A mechanistic approach to predicting the friction behaviour of human skin

In this work, analytical models available from contact mechanics theory having a proven record in mechanical engineering were used to develop a model predicting the friction behavior of human skin. A multi-scale contact model was developed in which the contact parameters are calculated at three levels, each level characterized by its elastic behavior and geometry. For a product part in contact with the so-called hairy skin the skin topography can be described as being composed of spherical contacts, whereas for the finger in contact with a product surface the fingerprint ridges are modeled as annulus shaped line contacts. Sliding friction was measured in vivo between the skin and different surface textures produced using ultra-short pulsed laser technology. The results observed during in vivo experiments are very well explained by the developed model, which predicts the friction as a function of product geometry, asperity geometry and normal load.