On the role of adhesive forces in the tribo-mechanical performance of ex vivo human skin

The frictional performance of ex vivo skin was studied in a range of pressures between 0.5 and 20 kPa. Modifications in the coefficient of friction under different conditions stressed the important role of adhesion. The friction coefficient of “untreated” skin was obtained between 2.3-0.5, between 5.5 and 0.65 for wet skin and in a range between 0.65 and 0.35 for oil-covered skin. The contribution of capillary adhesion under wet conditions was analysed by the Hertzian and JKR contact models. The high coefficient of friction obtained under wet conditions could not be explained by the softening effect of the stratum corneum and capillary adhesion only. The results suggested a further influence of water in the physicochemical properties of the stratum corneum with a subsequent effect on friction.