Figure 1.

Wrinkling morphology observed in the experiments with substrate with no pre-stretch. (a) Sinusoidal wrinkling observed when the compressive strain was 0.1; (b) period-doubling mode observed at the overall compressive strain of 0.19. The experimental phenomenon is similar to that observed by Brau et al. [5]. PDMS was the substrate in our experiments. The stiff film was generated after the PDMS was subjected to a UV-ozone treatment for 10 min. Experiments details are given in appendix A. (Online version in colour.)