistive junctions. Among them, a loose 2D nanowire network structure showed the best sensing performance upon exposure to ammonia gas with a low concentration.

DOI： 10.1016/j.elecom.2009.10.030

Language：English   Publishing type：Research paper (other academic)  

By directly chemical oxidative polymerization of aniline on Au electrode treated with Au nanoparticles (Au- NPs) deposition and 4-aminothiophenol (ATP) modification, polyaniline (PANI) fibers were obtained in-situ in micro- /nano- size with two dimensional network structures. It was found that the ATP modification played an important role for the formation of fibrous network and in the decrease in the contact resistance between the PANI film and the electrode surface. The PANI film showed a rapid response upon the exposure to various gases with low detection limit, which indicated that the developed PANI sensor could be applied in the high sensitive detection of hazardous gases

DOI： 10.1063/1.3156547

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

In biological systems, odor receptors receive odor molecules by recognizing molecular information. Recent studies have shown that the size and electrical dipole of molecules are important for odor reception. We developed an odor code sensor that recognizes essential molecular information for reconstructing the odor code of odor molecules. The substructure of odor molecules is a candidate target property of a developed odor code sensor. The substructures of odorants are received at the sensor surface; therefore, the design of surface functionality is important. In this study, a self- assembled monolayer (SAM) was used to construct a nanospace that fits the substructure of odor molecules. A surface that can recognize substructures was fabricated by the mixed SAM method. A competitive method and a replacement method were examined for SAM surface preparation. The mixed SAMs obtained were analyzed by contact angle measurement, ellipsometry, and an electrochemical method. Finally, the surface was evaluated through odorant responses, and the specificity to odorants was confirmed.

Language：English   Publishing type：Research paper (scientific journal)  

By a chemical oxidative polymerization of aniline on solid substrates treated with Au nanoparticles (Au-NPs) deposition and 4-aminothiophenol (ATP) modification, polyaniline (PANI) fibers were obtained in micro-/nanosize with two-dimensional network structures. The observation by laser scanning microscopy (LSM) indicated that the formation of PANI fibrous network occurred during the drying process rather than the polymerization. It was suggested the ATP modification on Au-NPs deposited substrate resulted in an inhomogeneous grafting of solution-formed PANI on the solid substrates, which self-aggregated to the fibrous network structure with the evaporation of water due to interchain interactions. The influence of polymerization conditions on the formation of fibrous network and the conducting property of the prepared film were discussed. Results from the gas sensing of the as-prepared PANI sensor upon exposure to NH₃ confirmed that the sensitivity and responding rapidity was improved greatly by the PANI 2D fibrous network structure. Especially, a rapid response in resistance change on NH₃ with low concentration indicated that the developed method in this work can be used to fabricate highly sensitive PANI gas sensors.

DOI： 10.1016/j.synthmet.2009.01.029

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Attention has been focused recently on the harmful effects and malodor of sulfuric compounds; therefore, various laws have been enacted to regulate environmental concentration and use of most sulfuric compounds. In order to avoid sulfuric malodor, a reasonable, easy, sensitive, and selective measuring method to detect sulfuric compounds is required. In this research, we adopted the specific adsorption of sulfuric compounds to a metal surface as a sensing principle. It was suggested that polarization is an important factor of molecular recognition from results obtained by quartz crystal microbalance (QCM), ellipsometry, and stripping voltammetry (SV). Therefore, we used cyclic surface polarization impedance (cSPI), based on electrochemical impedance spectroscopy (EIS) under the dynamic control of an electrode potential and a constant phase element (CPE) impedance, as a detecting method for sulfuric compounds. As a result, we could detect three sulfuric compounds, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, with this method at sub ppb levels and discriminate the three sulfuric compounds. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.20420

Language：English   Publishing type：Research paper (other academic)  

By directly chemical oxidative polymerization of aniline on Au electrode treated with Au nanoparticles (Au- NPs) deposition and 4-aminothiophenol (ATP) modification, polyaniline (PANI) fibers were obtained in-situ in micro- /nano- size with two dimensional network structures. It was found that the ATP modification played an important role for the formation of fibrous network and in the decrease in the contact resistance between the PANI film and the electrode surface. The PANI film showed a rapid response upon the exposure to various gases with low detection limit, which indicated that the developed PANI sensor could be applied in the high sensitive detection of hazardous gases © 2009 American Institute of Physics.

DOI： 10.1063/1.3156547

Language：English   Publishing type：Research paper (scientific journal)  

In biological systems, odor receptors receive odor molecules by recognizing molecular information. Recent studies have shown that the size and electrical dipole of molecules are important for odor reception. We developed an odor code sensor that recognizes essential molecular information for reconstructing the odor code of odor molecules. The substructure of odor molecules is a candidate target property of a developed odor code sensor. The substructures of odorants are received at the sensor surface; therefore, the design of surface functionality is important. In this study, a self- assembled monolayer (SAM) was used to construct a nanospace that fits the substructure of odor molecules. A surface that can recognize substructures was fabricated by the mixed SAM method. A competitive method and a replacement method were examined for SAM surface preparation. The mixed SAMs obtained were analyzed by contact angle measurement, ellipsometry, and an electrochemical method. Finally, the surface was evaluated through odorant responses, and the specificity to odorants was confirmed.

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Attention has been focused recently on the harmful effects and malodor of sulfuric compounds; therefore, various laws have been enacted to regulate environmental concentration and use of most sulfuric compounds. In order to avoid sulfuric malodor, a reasonable, easy, sensitive, and selective measuring method to detect sulfuric compounds is required. In this research, we adopted the specific adsorption of sulfuric compounds to a metal surface as a sensing principle. It was suggested that polarization is an important factor of molecular recognition from results obtained by quartz crystal microbalance (QCM), ellipsometry, and stripping voltammetry (SV). Therefore, we used cyclic surface polarization impedance (cSPI), based on electrochemical impedance spectroscopy (EIS) under the dynamic control of an electrode potential and a constant phase element (CPE) impedance, as a detecting method for sulfuric compounds. As a result, we could detect three sulfuric compounds, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, with this method at sub ppb levels and discriminate the three sulfuric compounds.

DOI： 10.1002/tee.20420

Language：English   Publishing type：Research paper (scientific journal)  

A taste sensor chip miniaturized on the basis of the one-chip-size receptor part of a conventional taste sensor, which can measure taste using lipid/polymer membranes, was fabricated. The reference electrode in the taste sensor chip realized the miniaturization and stabilization of potential using a multilayer structure of a pHEMA layer and other polymer layers. In this study, we improved the stability of the taste sensor chip during the measurement by changing the material of the partition of the taste sensor chip to plastic. We successfully integrated the working and reference electrodes on the chip. The portable taste sensor system was composed of the taste sensor chip, an integrated electric signal processing part and a laptop computer. We considered that the design of the portable taste sensor facilitates the easy manual measurement of taste. By realizing the taste sensor chip and the portable taste sensor, taste measurement can be easily performed anywhere.

Language：English  

Development of Odor Code Sensor Recognizing Substructure of Odor Molecules

Language：English   Publishing type：Research paper (scientific journal)  

A taste sensor chip miniaturized on the basis of the one-chip-size receptor part of a conventional taste sensor, which can measure taste using lipid/polymer membranes, was fabricated. The reference electrode in the taste sensor chip realized the miniaturization and stabilization of potential using a multilayer structure of a pHEMA layer and other polymer layers. In this study, we improved the stability of the taste sensor chip during the measurement by changing the material of the partition of the taste sensor chip to plastic. We successfully integrated the working and reference electrodes on the chip. The portable taste sensor system was composed of the taste sensor chip, an integrated electric signal processing part and a laptop computer. We considered that the design of the portable taste sensor facilitates the easy manual measurement of taste. By realizing the taste sensor chip and the portable taste sensor, taste measurement can be easily performed anywhere.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

A biological olfaction system is one of the highest performance chemical sensing systems for low-molecular-weight compounds. An ability of recognizing a various molecular properties based on their structures is essential for a biological odor recognition process. For the development of a sensor mimicking the olfactory system, we have formed benzene-patterned self-assembled monolayer (SAM) on the sensor surface using SAMs with nanostructure that serves as adsorption sites for benzene ring, which is representative substructure of aromatics. The structure of the benzene-patterned SAM surface was analyzed by contact-angle measurement, ellipsometry, cyclic voltammetry (CV) and atomic force microscopy (AFM). Moreover, the electrodes evaluated as sensor surfaces with cyclic surface-polarization impedance (cSPI) sensor that measures changes in impedance of the electrode surface by adsorption of substances. The results of cSPI indicated the benzene-patterned SAM surface could distinguish benzene by recognizing of the hydrophobicity and the molecular size.

DOI： 10.1016/j.snb.2007.08.027

Language：English  

Odor is a one of important sensing parameters for human life. However, odor has not been quantified by a measuring instrument because of its vagueness. In this paper, a measuring of odor with odor coding, which are vector quantities of plural odor molecular information, and its applications are described.

DOI： 10.1541/ieejsmas.128.29

Language：English  

Language：Japanese  

The detection of specified offensive odor substances by electrochemical method
Attention has been recently focused on the harmful effects of malodor; hence, various laws regulate the use of malodor materials. Therefore, a reasonable, easy, sensitive and selective measuring method to detect malodor materials is required. In this research, we used a specific adsorption of malodor molecules to a metal surface; i.e. Au-S bond and AgO-R-COOH bond. We found that a polarization is the most important factor of a molecular recognition. So we use cSPI as the method of detecting malodor materials. cSPI is one of the electrochemical method that enables EIS (electric impedance spectroscopy) measurement, a dynamic control of an electrode potential and CPE (constant phase element) impedance measurement reflecting an inhomogeneous surface at the level of an atom. We detected sulfur compounds and organic acids in this method. In the case of organic acids an oxidation effect with TiO_2 was also adopted for the detecting method. As a result, we could detect up to regulated level and discriminate malodor materials correctly. Using this method, we may detect the other malodor materials.

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Recently, the electrical characteristics of metal-molecule-metal nanowires are studied. Interaction between the junction molecule and the analytes will affect the molecular orbital that alters a conductive path. We have been interested in charge transfer (CT) interaction that induces the partial transfer of electron from an electron donor to an electron acceptor. The measurement result obtained with crossed-wire tunneling junction indicated that the CT interaction provides a significant conductance change of the junction molecule. In this report, we suggest a nanowire sensor to detect volatile organic compounds (VOC) by conductance switching brought on by the charge transfer interaction. The sensor surface possesses a molecular wire network formed by bridging nanogaps between Au nanoparticles (Au-NPs) with electron donor molecules. The Au-NPs were fabricated by sputter deposition with controlling the particle-size and the gap-size. We confirmed the donor oligothiophene bridging by resistance transition and the formation of CT interaction between oligothiophene and analytes by fluorescence quenching. The conductance of the sensor electrode increased by adsorption of electron acceptors, such as iodine and aromatic nitro compounds.

DOI： 10.1109/ICSENS.2007.4388478

Language：Japanese  

Mobile robot with early fire detection system using odor sensor array

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

High-sensitive detection of sulfur compounds by Electrochemical Impedance Spectroscopy

Language：English   Publishing type：Research paper (scientific journal)  

Highly sensitive and selective detection of 2,4-DNT, a representative explosive, was achieved by the synergic effect of molecular imprinting and host (cyclodextrin)-guest interaction in ultrathin layers of TiO₂ and SiO₂ gel; the detection limit using cSPI measurements reached nM concentration.

DOI： 10.1039/b703132g

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

The quantification of the senses requires the interpretation of a biological recognition process. In olfactory senses, the receptors on the olfactory epithelium receive odor molecules by recognizing not their whole rigid chemical structures but their common properties. In this study, we attempted to develop an artificial olfactory epithelium system that can recognize the molecular information of odor. This system was constructed using an electrochemical cell and has been developed by the functionalization of sensor channels with the composition of electrolyte solution and with surface modification technologies. As a result, the odor information of aromatic alcohols could be represented, depending on molecular substructures.

Language：English   Publishing type：Research paper (scientific journal)  

In order to achieve high sensitive and selective detection for nitro aromatic compounds related with landmines, γ-cyclodextrin (γ-CD) hosts were introduced onto the TiO₂ ultrathin layer. The surface of the Pt electrode was modified with ultrathin TiO₂ gel film immobilized with γ-CD molecular hosts through the surface sol-gel process. The surface modification of the electrode was confirmed by QCM (9 MHz) and X-ray photoelectron spectra (XPS) experiments. As a result, an alternate assembly film of Ti(O-ⁿBu)₄ and γ-CD prepared on the gold coated QCM as a substrate showed linearly growth, and judging from the large carbon and oxygen ratios of XPS spectra in the TiO₂/γCD film of the Pt electrode surface, it was confirmed that γ-CD hosts must be adsorbed onto the TiO₂ ultrathin layers. Furthermore, the resulting γ-CD-immobilized TiO₂/γ-CD ultrathin films for the high sensitive detection of nitro aromatic compounds were examined by cyclic surface-polarization impedance (cSPI) spectroscopy which is a newly developed chemical sensor measuring electrochemical impedance change due to constant phase element (CPE) behavior on the electrode surface under controlled electrode potential. Consequently the resulting TiO₂/γ-CD films showed specific and sensitive detection for 2,4-dinitrotoluene (2,4-DNT) among the examined guest molecules. Moreover, a high impedance response value for 2,4-DNT compared to structurally related other molecules was achieved by the specific host-guest interaction, estimated to be 1.6-3.4 times larger at the concentration of 2 × 10^-8 M.

DOI： 10.1016/j.snb.2006.08.035

Language：Japanese  

Language：Japanese  

The detection of volatile organic substances using conductive nanostructural surface

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Electron acceptor molecules form charge transfer (CT) complexes with electron donors. CT complexes are known as an organic conductive material. In this report, we suggest a nanowire sensor to detect electron-acceptive aromatic nitro compounds by conductance switching brought on by charge transfer interaction. The sensor surface possesses a molecular wire network formed by bridging nanogaps between Au nanoparticles (Au-NPs) with electron donor oligothiophene. The Au-NPs were fabricated by sputter deposition with controlling the particle-size and the gap-size. We confirmed the oligothiophene bridging by resistivity and the formation of CT interaction between oligothiophene and electron acceptors by fluorescence quenching. The conductance of the sensor electrode was increased by adsorption of electron acceptors, such as iodine and aromatic nitro compounds.

DOI： 10.1109/SENSOR.2007.4300408

Language：Japanese  

Odor measurement using artificial olfactory epithelium

Language：English   Publishing type：Research paper (scientific journal)  

Nitro-aromatic compounds could be sensitively detected by employing cyclic voltammetric experiments in ultrathin TiO₂ gel/cyclodextrin (CD) multilayered films that were prepared via the gas-phase surface sol-gel process. Among others, 2,4-DNT showed the highest voltammetric response for the γ-CD immobilized TiO₂ film and its detection limit was estimated to be less than nM levels.

DOI： 10.1246/cl.2006.1340

Language：Japanese  

Language：Japanese  

Odor coding and synthesis based on molecular informatics

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we report the sensitive detection of aromatic nitro compounds using a surface plasmon resonance (SPR) immunosensor based on the indirect competitive method. The vapors from the substances were sampled with a preconcentrator developed here. The solutions of the sampled vapors were measured using SPR immunosensor. Three kinds of explosives such as 2,4-dinitrobenzene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene were detected at 1 ppb. Sampling time at 11/min was 3 min. Total detection time was brought down to 5 min, which is relatively short for second scanning in landmine detection. Efforts are being made to integrate the SPR immunosensor and preconcentrator for rapid sensitive detection of nitro aromatic compounds under simulated field conditions.

DOI： 10.1541/ieejsmas.126.621

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we report the sensitive detection of aromatic nitro compounds using a surface plasmon resonance (SPR) immunosensor based on the indirect competitive method. The vapors from the substances were sampled with a preconcentrator developed here. The solutions of the sampled vapors were measured using SPR immunosensor. Three kinds of explosives such as 2,4-dinitrobenzene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene were detected at 1 ppb. Sampling time at 11/min was 3 min. Total detection time was brought down to 5 min, which is relatively short for second scanning in landmine detection. Efforts are being made to integrate the SPR immunosensor and preconcentrator for rapid sensitive detection of nitro aromatic compounds under simulated field conditions.

DOI： 10.1541/ieejsmas.126.621

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A highly effective approach was developed for sensitive detection of organic substances in water. In order to achieve high sensitivity and selective detection for aromatic compounds, cyclodextTim (CD) hosts and imprinting effects were combined to fabricate binding sites within TiO2 UltTathin layer. The electrode surface was modified with ultrathin TiO2 gel film containing a 2:1 complex of beta-CD and bisphenol A (BPA), and then the BPA moiety was removed by washing. The resulting BPA-imprinted TiO2/beta-CD film showed specific and sensitive detection of BPA, as confirmed by quartz crystal microbalance (QCM) and cyclic surface-polarization impedance (cSPI) measurements. The high selectivity for BPA relative to structurally related guest molecules was estimated to be 1.6-3.4 at the guest concentration of 2 x 10(-7) M, and was considered to arise from the synergic effect of the binding site. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bios.2006.06.013

Language：Others  

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Attention has been recently focused on the harmful effects of aldehydes; hence, various laws regulate the use of most aldehydes. Therefore, a quick, easy, and continuously operating method of detecting aldehydes is required. In this study, we utilized the silver mirror reaction known as a specific reaction of aldehydes to detect aldehydes selectively. We performed the silver mirror reaction on a working electrode surface, and the reaction products which were deposited on the surface were measured by voltammetry. As a result, we could develop a simple measuring method of detecting aldehydes quickly that could distinguish aldehydes from ketones. In addition, we configured the measurement conditions to make the continuous measurement of aldehydes possible. We brought together the reaction field and electrolysis cell, optimized the supporting electrolyte and the mixing ratio of diamine silver ions of ammoniacal silver nitride solution, and improved the controlling sequence of the voltage applied to the working electrode. Consequently, we could continuously measure the level of aldehydes.

Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper reports miniaturization on one-chip size of a receptor part of taste sensor, which can measure the taste using lipid/polymer membranes. The miniaturization was made by producing metal electrodes and making lipid/polymer membranes deposit on a glass substrate. The reference electrode also realized a miniaturization and stabilization of potential according to laminating structures of pHEMA and polymer layers. Therefore, an integration of the working and the reference electrodes was attained on the chip. By realization of this taste sensor chip, taste measurement can be easily performed now in all places, such as the distribution industry and the medicine manufacture industry, including the food industry. Moreover, we succeeded to fabricate the portable taste sensor system which unified the amplifier, a data-processing unit and an LCD display. © 2006 IEEE.

DOI： 10.1109/MMB.2006.251522

Language：Japanese  

Language：English  

Language：Japanese  

Development of sensor surface recognizing substructure
Recently, odor sensor recognizing substructures of odor molecules, which imitates the biological odor recognition process, has been developed. In the development of such odor sensor, we have formed the adsorption site for aromatic ring, included in many odor molecules, on the sensor surface using self-assembled monolayer (SAM), in order to detect peculiar substructures with high specificity. In addition, the surface structure of such sensor surface was analysed by contact-angle measurement and cyclic voltammetry. Moreover, the change in the reactance of cyclic surface-polarization impedance (SPI) led by the adsorption of substaces indicated such sensor surface could detect benzene with high specificity.

Language：English   Publishing type：Research paper (other academic)  

This paper reports miniaturization on one-chip size of a receptor part of taste sensor, which can measure the taste using lipid/polymer membranes. The miniaturization was made by producing metal electrodes and making lipid/polymer membranes deposit on a glass substrate. The reference electrode also realized a miniaturization and stabilization of potential according to laminating structures of pHEMA and polymer layers. Therefore, an integration of the working and the reference electrodes was attained on the chip. By realization of this taste sensor chip, taste measurement can be easily performed now in all places, such as the distribution industry and the medicine manufacture industry, including the food industry. Moreover, we succeeded to fabricate the portable taste sensor system which unified the amplifier, a data-processing unit and an LCD display.

DOI： 10.1109/MMB.2006.251522

Language：English   Publishing type：Research paper (other academic)  

In order to imitate the mechanism of biological odor reception, an integrated multi-channel odor sensor was developed here. In this study, we attempted to control the response characteristics of this odor sensor by the composition of the water membrane and surface modification technology. As a result, the addition of P cellulose, ion-exchange resin, to the water membrane enabled large response to ethanol, which has hydroxyl group in its structure, and the formation of benzene-patterned self-assembled monolayer (SAM) enhanced the sensitivity to benzene, which has aromatic ring in its structure. In addition, both technologies were also appropriate for the detection of phenethyl alcohol, which has both hydroxyl group and aromatic ring; consequently, these channels could recognize the molecular substructures.

DOI： 10.1109/SENSOR.2005.1497464

Language：English  

Language：Japanese  

Development of Integrated Odor Sensor
In biological systems, odor molecules are dissolved into nasal mucus, and are received by odor receptors on olfactory epithelium through recognizing molecular structures. In this study, we have paid attention to the fact that the biological odor-reception process contributes to the odor quality; therefore, integrated odor sensor was developed in order to materialize the artificial olfactory epithelium. As a result, odor molecules are trapped by a water membrane corresponded to the nasal mucus, and we can recognize the molecular substructures of the odor molecules by surface-polarization controlling method. In addition, the sensor surfaces, which responded to the particular molecular substructures, were created by the composition of the water membrane or surface modification. Thus, it became possible to evaluate the odor qualitatively and quantitatively.

Language：English   Publishing type：Research paper (international conference proceedings)  

In order to imitate the mechanism of biological odor reception, an integrated multi-channel odor sensor was developed here. In this study, we attempted to control the response characteristics of this odor sensor by the composition of the water membrane and surface modification technology. As a result, the addition of P cellulose, ion-exchange resin, to the water membrane enabled large response to ethanol, which has hydroxyl group in its structure, and the formation of benzene-patterned self-assembled monolayer (SAM) enhanced the sensitivity to benzene, which has aromatic ring in its structure. In addition, both technologies were also appropriate for the detection of phenethyl alcohol, which has both hydroxyl group and aromatic ring; consequently, these channels could recognize the molecular substructures. © 2005 IEEE.

DOI： 10.1109/SENSOR.2005.1497464

Language：Japanese  

Development of the high-sensitive and selective detection method for aldehydes

Language：English   Publishing type：Research paper (international conference proceedings)  

The global demands for landmine abolition become stronger, whereas the development of landmine detection technology progresses slowly. At present, the detection activities are mainly performed by means of a metal detector or a well-trained dog that needs much time and cost. Therefore, a more efficient landmine detection technique is desired. Most landmines contain aromatic nitro compounds, such as 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) as explosive charges; therefore, these substances are clues for landmines. In this study, we tried to detect amount of aromatic nitro compounds high-sensitively using a surface-polarization controlling method that measures electrochemical impedance of an electrode surface where explosive compounds adsorbed. As a result, we could detect the aromatic nitro compounds at detection limits of sub-μM level and distinguish the aromatic nitro compounds from other aromatic compounds at 100 μM at least. Furthermore, in order to improve specificity and sensitivity to aromatic nitro compounds, the electrode surface was modified with arenes that makes charge-transfer complex with aromatic nitro compounds. We adopted anthracene as the arene to functionalize the electrode surface. The modified electrode makes it possible to detect the aromatic nitro compounds selectively. This method enables us to develop a sensor for landmine detection. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2004.12.102

Language：English   Publishing type：Research paper (scientific journal)  

Aldehyde and carboxylic acid compounds are known as volatile substances with bad smell. It is also said to cause bad smell of tap water. In this study, we tried to detect and analyse aldehyde and carboxylic acid dissolved in water, using a surface-polarity controlled sensor. The sensor measures electrochemical impedance of the electrode surface whose electric potential is dynamically controlled. Adsorption and desorption of target chemicals cause changes in impedance which has constant phase element (CPE) characteristics. The impedance changes depending on the electrode potential are used as a chemical sensor output. As a result, we could detect and distinguish many kinds of aldehyde and carboxylic acids. Furthermore various water pollutant can be detected with high sensitivity. The results suggest that a simple and multi-purposed sensor can be constructed for environmental analysis using the proposed method.

DOI： 10.1541/ieejsmas.125.75

Language：English   Publishing type：Research paper (other academic)  

A new electrochemical sensor with high sensitivity and selectivity for heavy-metal ions was proposed. The sensor was based on the electrochemical impedance spectroscopy (EIS) attributing to a constant phase element (CPE) behavior under dynamically controlled electrode potential. With the measurements of the CPE behavior by the surface-polarization controlling method, various heavy-metal ions could be easily detected and discriminated. No interference of counter anions such as Cl^-, NO₃^- and CH ₃COO^- was observed, and the same metal ions gave similar sensor response patterns regardless of the counter anions. Especially, the present method offers a high sensitivity of ppb levels for the most highly toxic elements, i.e., Hg²⁺ and Hg⁺.

Language：English   Publishing type：Research paper (other academic)  

A sensitive landmine detection method with easy operation is demanded, however, sensors satisfied both sensitivity and ease have not been developed yet. The purpose of this study is to develop the high-sensitive chemical sensor that can easily and quickly identify the explosive molecules leaking from landmines. It is conceivable that such technology could be applied to a sensor for security. In this paper, we describe a sensor using a surface polarization controlling method. We improved specificity and sensitivity to aromatic nitro compounds by introducing the modified electrode with Lewis base that has the charge-transfer interaction with aromatic nitro compounds. Furthermore, the modified electrode could be characterized with fluorescence spectroscopy.

DOI： 10.1109/SENSOR.2005.1497473

Language：English   Publishing type：Research paper (other academic)  

Chemical sensor which can be used for a multi-purpose chemical measurement to detect various chemical substances with a small number of a sensor array was investigated. It was confirmed that chemical compounds adsorbed strongly and irreversibly on a platinum surface using conventional electrochemical methods and an instrumental surface analysis. The adsorbates were also analyzed by means of an electrochemical impedance spectroscopy under dynamic potential scan; measured impedance reflects CPE (constant phase element) properties of the electrode surface. The method provides a convenient technique for the surface analysis of adsorbing chemicals. The CPE response profile was modified through chemical adsorption/desorption and the interaction between the polarized surface and chemical substances. Consequently, various profiles depending on chemical substances were obtained and it had quantitative and qualitative information about chemicals interacting with the surface. The present method which does not require a specific electrochemical reaction can be applied.for multi-purpose chemical sensors and also simple chemical analyses.

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A novel odor sensing system which imitates the process of reception of odorants in biological olfactory system had been developed, utilizing surface polarity controlling method as a transducer of the sensor. In biological system, odorants are received by a large number of receptors, which recognize not whole structures but partial structures of molecules. The present sensor responded partial structures of odorants and adsorption interaction of the partial structures were controlled by the surface polarity of the electrode. Sensor output signals were analyzed on the stand point of partial structures of odorants. As a result, the responses to alcohols, aromatic compounds and aromatic alcohols as odorants could be discriminated by similar molecular structures, with principal component analysis (PCA). In addition, regression models of the response to partial structures of odorants were developed by multiple regression analysis, and odor qualities of aromatic alcohols could be evaluated quantitatively by partial structures of odor molecules. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2003.11.030

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

In order to improve the sensitivity of the surface-polarization controlling method to detect aromatic compounds which are hazardous chemicals, self-assembled monolayers (SAMs) in benzene were evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. A cyclic voltammogram for the reductive desorption of SAMs adsorbed from a benzene solution containing 1-octanethiol (OT) suggested that OT adsorbed on Au surfaces competed with bulk benzene molecules. The results of electrochemical impedance spectroscopy also revealed the structure of SAMs with benzene holes. Furthermore, benzene can be specifically identified at less than 1 ppm using the benzene-patterned SAM.

Language：English   Publishing type：Research paper (scientific journal)  

Monosodium glutamate (MSG) induces a favorable taste, termed umami. The action of MSG on lipid membranes of a taste sensor was investigated. In general, food constituents monotonously increase the electric potential of the negatively charged membranes. Contrary to this, MSG decreases the potential at lower concentration and increases it at higher concentration, thus the effect of MSG on lipid membrane is biphasic. On the decrease of the membrane potential, a model was proposed in which the dissociated carboxyl group of MSG accelerates the dissociation of phosphate group of the membrane lipid. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-4005(03)00087-X

Language：English   Publishing type：Research paper (scientific journal)  

Taste qualities were studied using a method for detecting the change in interactions between an electrode surface and taste substances in aqueous solution. The present method to detect chemicals was categorized into impedance spectroscopy in electrochemistry. Taste substances affect the electrochemical impedance by adsorption to the electrode surface. Dependences of the impedance on the electrode potential showed different patterns for five basic taste substances with different taste qualities. Furthermore, the response profiles obtained for capsaicin, piperine and allyl isothiocyanate, which are natural pungent-taste substances and have strong hydrophobic groups, were discriminated from those for bitter taste substances using a new method detecting the change of electrode impedance by addition of the mediators of chemical interactions to the taste substances. Hydrophobic substances, which were difficult to discriminate using the electrochemical method, could be discriminated by a proposed method; hence, it was possible to detect wide range of chemical substances from hydrophilic electrolytes to various hydrophobic non-electrolytes. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-4005(02)00457-4

Language：English  

Language：Japanese  

Quantification of pungent-tasting strength using surface-polarity controlled sensor

Language：Japanese  

High Sensitive Detection of Plant State Changes using Chloroplast Fluorescence

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A flow cell incorporating a liquid junction was fabricated for sequential analysis using the surface-polarity-controlled sensor. In the present flow cell, a porous wall or an S-shaped route acts as a liquid junction to prevent contamination of the reference-electrode solution. The stability of the electric potential of the Ag/AgCl reference electrode in these flow-cell systems was studied, and both of the liquid junctions were highly effective in keeping the electrode potential stable. In the surface-polarity-control method, good agreement of sensor response was confirmed between the batch system and the flow-cell system with the S-shaped junction, although large resistance of the porous wall junction influenced the estimation of the impedance of the working electrode/solution interface. A portable and general-purpose chemical sensor can possibly be realized using the surface-polarity-controlled sensor with a flow-cell system which utilizes flow injection analysis.

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

An electronic tongue based on voltammetry and a multichannel lipid membrane taste sensor based on potentiometry are compared using two aqueous examples: detergents and teas. The electronic tongue consists of four electrodes of different metals, a reference electrode and a counter electrode. The measurement principle is based on pulse voltammetry in which current is measured during the change of the amplitude of the applied potential. The taste sensor is based on eight different lipid/polymer membranes. The voltage difference between the electrodes and an Ag/AgCl reference electrode is measured when the current is close to zero. The responses from the two sensors systems are treated separately with multivariate data analysis based on principal component analysis and then merged to examine if further information could be extracted. It is shown that although the two sensor systems are about equal in separation ability in the two cases, extra information can be gained by combination of the two sensor systems.

DOI： 10.1016/S0003-2670(01)01349-6

Language：English   Publishing type：Research paper (scientific journal)  

Electric potential changes of optically active membranes due to different amino acid isomers were measured using a multichannel lipid membrane sensor. Because of the diastereomeric interaction between amino acids and the membrane, the membrane potential was determined by the optical activity of both the amino acid and the membrane. Diastereomeric interactions occur when an enantiomeric membrane resides in a chiral environment. The homochiral and heterochiral diastereomeric interactions differ sufficiently in the resultant arrangement of molecules at the surface of the membrane and permit the discrimination of D-amino acids from L-amino acids due to changes in the membrane characteristics.

Language：English   Publishing type：Research paper (scientific journal)  

In order to analyze the taste quality of amino acids, basic taste substances were studied using the surface-polarity controlled sensor. The sensor outputs showed different potential profile patterns for basic taste substances that have different taste qualities, while it showed similar patterns for amino acids which have similar taste. However, all amino acids used in the analysis had a basic peak around 0.1 V due to a basic amino group (NH2) in the amino acid molecules. Therefore, in order to compare the taste quality of amino acids with that of basic taste substances, a basic peak around 0.1 V of amino acids was eliminated by a curve fitting analysis. With the result, the taste quality of amino acids could be classified into four groups according to that of basic taste substances.

Language：English   Publishing type：Research paper (scientific journal)  

In order to analyze the taste quality of amino acids, basic taste substances were studied using the surface-polarity controlled sensor. The sensor outputs showed different potential profile patterns for basic taste substances that have different taste qualities, while it showed similar patterns for amino acids which have similar taste. However, all amino acids used in the analysis had a basic peak around 0.1 V due to a basic amino group (NH₂) in the amino acid molecules. Therefore, in order to compare the taste quality of amino acids with that of basic taste substances, a basic peak around 0.1 V of amino acids was eliminated by a curve fitting analysis. With the result, the taste quality of amino acids could be classified into four groups according to that of basic taste substances.

Language：English  

Chemical sensor using polarity controlled fractal surface

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The tastes of amino acids were studied using a method for detecting the change in the interaction between an electrode surface and amino acids in aqueous solution. The electrode impedance showed different patterns of potential profiles for amino acids with different taste qualities, while it showed similar patterns for amino acids with similar tastes. Amino acids may be classified into four groups according to their tastes based on sensor outputs. The sensor response correlated well with human sensitivities and showed higher sensitivity than human sensation. This method can provide useful transducers for the development of sensors to analyze taste qualitatively and quantitatively.

Language：English   Publishing type：Research paper (scientific journal)  

It has been noticed recently that there is a possibility of elution of chemical substances from packages of foods. The chemicals act as harmful substances such as environmental hormones for biological bodies at very low concentration. It is therefore necessary to develop a sensing device, which can detect such substances easily and quickly. The purpose of the present study is high sensitive measurement of environmental hormones using electrode polarity controlling method. The responding ability of the polarity-controlled sensor covers various chemicals from electrolytes to nonelectrolytes and from hydrophilic to hydrophobic substances. As a result, we could sensitively detect bisphenol-A at about 50 ppb and dibutyl phthalate at about 3 ppb, and the sensor could distinguish such chemicals from ordinary taste substances.

DOI： 10.1541/ieejsmas.121.215

Language：English  

Language：Japanese  

Characterization of metal electrode surface and responses to chemical substances

Language：Japanese  

Detection of odor substances by controlling surface polarity of electrode

Language：English   Publishing type：Research paper (scientific journal)  

SUMMARY There are methods used to test the optical purity of enantiomers; however, most of the simple methods are not precise and more complicated methods are better. As a result, these methods cannot be widely used for industrial purposes. The aim of this research is to design a sensor which can discriminate D-amino acids from L-amino acids. The designed sensor has chiral membranes and uses the technique of impedance change of these chiral membranes to discriminate the amino acids. Ve used a noisc-FFT (Fast Fourier Transform) technique to determine the membrane impedance. When an enantiomer membrane resides in a chiral environment, (E), diastereomeric interactions (E*-D) and (E*-L) are created, which may differ sufficiently in the arrangement of molecules of the membranes so as to permit the discrimination of optical substances due to the change in membrane characteristics. With increasing concentrations of the amino acids, the membrane resistance changes depended on the optical activity of the amino acids. The results suggest that the impedance changes of the chiral membrane with diastereomeric reaction can be used for the high-performance chemical sensor to measure the optical purity of different substances.

Language：English  

Detection of environmental hormones with electrode polarity controlled method

Language：Japanese  

Sensing of chemical substances through modulation of surface polarization

Language：English   Publishing type：Research paper (scientific journal)  

The effect of basic taste substances on lipids is investigated by mixing lipids, lecithin and DPPC (dipalmitoyl phosphatidylcholine), with five basic taste substance solutions at different concentrations and measuring their near infrared radiation (NIR) absorbance. On adding a taste solution to lecithin, second derivatives of the original curves revealed that certain peaks were slightly shifted. Out of the five taste substances (quinine, sucrose, NaCl, HCl and MSG) used, only sucrose maintained the transition temperature of hydrated DPPC.

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

The present study investigates adsorption of taste substances to lipid membranes for the multichannel taste sensor. To clarify the mechanism of adsorption of taste substances to a lipid membrane, we measured adsorption quantities of taste substances, such as amino acids and quinine-HCl, with fluorometry, and the surface of the lipid membrane was analyzed with ESCA (Electron spectroscopy for chemical analysis). Furthermore, we measured potential responses of a lipid membrane and pH of monosodium glutamate and lipid solutions. The results showed that amino acids adsorb to the lipid membrane, but no specific adsorption site exists on the membrane. The adsorption occurred by weak interaction between a phosphoric acid group of lipid molecules and an amino group of amino acids. Quinine-HCl adsorbed to membrane with strong electrostatic coupling and weak hydrophobic effects to lipid molecules in the membrane.

DOI： 10.1541/ieejsmas.119.374

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Photovoltaic effects of semiconductor were examined for chemical sensing. Light induced potential change influences surface electrical polarity through lighy generated carriers, then characteristics of electrode changes and the electrode respond to various chemicals. Odor and taste substances have various electrical property and affect the light induced potential change. We can detect very sensitively electrolyte or nonelectrolyte, such as sucrose, ethanol and mono sodium glutamate by changes of photo voltage. The results suggest that characteristics of the transducer can be controlled and information of chemicals multiplexed in a signal from a single transducer.

DOI： 10.1541/ieejsmas.117.95

Language：Japanese  

Measurement of adsorption of taste substances to lipid membrane for taste senser

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Lipid membranes are useful materials to transform information about taste substances into electric signals. A lipid monolayer membrane for a taste sensor has been prepared by adsorbing lipid materials to the hydrophobic surface of a polymer membrane. The lipid-modified membranes respond to such electrolytic taste substances as HCl (sourness) or NaCl (saltiness) with large response magnitudes and such non-electrolytic substances as caffeine (bitterness) or sugar (sweetness) with high sensitivities. Thus the present membrane has a high ability to detect taste. © 1995, All rights reserved.

DOI： 10.1016/0925-4005(94)01522-J

Language：English  

Sensing of Chemical Substances Using Light Induced Potential Changes of Organic Membranes

Language：English  

Chemical Sensing and Response Ability Control Using Photovoltaic Effect of Semiconductor

Language：English   Publishing type：Research paper (scientific journal)  

A taste sensor with a multichannel electrode was developed by using lipid membranes as a transducer of taste substances. The sensor can detect the taste in a similar manner to the human gustatory sensation by response patterns of electric potential to taste substances. The sensitivity, reproducibility and durability were superior to those of humans. The same taste as that elicited by some commercial aqueous drink was reproduced by making aqueous solution mixed from four kinds of basic taste substances, the concentrations of which were determined so that the electric-potential pattern of this mixed solution could agree well with the pattern by the drink. Different brands of beer were easily distinguished by the electric-potential patterns.

DOI： 10.1016/0956-5663(94)80036-7

Language：Others   Publishing type：Research paper (scientific journal)  

Lipid-membrane materials are effective as a transducer of taste sensors. The Langmuir-Blodgett (LB) film was investigated as a candidate of transducer materials. The membrane potential responded to taste substances showing sourness, saltiness and umami with high sensitivity, but scarcely responded to sweet and bitter substances.

DOI： 10.9746/sicetr1965.29.1012

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Stable electrochemical patterns appear spontaneously around roots of higher plants and are closely related to growth. An electric potential pattern accompanied by lateral root emergence was measured along the surface of the primary root of adzuki bean (Phaseolus angularis) over 21 h using a microelectrode manipulated by a newly developed apparatus. The electric potential became lower at the point where a lateral root emerged. This change preceded the emergence of the lateral root by about 10 h. A theory is presented for calculating two-dimensional patterns of electric potential and electric current density around the primary root (and a lateral root) using only data on the one-dimensional electric potential measured near the surface of the primary root. The development of the lateral root inside the primary root is associated with the influx of electric current of about 0.7 μA · cm^-2 at the surface.

DOI： 10.1104/pp.100.2.614

Language：English   Publishing type：Research paper (scientific journal)  

It is known that thiol-containing compounds form monolayer membranes on a gold surface via chemisorption from organic solvents in terms of a strong connection ability between thiol and the metal. Here we prepared different kinds of thiol-containing lipids and fabricated monolayer membranes on the gold disk electrode whose surface structures were similar to biological membranes. Responses of this lipid-coated electrode to odor substances were examined by an electrochemical method of a cyclic voltammetry. Blocking ability for the redox reaction of Fe(CN)63− was found to change upon adsorption of odor substances into monolayer membranes. The order of threshold values to detect the odorants was β-iononeβ-citralβchloroform≦n-amyl acetate; this order was the same as that in the human olfactory sense. The present study indicates that the monolayer membrane of thiol-containing lipids can be useful as a transducer of an odor sensor. © 1992 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.31.1555

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

An apparatus for measuring simultaneously the surface electrical potentials along epicotyl was developed to study the largely bending situation by gravity. Potentials increased on the upper side and decreased on the lower side after the horizontal placement. The time course of electrical changes consisted of two components which correspond to growth movements observed during gravitropism.

DOI： 10.1104/pp.97.1.193

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Extracellular and intracellular electric potentials in bean roots are known to show electric oscillations along the longitudinal axis with a period of several minutes. The relationship between growth and the electric oscillations was studied using roots of adzuki (Phaseolus chrysanthos). We measured surface electric potentials with a multielectrode apparatus while simultaneously measuring elongation using a CCD camera and monitor. Roots having an electric oscillation grew faster than roots with no oscillation. Furthermore, elongation rate was higher in roots with higher oscillation frequency. Oscillation frequency had a strong dependence on temperature; i.e. Q₁₀ was estimated at 1.7. These results suggest a correlation between electric oscillation and elongation.

DOI： 10.1104/pp.93.2.532

Language：Others   Publishing type：Research paper (scientific journal)  

We have developed a taste sensor consisting of a multichannel electrode with transducers composed of lipid membranes immobilized with a polymer, i.e., eight different kinds of lipid analogs mixed with poly(vinyl chloride) and plasticizer. This multichannel sensor responds to five basic taste substances in five different ways; the taste patterns composed of eight electric-potential responses could be clearly distinguished from each other for the five basic taste substances. Moreover, similar but distinguishable patterns were obtained for substances eliciting a similar taste in humans. The reproducibility is noticeably improved from those of lipid membranes which were previously investigated for application in a taste sensor. The present results imply that the multichannel lipid membrane device has the ability to sense tastes like a human being. © 1990.

DOI： 10.1016/0925-4005(90)85006-K

Language：English   Publishing type：Research paper (scientific journal)  

A spatial pattern of electric potential in the growing root was studied with a usual microelectrode and a multi-electrode measuring apparatus, which made possible a simultaneous measurement of electric potentials along the root. The pattern of surface electric potential disappeared along the entire root length when air surrounding the plant was replaced with nitrogen gas for about 2 h. Disappearance of a large peak of surface potential around 10 mm from the root tip preceded both the decrease in the growth speed and the change in pH of the aqueous medium to neutral in the elongation region, while this region showed a localized acidification in normal conditions. Supply of air recovered the spatial patterns of electric potential and pH. Proton accumulation within the cell wall following activation of H⁺ pumps was suggested to participate directly in the growth.

DOI： 10.1143/JPSJ.59.370

Language：English   Publishing type：Research paper (scientific journal)  

A correlation dimension and a distribution pattern of spectrum intensities of a self-sustained electric oscillation were studied for an aperiodic oscillation induced by an application of electric current on a membrane of a synthetic lipid, dioleyl phosphate. The estimated dimension showed a remarkable deviation in the presence of taste substances such as quinine (above a certain threshold value) from that in the absence of these taste substances; this deviation was accompanied by a change in spectrum pattern. The present result indicates that the two variables extracted from the aperiodic oscillations will be useful as sensing information in a chemical taste sensor using lipid membranes.

DOI： 10.1143/JJAP.28.1507

Language：English   Publishing type：Research paper (scientific journal)  

Sweet substances (sucrose, lactose, glucose, fructose, galactose, glycerin and aspartame), excepting Na saccharin, effectively interacted with a negatively-charged lipid membrane of dioleyl phosphate (DOPH). These sweet substances decreased the membrane resistance and depolarized the membrane potential. This response differed from those to bitter, sour and salty substances. Together with the result for transient response, it is suggested that sweet substances could penetrate the lipid membrane. Mono- and disaccharides exerted their effects at a concentration corresponding to the threshold value of taste sensation in vivo. Aspartame, which is about 100-fold sweeter than sucrose, was effective at one-hundredth of this concentration. In addition, the effect of sweet substances on a positively-charged lipid membrane was studied. Changes in the membrane electrical potential and resistance were observed by employing Na saccharin, which had no effect on the DOPH membrane.

DOI： 10.1271/bbb1961.53.675

Language：English   Publishing type：Research paper (scientific journal)  

A theory is presented for a relationship between ion accumulation and electric current loops in multicellular systems such as the roots and stems of higher plants. A network of electric circuits shows that the electric current transported across the cell membrane flows between an elongating region and a mature region, not only in roots but also in stems. In roots, ions constituting the extracellular electric current flow in the external aqueous medium, while in stems an electric current of comparable density flows within the epidermal cell wall. Based on this theoretical result, electric isolation between the elongating and mature regions was made in the case of both roots and stems. The speed of growth during the initial stage was greatly decreased due to a change in the distribution of protons around the surfaces of the plant by cutting off the electric current loop. Electrochemical calculation shows that ions are not always accumulated at the efflux site, since the ion distribution is strongly affected by the relation of the magnitudes between the electric field and electric current. The results calculated for the electric potential and pH distributions around the root agree with experimental data.

DOI： 10.1016/0301-4622(89)80019-5

Language：English   Publishing type：Research paper (scientific journal)  

The effect of taste substances was investigated for a lipid membrane constructed by casting complexes of synthetic lipid (double-chain ammonium salt) and sodium polystyrenesulfonate on a silicon wafer with a single minute pore. Reproducibility of the electric properties was improved remarkably by the use of the present construction method for the lipid membrane. It was found that this membrane showed a sensitive response to negatively-charged chemicals having strong bitterness such as picric acid because the lipids are positively charged. A membrane with non-equimolar lipid-polymer complexes showed a phase separation between two phases composed of liquid-crystal lipid multi-bilayers and crystal lipid-polymers within a limited temperature range. This membrane in the phase-separation state generated a self-sustained electric oscillation, whose mechanism was explained with the aid of a non-equilibrium theory. The waveform of the oscillation changed by using picric acid on the membrane. This bio-mimetic membrane has the possibility of acting as a biological chemoreceptor.

DOI： 10.1016/0250-6874(89)80003-4

Language：English   Publishing type：Research paper (scientific journal)  

Sweet substances (sucrose, lactose, glucose, fructose, galactose, glycerin and aspartame), excepting Na saccharin, effectively interacted with a negatively-charged lipid membrane of dioleyl phosphate (DOPH). These sweet substances decreased the membrane resistance and depolarized the membrane potential. This response differed from those to bitter, sour and salty substances. Together with the result for transient response, it is suggested that sweet substances could penetrate the lipid membrane. Mono- and disaccharides exerted their effects at a concentration corresponding to the threshold value of taste sensation in vivo. Aspartame, which is about 100-fold sweeter than sucrose, was effective at one-hundredth of this concentration. In addition, the effect of sweet substances on a positively-charged lipid membrane was studied. Changes in the membrane electrical potential and resistance were observed by employing Na saccharin, which had no effect on the DOPH membrane.

DOI： 10.1080/00021369.1989.10869372

Language：English   Publishing type：Research paper (scientific journal)  

Electric spatial patterns of bands formed along the cell wall of the characean internode were studied using a multi-electrode measuring system. The electric potential near the surface of the cell was measured by arranging about 25 electrodes along the cell at approximately 1.6 mm intervals. Since the time required for one scan over the cell length is only 1 s, the temporal change in the spatial pattern of surface electric potential can be readily observed. Oscillations were sometimes found as the electric pattern started to appear after the cell was illuminated. Fourier analysis shows that a single spatial mode arises gradually and then becomes stabilized in an oscillatory manner. A simple electric circuit model comprising three variables, i.e., a membrane potential, an electric current across the membrane and an electromotive force, can simulate well the oscillatory rise of bands. These results imply that the electric spatial pattern observed in characean internodes is a self-organized structure emerging far from equilibrium, known as a dissipative structure. Biophysical mechanisms of band formation are discussed.

DOI： 10.1007/BF00255321

Language：English   Publishing type：Research paper (scientific journal)  

Spatial patterns of surface electric potential of a root of azuki bean (Phaseolus chrysanthos) were investigated. A multi-electrode measuring system was used to measure the spatial pattern and its variation with time. It was found that a periodic pattern was spontaneously formed along the root but it disappeared under anoxia. Supply of air made the pattern recover. Although the change in electric potential started from the root tip under anoxia, it occurred first near the seed in the recovery process when air was supplied. To explain this phenomenon, a simplified theoretical model was proposed. The model is described by a differential equation for a concentration of oxygen expressing longitudinal diffusion and consumption of oxygen within the root. Assumption of a threshold of the oxygen concentration needed to activate a respiration-dependent pump led to a quantitative explanation of the above behaviour of surface electric potential. It was suggested that the pattern belongs to a group of self-organized dynamic structures which are maintained through energy metabolism by a supply of material from outside.

DOI： 10.1093/oxfordjournals.aob.a087685

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1143/JPSJ.57.2864

Language：Japanese  

Language：Others   Publishing type：Research paper (scientific journal)  

A spatial pattern of the electric potential formed by a characean internodal cell is investigated experimentally. A multi-electrode measuring system is used to pursue the dynamic properties of the pattern. It is shown that periodic low-potential regions are formed after the entire transient increase over the cell when the light is imposed on. Under constant illumination an electric oscillation is found. These experimental data are also discussed by the use of a spectrum analysis; the formation of the pattern is a bifurcation phenomenon of soft-mode instability realizing far from equilibrium, accompanied by sharpening of spectrum of a particular wave mode. A long-range coherence extending over 1 cm is also shown to exist in the high-potential region, where protons are extruded by H+-ATPase molecules existing within the membrane. © 1987, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

DOI： 10.1143/JPSJ.56.810

Language：English   Publishing type：Research paper (scientific journal)  

The electric spatial pattern and invertase activity distribution in growing roots of azuki bean (Phaseolus chrysanthos) have been studied. The electric potential near the surface along the root showed a banding pattern with a spatial period of about 2 cm. It was found that the enzyme activity has a peak around 3-7 mm from the root tip, in good agreement with the position of the first peak of the electric potential, which is located a little behind the elongation zone. An inhomogeneous distribution of ATP content was also detected along the root. Experiments on the electric isolation of the elongation zone from the mature zone and acidification treatment showed that H⁺ is transported from the mature-side to elongation-side regions, causing tip elongation through an acid-growth mechanism. Both acidification and electric disturbance on growing roots affected growth significantly. Simultaneous measurements of electric potential and enzyme activity clearly showed a good correlation between these two quantities and growth speed. From an analogy with the Characean banding, the spatio-temporal organization via the cell membrane in electric potential and enzyme activity can be regarded as a dissipative structure arising far from equilibrium. These experimental results can be interpreted with a new mechanism that the dissipative structure is formed spontaneously along the whole root, accompanied by energy metabolism, to make H⁺ flow into the root tip.

DOI： 10.1016/0301-4622(87)80045-5

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Spatio-temporal patterns of electric potential produced by a root of azuki bean were investigated. It was found that the electric potential of a root shows a banding pattern surrounding the root and also a spontaneous oscillation. This electro-magnetic circumstance has a relation to its growth.

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