The role of the skin microrelief in the contact behaviour of human skin: Contact between the human finger and regular surface textures

The friction behaviour of the human fingerpad as a function of asperity geometry was investigated experimentally. Surface textures consisting of evenly distributed spherically tipped asperities were used for in vivo testing. Using analytical expressions, a multi-scale model was developed to explain the observed friction behaviour as a function of texture geometry, load and skin properties. Friction is found to increase with increasing tip radius. A minimum value for the coefficient of friction seems to exist as a function of asperity density. A maximum value for tip spacing exists above which the contact is not determined by the texture properties only. According to the model normal adhesion plays an important role in the observed friction behaviour.

► The complex behaviour of the fingerpad sliding against a textured surface can be explained using relatively simple expressions.
► A multi-scale model estimates the friction as a function of asperity geometry and operational conditions.
► The coefficient of friction increases with increasing asperity tip radius due to the effect of adhesion.
► The coefficient of friction shows a minimum as a function of asperity density.
► High friction is observed at high and low asperity density due to respectively high adhesion or high deformation.