Figure 4.

Effect of the longitudinal incision spacing on the crack initiation moment of a PDMS film of 200 μm thickness. Here, λ(∼4h or 800 μm) is the wavelength of instability (see figure 1). The ratio s/λ defines the degree of stress confinement of the film in the lateral direction. Note that the incision spacing has very little effect on crack initiation moment when s/λ>1. Significant increase in moment occurs for s/λ<1.