Assessing the Mechanical-to-Electrical Energy Conversion Process of a Droplet Sliding on the Poly(tetrafluoroethylene) Surface

Utilizing moving droplets to generate electricity has garnered significant attention due to its high output voltage and power. However, the understanding of energy dissipation and conversion processes during droplet movement remains limited, hindering the development of effective ways to further enhance the device's performance. In this study, we developed a method to simultaneously evaluate the input mechanical energy and output electrical energy while droplets slide on a poly(tetrafluoroethylene) (PTFE) surface to assess the energy conversion process. The influences of ion concentration, droplet volume, and contact area with PTFE on the energy conversion efficiency were investigated, suggesting optimized parameters. Moreover, by introduction of an asymmetric electric field on the PTFE surface, the input mechanical energy can be significantly reduced. In combination with the enhanced electrical output originating from improved surface charge density, the energy conversion efficiency is improved by an order of magnitude from 0.61 to 9.08%. These results shed light on strategies to improve device performance based on moving droplets.