Fig. 4.

Global displacement and strain fields in a contracting collagen gel. (a) Using Vic2D and images such as those shown in Fig. 3, the degree of bead displacement during gel contraction was calculated. This plot illustrates that displacement is greatest on the edges of the gel and lower, essentially zero, at the center of the gels. (b) Using Vic2D a strain map was calculated from the measured displacements; the strain field, strains are essentially a normalization with respect to the original distance between beads, are relatively uniform across the contracting collagen gels. The numerical approximation used to calculate strains from displacements results in some variations across the field