Versatile origami micro-supercapacitors array as a wind energy harvester

The increasing growth in demand of portable and wearable electronics impels the exploration for flexible and integrated energy storage devices. Owing to the predominant advantages of cost-effectiveness, flexibility, and easy-processing, paper-based micro-supercapacitors have attracted extensive attention. In this study, the integrated polypyrrole/graphene-based micro-supercapacitors (PPyG-MSCs) array on printed paper was fabricated through a facile and straight-forward templating & imprinting strategy. By simply pressing the polypyrrole/graphene pieces into a mask, the micro-supercapacitor electrodes were easily embedded and fixed on the paper, which can effectively maintain the integrity and stability of electrode patterns. Consequently, the paper-based PPyG-MSCs show outstanding flexibility and mechanical stability, in which a single capacitor unit exhibits a high specific capacity of 22 mF cm^-2. The voltage and current output of the PPyG-MSCs array on paper can be well-regulated by directly folding the paper. More importantly, the PPyG-MSCs are easily assembled onto the wind energy appliance by patterning the electrodes into the leaves of the windmill to utilize and store the wind energy. This study opens up new opportunities for large-scale fabrication of flexible paper-based energy devices and presents an example for the reutilization of renewable energies.