Influence of physico-chemical, mechanical and morphological fingerpad properties on the frictional distinction of sticky/slippery surfaces.
This study investigates how the fingerpad hydrolipid film, shape, roughness and rigidity influence the friction when it rubs surfaces situated in the slippery psychophysical dimension. The studied counterparts comprised two 'real' (physical) surfaces and two 'virtual' surfaces. The latter were simulated with a tactile stimulator named STIMTAC. Thirteen women and 13 men rubbed their right forefingers against the different surfaces as their arms were displaced by a DC motor providing constant velocity and sliding distance. Tangential and normal forces were measured with a specific tribometer. The fingerpad hydrolipid film was characterized by Fourier transform infrared spectroscopy. The shape and roughness of fingers were extrapolated from replicas. Indentation measurements were carried out to determine fingerpad effective elastic modulus. A clear difference was observed between women and men in terms of friction behaviour. The concept of tactile frictional contrast (TFC) which was introduced quantifies an individual's propensity to distinguish two surfaces frictionally. The lipids/water ratio and water amount on the finger skin significantly influenced the TFC. A correlation was observed between the TFC and fingerpad roughness, i.e. the height of the fingerpad ridges. This is essentially owing to gender differences. A significant difference between men's and women's finger topography was also noted, because our results suggested that men have rougher fingers than women. The friction measurements did not correlate with the fingerpad curvature nor with the epidermal ridges' spatial period.
Département de Mécanique Appliquée, Institut FEMTO-ST, UMR CNRS 6174, UBFC, 24 rue de l'Epitaphe, 25000 Besançon, France.
Pierre-Henri
PH
Cornuault
Département de Mécanique Appliquée, Institut FEMTO-ST, UMR CNRS 6174, UBFC, 24 rue de l'Epitaphe, 25000 Besançon, France.
Luc
L
Carpentier
Laboratoire de Physique et Mécanique Textiles, Université Haute-Alsace, Ecole Nationale Supérieure d'Ingénieurs Sud Alsace, 11 rue Alfred Werner, 68093 Mulhouse Cedex, France marie-ange.bueno@uha.fr.
Marie-Ange
http://orcid.org/0000-0001-5067-217X
MA
Bueno
Département de Mécanique Appliquée, Institut FEMTO-ST, UMR CNRS 6174, UBFC, 24 rue de l'Epitaphe, 25000 Besançon, France.
Jean-Marc
JM
Cote
Département de Mécanique Appliquée, Institut FEMTO-ST, UMR CNRS 6174, UBFC, 24 rue de l'Epitaphe, 25000 Besançon, France.
Guy
G
Monteil
D055119:Elastic Modulus; D005260:Female; D005385:Fingers; D006801:Humans; D008297:Male; D008567:Membranes, Artificial; D012867:Skin; D013499:Surface Properties
D008567:Membranes, Artificial
biotribology; finger; friction; hydrolipid film; skin; tactile