Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Naotomo Tottori Last modified date:2021.07.08

Assistant Professor / Department of Mechanical Engineering / Faculty of Engineering


Presentations
1. Akiho Hirao, Naotomo Tottori, Maasa Yokomori, Miho Tagawa, Shigeo S. Sugano, Shinya Sakuma, and Yoko Yamanishi, Protein crystallization in microdroplets with the aid of electrically induced microbubbles, The 34th IEEE Int. Conf. on Micro Electro Mechanical Systems, IEEE MEMS 2021, 2021.01.
2. Guangchong Ji, Naotomo Tottori, and Takasi Nisisako,, Lactic acid bacteria of different shpaes flowing through deterministic lateral displacement microarrays, The 18th International Conference on Precision Engineering (ICPE2020), 2020.11.
3. Naotomo Tottori, and Takasi Nisisako, Continuous generation of cell-laden microgels through deterministic lateral displacement arrays, The 24th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2020, 2020.10.
4. Naotomo Tottori, Takasi Nisisako, Degas-driven microfluidic deterministic lateral displacement, 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018, 2018.01, We report degas-driven deterministic lateral displacement (DLD) for size-based particles enrichment and separation by using polydimethylsiloxane (PDMS) gas solubility. Unlike conventional DLDs which normally require external pumping equipment, we have employed degas-driven flow of a PDMS device to infuse a sample solution into a DLD array. We have demonstrated DLD-based enrichment and separation of differently sized microbeads. Furthermore, separation of white blood cells (WBCs) and red blood cells (RBCs) in whole blood was also demonstrated..
5. Naotomo Tottori, Liu Yingzhe, Takasi Nisisako, Functional particles design using deterministic lateral displacement, 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018, 2018.01, We propose novel deterministic lateral displacement (DLD) devices that enable separation and reaction simultaneously for producing functional particles. Firstly, we produced spherical Ca-alginate gel particles without satellite droplets by producing and transporting Na-alginate droplets across the CaCl2 emulsion stream through DLD micropillars. We also demonstrate polyelectrolyte coating onto polystyrene microspheres using multiple laminar streams flowing through DLD micropillars..
6. Seungman Choi, Naotomo Tottori, Takasi Nisisako, Mechanically and directionally tunable soft step emulsification, 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018, 2018.01, We propose a novel concept, Soft Step Emulsification (SSE): actively-tunable geometry-dependent droplet generation in an elastic device. By mechanically stretching a whole device made of polydimethylsiloxane (PDMS), we induce deformation of internally confined micro nozzles, tuning the droplet break-off in step emulsification. The shrinkage/expansion of the nozzles could be switched when changing directions of stretching by 90°, allowing us to flexibly tune the sizes of water-in-oil (W/O) droplets in the combined range of 9-18 µm with CVs of 5-8%..
7. Yingzhe Liu, Naotomo Tottori, Takasi Nisisako, Microfluidic external gelation of shape-controlled calcium-alginate hydrogels for drug encapsulation and sustained release, 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018, 2018.01, We report microfluidic in-situ external gelation for preparing calcium(Ca)-alginate hydrogels of precisely defined shapes for controlled drug release. We demonstrated that homogeneous spatial distribution of reactant CaCl2emulsions around precursor sodium(Na)-alginate droplets is essential to obtain highly spherical hydrogels. UV-Vis measurement was performed to demonstrate sustained release of encapsulated anti-fouling drug Irgarol. Magneto-responsive Janus gels and hemi-spherical gels made from Na-alginate/Grycerol Janus droplets are also presented..
8. Hiroto Komiyama, Naotomo Tottori, Takasi Nisisako, Microfluidic grooves-on-slits devices for massively parallel droplets production, 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018, 2018.01, We propose a simple droplet-production module with grooves crossing over slits. Our test modules consist of two detachable elements: (a) a PDMS chip with microfabricated open grooves with matrix or circular arrangement, and (b) stainless-steel parts with three linear or annular parallel slits for world-to-chip interface. By assembling the two elements so that the on-chip microgrooves cross over the slits, we demonstrated parallelization of 100–1250 microfluidic droplet generators (MFDGs) of 10–100 μm sizes for mass-producing water-in-oil (W/O) droplets..
9. Naotomo Tottori, Takasi Nisisako, Particles separation via sheath-free deterministic lateral displacement with inertially focused single input, 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017, 2020.01, We report sheath-free deterministic lateral displacement (DLD) for size-based particles separation by using inertial focusing in a single input stream. Unlike conventional DLDs which require sheath streams to focus a particles-containing solution before DLD arrays, we have employed inertial focusing to align particles along the center or sidewalls of the input channel. We have demonstrated inertial focusing and DLD-based separation of differently sized microbeads..
10. Naotomo Tottori, Takasi Nisisako, Sheathless deterministic lateral displacement for continuous particle separation in viscoelastic fluid, 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017, 2020.01, We present sheathless deterministic lateral displacement (DLD) for particles separation by using elasto-inertial focusing in a single input stream. Instead of conventional DLDs which require sheath buffer streams to focus a particles-containing sample solution before DLD arrays, we have employed elasto-inertial focusing to align particles along an input channel center line. We have demonstrated successful elasto-inertial focusing and microbeads separation based on their sizes in the DLD array..
11. N. Tottori, T. Nisisako, Y. Yanagida, T. Hatsuzawa, In situ separation of main and satellite droplets using a deterministic lateral displacement microfluidic device, 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016, 2016.01, We report the continuous and passive separation of main and satellite droplets using a deterministic lateral displacement (DLD) array coupled with a symmetric microfluidic droplet generator. In addition to the collection of the main water-in-oil droplets at 100% purity, fractionation of satellite populations of different sizes could be achieved through the multi-step hydrophobic DLD regions. Moreover, separation of main and satellite biphasic oil-in-water droplets was successfully demonstrated using a hydrophilic DLD device. To the best of our knowledge, this is the first report on the microfluidic separation of main and satellite droplets produced in a purely symmetric system..
12. N. Tottori, Y. Sakurai, T. Nisisako, Y. Yanagida, T. Hatsuzawa, Thermally tunable deterministic lateral displacement through hydrogel micro pillar arrays, 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016, 2016.01, We present a novel deterministic lateral displacement (DLD) microfluidic device with thermally tunable separation capability. To flexibly change the critical diameter (Dc) of the separation array, we fabricated DLD micropillars made of poly-N-isopropylacrylamide, a thermo-responsive hydrogel, in a polydimethyl siloxane microfluidic channel. The prepared DLD pillars shrunk at a high temperature (>30°C) and swelled at a low temperature (<30°C) in an aqueous solution because of their characteristic hydrophilic-hydrophobic phase transitions. By heating and cooling the DLD device across the transition temperature, the Dccould be continuously changed and the separation mode of the model particles could be switched..
13. Naotomo Tottori, Jongho Park, Yasuko Yanagida, Takeshi Hatsuzawa, Separation of viable cells using deterministic lateral displacement microfluidic device, 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2015, 2015.01, We report the first use of deterministic lateral displacement (DLD) microfluidic device for label-free separation of viable cells from nonviable cells. Cells in apoptosis status are physically smaller than viable cells. We focused on this phenomenon and have demonstrated the separation of viable cells from nonviable cells using DLD method, which can separate particles based on their sizes continuously without any labeling and external energy sources. We succeeded in the removal of 66.9% nonviable cells and also enrichment of viable cells..