An Innovative Tool to Measure Human Skin Strain Distribution in Vivo using Motion Capture and Delaunay Mesh

Abstract

AbstractSkin has a complex structure and its deformation mechanics is still not well defined. In the study of skin biomechanics, the stretch ratio, λ, is an important property, which is determined using strain data. This paper attempts to develop a novel tool by integrating experimental-numerical approach to measure full-field strain distribution of human skin in vivo. Skin deformation in vivo was measured using motion capture system, (which is not a full-field measuring tool) and then by constructing finite elements, its full-field strain contour is produced. The experimental procedure starts by attaching a set of reflective markers onto the skin at the forearm of healthy volunteers. Skin deformation is induced by pulling a nylon filament attached with a loading tab. Three infrared cameras are used to capture the movement of markers during load application. QTM (Qualisys, Sweden) software is used to track markers trajectories and generate data consisting of 3-dimensional markers coordinate. The initial capture is set as the reference marker positions (undeformed skin) and the subsequent images represent the deformed skin relative to the initial. Representing markers as nodes, finite elements are constructed by adjoining three adjacent markers using Delaunay mesh. Strains were deduced from the strain displacement matrix and measured for three subjects at three loading directions. The results are in fair agreement with those obtained by others. The method and output provide a useful addition to understanding skin deformation.