Origin and future of hydration lubrication

Abstract: Some of the biological surfaces, gels, boundary films, and graft polymerized surfaces are coated with gel layer or polymer brush. It seems that low friction results from a common lubricationmechanism while they have been studied dependently. This paper defines hydration lubrication reviews the study in each field and gives future prospects. Polymers adsorbed densely in good solvent expand in normal direction to the surface and form a brush-like structure. The brush is compressed and a repulsive force arises with an approach of another body and the applied force is supported by fluid. Polymer brush is pro-duced by means of graft polymerization. It is possible to reduce friction and wear of catheters and artificial joints by graft polymerization. Hydration lubrication is inevitable in preventing wear of articular cartilage. Hydrated surface layer on the internal wall of human small intestine assists digestion and prevents the wall from injury. Thus, hydration lubrication is an important subject of biomechanics and may be useful for medical treatments and machine elements