A number of new developments have taken place over the years with respect to mechanical energy harvesting. However, significant progress is yet to be made to improve the energy density to sufficiently and reliably power our everyday mobile devices and other applications. Recently, a new approach in energy harvesting based on the principles of reverse electroactuation has been reported and is drawing much interest. Reverse electroactuation can be considered the opposite of electrowetting-on-dielectric, which is the manipulation of liquid droplets on dielectric with applied voltage. The reverse electroactuation approach of energy harvesting adopts a fundamental principle that the movements of liquid droplets on a dielectric film generate power by dynamically modulating the liquid-solid interfacial dielectric capacitance. The amount of power generated using this approach depends on various factors such as the type of conducting liquid used, dielectric coating type and thickness, and droplet pinning. Power densities up to 10³ W/m² have been reported using reverse electroactuation with Mercury as electrolyte, but using Mercury for real applications is not feasible due to its toxicity. In this study, we test a number of alternative conducting liquids as well as dielectric coatings in reverse electroactuation. The main objective is to observe and analyze the effect electrolyte and dielectric coatings have on power density and to compare the experimental results to previously published theoretical models. In addition to improving energy harvesting, this research contributes to fundamental understanding of how liquid movement under the combined influence of pressure, surface tension, and electric fields affect charge density. This may impact the design and development of porous materials for applications such as supercapacitors, electrodialysis, and reverse osmosis.

Figure 1. In reverse electroactuation, a conducting liquid droplet is placed between two electrodes, one of which is insulated (A). A dynamic mechanical loading deflects the droplet, resulting in a modulating capacitance and therefore an electrical current (B).