Figure 4.

(a–d) Stress (a and b; in MPa) and strain (c and d; unitless) distributions for 2 kPa linear (a and c) and nonlinear (b and d) gels of 10 μm thickness with 600 Pa traction applied. Plots for the other stiffness linear gels have different magnitude but when normalized to maximum values look identical (data not shown). The stress contours are blunted and exhibit a pinched profile in the strain-stiffening material. In contrast, the strain profiles extend farther into the strain-stiffening material compared with the linear material, as can be seen by the lowest contour, representing roughly 9% of the maximum strain, touching the lower boundary in the 10-μm-thick nonlinear gel but not in the 10-μm-thick linear gel. See Supporting Material for plots for 1, 5, and 50 μm gels.