Figure 7.

Relaxation test. Temporal evolution of total area stretch ϑ, reversible elastic area stretch ϑ^e, and irreversible growth area stretch ϑ^g for displacement driven skin expansion. Horizontal dashed lines represent the elastic stretch limit beyond which skin growth is activated ϑ^crit, and the maximum area growth ϑ^max. Displacements are increased linearly up to the vertical dashed line and then held constant. Displacement control induces relaxation indicated through the gradual decrease in elastic stretch and stress, while the growth stretch increases at a constant total stretch.