Background/purpose: Knowledge of the mechanical properties of the human skin is very important for cosmetic and clinical research. Objective and quantitative measurements are essential to compare studies performed by different experimenters in different centres. The aim of this paper is to present a method to measure the viscoelastic properties of human skin in vivo using dynamic indentation. Methods: A complete device to assess the stiffness and damping of skin has been developed. The frequency and strain amplitude range from 10 to 60 Hz and from 1 to 10 mm. Tests on pure elastic inert materials have been performed to validate the device. An in vivo study including dynamic indentation, suction test, hydration measurement and topographic analysis has been performed on 46 subjects aged from 18 to 70 years, divided into three groups. Results: Results on inert materials show the validity of the device developed. The mechanical behaviour of the skin can be described by a Kelvin-Voight model under dynamic

The human skin, the interface between the body and the outside environment, has a very complex mechanical behaviour. Knowledge of its in vivo mechanical characteristics is essential to characterize the effects of medical or cosmetic products. The aim of this work is to present a non-invasive device using dynamic indentation to quantify the viscoelastic properties of human skin in vivo. The frequency and strain amplitude are in the range of 10 to 60 Hz and 1 to 10 microm. The results on 4 subjects show that a Kelvin Voigt model describes the mechanical behaviour of in vivo human skin with dynamic indentation well. The frequency average values of stiffness and damping have also been used to compare skin properties. We found a stiffness value of 47.3 to 128.3 N/m, and damping of 0.08 to 0.121 N.s/m, corresponding to a complex modulus of 13.2 to 33.4 kPa. These results show the ability of this device to characterize viscoelastic properties of human skin.