Stretchable Kirigami Polyvinylidene Difluoride Thin Films for Energy Harvesting: Design, Analysis, and Performance

$K\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i$, the extension of origami to include cutting as well as folding of a sheet, continues to gain attention as a design principle for functional materials. Using theoretical analysis, numerical simulations, and experiments, the authors apply kirigami patterns to enhance both the piezoelectric energy generation and stretchability of polyvinylidene difluoride (PVDF) films. Compared to everyday, cut-free PVDF films, kirigami films with patterned cuts can withstand much higher axial stretch, while maintaining the same level of voltage output. This approach enables, for example, tunable generators for integration into biomedical devices that are powered by the patient's own movements.