Frictional Properties On Silicone Material/Lower Limb Skin Interface

There exists a critical contact interface between the socket and the residual limb skin when amputees wearing prosthetic socket during exercise. Pressure and friction force on this interface will have an important impact on the stump skin, subcutaneous tissue, blood vessels and normal blood flowing and so on.Due to the badly design or unreasonable material selection, the excessive friction between the stump skin and prosthetic socket may clinically cause a great damage to the stump skin and bring tremendous anguish to the patient.Therefore, research of friction behavior on the prosthetic materials/stump interface has an important theoretical and practical significance for optimizing design of prosthetic materials and improving quality life of amputees.In this paper, the two interfaces:prosthetic socket/silicagel inner bushing and silicagel inner bushing/residual limb skin were simulated by using an UMT-II tribometer under a reciprocating sliding wear mode. The energy loss after the frictional test was calculated based on the theory of definite integral for irregular figure area. The surface characteristics of the limb skin and prosthetic materials were observed and analyzed by using an OLS11003D laser scanning confocal microscopy, a HY0580computer type universal material machine, a DSA100type video contact angle meter and a digital camera. The tribological behaviors on the two adjacent interfaces were investigated by means of tribology, biology and materials science. The main conclusions are drawn as follows:1. The relative sliding occurred on the both silicone material/skin interface and prosthetic socket/silicone material interface at the beginning of the reciprocating wear mode, consequently, the friction coefficient was relatively high. Then it decreased and gradually reached steady with the adhesion appearing on the interfaces.2. The coarse convex on the back of silicone material induced the adhesion between the silicone material and skin increasing, which resulted in less friction and energy consumption. The knitting structure on the front of silicone material not only increased the relative sliding、 friction coefficient and frictional energy between silicone material and prosthetic socket, but also decreased the elastic deformation between the back of silicone material and skin during reciprocating frictional process. Thereby, the friction coefficient and the energy consumption on the interface reduced.3. The compression test of silicone materials under different loading conditions shows that the platform period appeared in the load of4.5N for all the four kinds of silicone material and all the material exhibited creep characteristics. The deformations of number1 and4material were less than that of number2and4material under the same loading, which indicated that the structure on the surface of the material can cushion the skin pressure.4. The silicone material with the coarse convex on the back and the knitting structure on the reverse side would reduce the friction energy consumption, skin heating and deformation, and lower the risk of skin damage.