Experimental measurement and quantification of frictional contact between biological surfaces experiencing large deformation and slip.

Interactions between contacting biological surfaces may play significant roles in physiological and pathological processes. Theoretical models have described some special cases of contact, using one or more simplifying assumptions. Experimental quantification of contact could help to validate theoretical analyses. The objective of this study was to develop a general mathematical approach describing the dynamics of deformation and relative surface motion between contacting bodies and to implement this approach to describe the contact between two experimentally tracked tissue surfaces. A theoretical formulation (in 2-D and 3-D) of contact using the movement of discrete tissue markers is described. The method was validated using theoretically generated 3-D datasets, with <1% error for a wide range of parameters. The method was applied to the contact loading of opposing articular cartilage tissues, where displacements of cell nuclei were tracked optically and used to quantify the movements and deformations of the surfaces. Compared to tissues with matched material properties, tissues with mismatched material properties exhibited increased disparities in lateral expansion and relative motion (sliding) between the contacting surfaces.