Fingertip friction and tactile perception of materials

Friction has been established as a relevant contribution to the perception of materials, often by introducing a tactile dimension described by the word pair sticky / slippery. While these adjectives suggest a material property, friction results from sliding contact between skin and material during tactile exploration. We will discuss results for fingertip friction during active exploration of materials and for related subjective judgements.

Randomly rough surfaces were created with independently varied topography and spectral distribution of roughness. We found that the tactile perception of similarity follows the amplitude of roughness at smaller length scale rather than the topographic resemblance. The interaction between surface asperities and fingertip skin led to higher friction for higher microscale roughness. Individual friction data allowed us to construct a psychometric curve which relates similarity decisions to differences in friction [1]. We will also discuss results for fibrillar surfaces where the bending of sub-millimeter scale fibrils determines the perception of similarity in sliding touch and include first results for a comparison between measured and perceived friction.

[1] R. Sahli, A. Prot, A. Wang, M.H. Müser, M. Piovarči, P. Didyk, R. Bennewitz, Tactile perception of randomly rough surfaces, Scientific Reports, 10 (2020) 15800.