Longitudinal variations in the Poisson's ratio of collagen fibrils

Atomic force microscopy imaging was used to determine the behavior of the D-banding geometry of collagen fibrils upon stretching in air under ambient conditions. The fibrils were strained by attaching them on a stretchable foil, the strain being monitored by the D-banding spacing and height. It was found that stretching fibrils increases the D-banding spacing and decreases the D-banding height. A simple, continuum mechanics model based on classical elasticity theory suggests that the gap has a smaller Poisson's ratio than the overlap region.