Figure 2

Optical microscope images of a 180-nm-thick Ti film on PDMS substrate. (a) Before straining, under different uniaxial strains of (b) 10%, (c) 30%, (d) 50%, (e) 80%, and (f) after strain relaxation. The inset in (f) is a SEM image of the sample after strain relaxation. In (b), the straining direction and the presence of both vertical cracks and buckling are indicated, and in (c, d, e), the straining direction and angles between the secondary cracks and the straining direction are shown. LSM images of the sample at (g) 30% and (h) 50% strain. Green dotted lines are shown to estimate the average crack widths at the respective strains. Scale bars are 20 μm for (a, b, c, d, e, f) and 2 μm for (g) and (h).