Characterizing skin using a three-axis parallel drive force-sensitive micro-robot.

There is a strong need to measure the complex mechanical properties of soft tissues such as skin. An in vivo experiment characterizing the mechanical response of human skin is presented. A rich set of deformations were applied to several positions on the arm using a novel force-sensitive micro-robot. All sites studied exhibit highly non-linear, anisotropic, and viscoelastic behavior. The experiments determined directions in which the skin response was stiffest. These directions agree with accepted orientations of Langer or relaxed skin tension lines.