fig7

Figure 7. Flexible films with single-directional stretchability incorporating Kirigami patterns. (A) PET film with a single-cut Kirigami pattern, demonstrating tensile deformation up to 200%, along with twisting and bending. Reproduced with permission^[65]. Copyright 2020, Elsevier; (B) Photographs of a Kirigami pattern with only major cuts and a hybrid pattern featuring both major and additional cuts. Reproduced with permission^[66]. Copyright 2018, Springer Nature; (C) Images of the Kirigami pattern deformed under various strains and a freestanding nanosheet. Reproduced with permission^[67]. Copyright 2018, Wiley-VCH; (D) Electrothermal properties tested under tensile conditions from 0% to 200% strain, using a heating layer formed on a uniaxially cut cPI film substrate. Reproduced with permission^[68]. Copyright 2019, American Chemical Society. PET: Polyethylene terephthalate; cPI: clear polyimide.