A new approach to describe the skin surface physical properties in vivo

In the present paper, we describe a new mechanical method characterising the physico-chemical properties of human skin and their variations along with liquid exposure scenario to the skin surface. A specific bio-tribometer has been developed to study the physical properties of the skin in vivo by measuring the maximum adhesion force between the skin and the bio-tribometer. We showed that the lipidic film present on skin surface was responsible for skin adhesion due to capillary phenomena. The measure of pull-off force between skin and bio-tribometer has permitted to estimate the liquid/vapour surface tension of the lipidic film (γLV ≈ 6.3 mJ/m2 in 30-year-old volunteer). The kinetic of sorption/desorption (sorption means indifferently adsorption and absorption process) of distilled water from the skin has been observed through the variation of the indenter/skin pull-off force versus time after distilled water application to the skin surface. This permits to follow in real time the variation of the skin physico-chemical properties after liquid application onto the skin surface. Finally, the increasing of skin friction coefficient after distilled water application onto skin surface was explained by the capillary adhesion force between the probe and the skin.