Low strain nanomechanics of collagen fibrils.

The high stiffness of collagenous tissues such as tendon and ligament is derived in large part from the mechanics and geometries of the constituent collagen's hierarchical forms. The primary structural unit in connective tissues is the collagen fibril for which there exists little direct mechanical or deformational study. Therefore, the current understanding of the mechanisms involved is extrapolated from whole tissue data. To address this, the elastic response due to bending of readily extractable adult collagen fibrils was studied, and the results were compared to previously reported radial indentation experiments. A demonstration of a material anisotropy arising without loss of the assumptions of homogeneity is presented.