Energy harvesting with dielectric elastomer tubes: active and (responsive materials-based) passive approaches

Mechanical to electrical energy conversion is a well-established energy transduction approach. However, cases in which a mechanical energy source is not available call for new approaches to harvest electrical energy. In the present study, we demonstrate energy harvesting in soft dielectric elastomer (DE) tubes. Broadly, energy harvesting is obtained through inflation of the tube, electrical charging of the DE layer, and deflation, which results in a decrease in capacitance and an increase in voltage. We propose two methods to mechanically charge (or inflate) the system: (1) active, in which the tube is inflated through the application of mechanical pressure, and (2) passive, in which a passive cylindrical component placed inside the DE tube deforms radially in response to an environmental stimulus such as thermal excitation or water uptake and inflates the DE tube. To demonstrate passive charging, we consider gels as the passive component and employ well-known models with the properties of the commonly employed DE VHB 4910 to simulate the mechanical response of the system and estimate the harvested electrical energy. Our findings reveal that energy-densities in the order of similar to 10-50 mJ cm-3 can be harvested. The proposed approach and the inclusion of a passive component to mechanically charge the system opens new opportunities to generate energy in environments lacking traditional mechanical energy sources.