Figure 3

Optical microscope and LSM images of Ti films on PDMS substrates at a strain of 50%. Optical microscope images of (a) 80 nm, (b) 180 nm, and (c) 250 nm on PDMS substrates at an identical strain of 50%. In (a, b, c), the straining direction and the directions of primary cracks and secondary cracks are displayed. LSM images of (d) 180-nm and (e) 250-nm Ti films on PDMS substrates at the same strain (50%). Cracks in the 250-nm sample look narrower compared to the 180-nm sample. Scale bars are 50 μm for (a, b, c) and 10 μm for (d, e).