A Multiscale Model for the Indentation of Type-I Collagen Soft Tissue Equivalents

Indentation has become a popular research technique for the mechanical characterization of collagen-based soft tissues. The popularity of the method stems from its requirement of a modestly sized sample, from its ability to be applied in vitro as well as in vivo, and from the ready availability of instrumentation and analytical techniques borrowed from a long tradition of its application to non-biological materials. Many analytical models for the indentation of collagen-based soft tissues rely on a Hertzian contact model. Such a model emphasizes the contributions of an idealized material in compression over the contributions of the material in tension. However, this approach largely neglects the role of the collagen microstructure in soft tissue that has the capacity to carry far greater mechanical loads in tension rather than in compression.