Wrinkling of the human skin

The equations of a thin elastic shell resting upon a continuum foundation are written in a form suitable for application to the human skin and soft underlying tissues. Included are the effects of large deformation, arbitrary geometry, bending stiffness of the surface, and the finite thickness of the flexible foundation. Attention is focused upon the mechanics of skin wrinkling. A precise mathematical definition of “wrinkle lines” in the skin is given. Various simplified theories for determining the far postbuckling state of the skin are developed. One of these theories, called “wrinkle theory”, may be used to calculate the direction of the wrinkle line field formed over a large portion of the human skin by the natural action of the frame and muscles.