Publisher：Tribology International  

The present study focuses on friction evaluation of the polyvinyl alcohol (PVA) hydrogel layer, an anticipative material for cartilage replacement. The experiments were carried out in a ball-in-socket configuration using a pendulum hip simulator. The friction coefficients of ceramic-on-hydrogel pairs were compared with those of commercial implants (metal/ceramic heads vs UHMWPE, HXPE and metal/ceramic sockets). The effects of hydrogel ageing and hydration were studied, among others. The use of PVA inserts caused up to 98% reduction in friction coefficient compared to original hip pairs. The application of PVA for local or even complete cartilage replacement seems to be an outstanding opportunity in implantology.

DOI： 10.1016/j.triboint.2022.108100

Web of Science

Scopus

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>The purpose of this study is to elucidate the boundary lubrication mechanism of the cooperation of hyaluronic acid (HA) and phospholipids (DPPC) between articular cartilages. As the cartilage tissue model, polyvinyl alcohol (PVA) hydrogel, which has similar water content and elasticity. PVA hydrogel was prepared as follows; PVA powder was solved into deionized water completely, then set in an environmental tester for repeat freezing and thawing to grow physical crosslinks. A rotational rheometer was used for the friction test since this apparatus could realize the evaluation in wide sliding velocity, between 10^-5 to 10³ mm/s. As a result, characteristic frictional behavior was observed, friction coefficient increased in the boundary lubrication range with sliding velocity. Comparing PBS, adding HA and DPPC changed the friction behavior. Especially, 0.02wt% of DPPC solution indicated a significant friction reduction, with or without HA. And in the case of 0.01wt% of DPPC, friction decreased with HA concentration. These results implied that the roles of HA and DPPC for the friction were different and the appropriate ratio of them would exist to minimize friction.</p>

DOI： 10.1299/jsmemecj.2023.j113p-10

CiNii Research

Publisher：Polymers for Advanced Technologies  

Recent studies have found a rapid increase of ultrahigh molecular weight polyethylene (UHMWPE) wear in the presence of proteins from the synovial fluid. Due to UHMWPE's high hydrophobicity, it tends to adsorb a tremendous amount of proteins. Moreover, since UHMWPE has low thermal conductivity, a temperature rise in the center of the contact area due to frictional heating could cause protein denaturation from the synovial fluid. It has been shown that the denatured protein may increase the adhesive wear response. This study aimed to address the effects of graphite and graphene oxide (GO) addition on the wear properties of UHMWPE in protein environments. The surface properties were characterized using surface roughness profiler, surface energy evaluation, zeta potential, and Fourier transform infra-red (FTIR). Following that, wear properties of UHMWPE composite were evaluated using a multidirectional pin-on-disc wear test under a bovine serum lubricated condition. The worn surface of the UHMWPE composite sample was evaluated, and the dominating factors of wear properties were determined. The effect of protein adsorption on the composite surface was also assessed after the wear test. The hydrophilicity of UHWMPE/1.0GO is considered to be the dominant contribution determining protein adsorption in static conditions. UHMWPE composite's wear resistance improvement was primarily dominated by GO filler (1.0 wt%) near the sliding surface, which has improved the subsurface strength of the material and heat dissipation effect, which reduces the denaturation of the proteins.

DOI： 10.1002/pat.5651

Web of Science

Scopus

Publisher：Tribology International  

Inclusion of 25 wt% of UHMPWE particles to SU-8 improved the tribological properties and restricted crack propagation within the matrix. Further adding 0.2 wt% and 0.5 wt% of hyaluronic acid (HA) reduced friction and wear. Worn surface morphology revealed that the HA-filled composite has less damage and smoother appearance than the composite without HA. The phenomenon of HA lubrication was attributed to the lubricating film formation ability of HA. Also, HA induced hardness has positively influenced the wear rate of SU-8 composites. These promising results of SU-8/UHMWPE/HA composites make them potential candidate as future hip implant material.

DOI： 10.1016/j.triboint.2021.107399

Web of Science

Scopus