Comparison of Elastic and Tactile Behavior of Human Skin and Elastomeric Materials Through Tribological Tests Khaled Elleuch, Riadh Elleuch Laboratoire des Syste ` mes Electro-me ´ canique (LASEM), Ecole Nationale d’Inge ´ nieurs de Sfax, Tunisie Hassan Zahouani Laboratoire de Tribologie et Dynamique des Syste ` mes (LTDS), UMR CNRS 5513, Ecole Centrale de Lyon, France The current article describes static and frictional contact tests carried out with spherical indenter on both human skin surface and elastomeric materials. This tribological study is performed to analyze the elasticity and tactile properties of the human skin, and therefore to evaluate reliability of human skin behavior simulation through the considered elastomeric materials. Finite element analyses of indentation tests are proposed. Critical normal load was found when numerical and experimental results were confronted. Such critical force defines the limit of elastic model application. POLYM. ENG. SCI., 46: 1715–1720, 2006. © 2006 Society of Plastics Engineers INTRODUCTION Ageing is a physiological mechanism associated with changes in skin morphology and mechanical properties, including dry state, and anisotropy of the skin relief. More- over, cosmetic products induce tactile changes of the skin surface [1]. Quality of the skin such as suppleness, smooth- ness, roughness, greasiness, or dryness is the combined result of the mechanical and frictional properties of the skin. A variety of techniques have been employed to evaluate skin friction [2, 3]. Since the human skin has viscoelastic behavior [4] and to avoid technical difficulties encountered when determining in vivo human skin behavior, it will be interesting to sim- ulate its elastic and tactile properties through elastomeric materials. In fact, the elastomeric materials have attractive proper- ties. In particular, they have shown viscoelastic behavior [5]. They can be easily deformed under a relatively weak load and often had a weak residual deformation [6, 7]. The aim of our study was to determine quantitatively the elastic and tactile properties of the human skin, and then compare these tribological properties with those obtained for two different elastomeric materials. EXPERIMENTAL Materials Human Skin. The study group consisted of three women (24, 25, and 26 years old). All participants were in good health. They were instructed not to apply any skin care product a day before testing. All measurements were per- formed after the subjects have been physically inactive for at least 15 min. Measurements were made on the volar aspect of their forearm. Thermoplastic Polyurethane Elastomer. Thermoplas- tic polyurethane elastomer (TPU) belongs to thermoplastic elastomers. The studied material is (PEARLTHANE D11T92EM), which is a polycaprolactone-copolyester based TPU, supplied in form of translucent, colorless or slightly yellowish pellets. This material can be extruded and injection-molded. Silastic. The second selected elastomer is called silastic “SIL.” It is used as replica material in many applications such as the practice of dentistry. This material was also chosen for its homogenous roughness. Moreover, its elastic property tended to simulate the physical in vivo skin prop- erties with an indentation in the material during the test in the same order as in the skin. Correspondence to: Khaled Elleuch; e-mail: Khaled.elleuch@enis.rnu.tn DOI 10.1002/pen.20637 Published online in Wiley InterScience (www.interscience. wiley.com). © 2006 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—2006