Fig. 4: Stretchability of the wrinkled polymer thin film.

Electrical resistance changes under uniaxial strain (a) and biaxial strain (c). Sequential optical microscope images of the wrinkle deformation with uniaxial strain (b) and biaxial strain (d) using wrinkled RP-T50-COOH samples. Yellow arrows indicate crack formation. e Schematic illustration of the deforming and crack formation mechanism in the wrinkled RP-T50-COOH film under uniaxial strain. f Resistance change versus tensile strain depending on the average wavelength of wrinkles using wrinkled RP-T50-COOH film. g Uniaxial cyclic test to confirm the mechanical robustness for wrinkled RP-T5-COOH film. Inset: the magnified view of the graph. Error bars in a, c and f represent mean ± s.d., with n = 3.