Study On Frictional Properties At Surfacebionic Prosthesis Materials/Skin Interface

Amputation patients need preload to wear prosthetics,small preload will cause the relative sliding between prosthesis and skin interface,resulting in skin damage on the amputation patients,walking with less comfort and even fall of artificial limbs,while the big preload will lead to large elastic deformation of tissue under skin,causing that blood circulation is blocked and skin swelling or even necrosis.Therefore,the appropriate preload force could effectively minimize the relative sliding between the prosthesis and skin interface,improve its fitness to realize the ultimate goal of artificial material design.However,the relevant researches are rarely involved at home and abroad,especially there's few reports about the bionic surface design to improve the fitness between the interface and to reduce the friction energy loss.In this thesis,four different bionic surface textures are designed from the morphological structure of the gecko,and their surface features are analyzed by the use of DSA 100 Drop Shape Analyzer,OLS1100 laser scanning confocal microscope.By means of the UMT-II multifunctional friction and wear tester,the face-to-face contact mode for one-way and reciprocating friction is adopted for the simulation of motion pattern of the prosthetic material and skin interface.Based on the theory of definite integration of irregular figure area,the effects of different bionic surface texture,varied force and velocity on the interfacial friction characteristics are studied.The bionic surface structure of the prosthesis/skin interface is optimized from the perspective of interdisciplinary interaction of tribology,biology and materials science,and the mechanism of enhancing the adhesion of prosthetic limbs and skin is revealed in this thesis.The main conclusions are included as follows:1.Within four different biomimetic surface textures,the groove depth of the silica-gel material is less than the polyurethane material.The positive four prism structure can reduce the surface contact angle and improve the hydrophobicity of the solid surfa-ce,while the positive hexagonal prism and the cylinder can improve the solid surface contact angle and reduce the hydrophilic of the solid surface.The bionic surface struc-ture of the solid increases the surface energy and the adhesion mechanism of the soli-d surface.2.From the uniaxial friction tests for the surface of biomimetic prosthetic materia 1/skin interface,it has been found that initial sliding displacement increases with the in crease of positive pressure,and coefficient varies on the contrary.Also,the initial slidi-ng displacement and the average friction coefficient decrease with the increase of vel-ocity.3.The reciprocal friction test between the surface of biomimetic prosthetic materi al and skin finds that during the reciprocating friction the energy loss for one cycle inc-reases with the increased positive pressure.When the positive pressure is small,there is a relative slip for all the textures and the existing relative slip decreases with the in creased positive pressure.The effect of the velocity on the energy dissipation for one cycle is not significant.4.The advantages and disadvantages of bionic morphology are evaluated compre hensively,and the hexagonal prism is endowed with the best performance,followed by a smooth surface,and then the cylinder,the worst is the positive four prism.