Dielectric-elastomer-enhanced triboelectric nanogenerator with amplified outputs

Abstract

Dielectric elastomers are effective ambient motion energy harvesters due to their flexibility, high energy density, and their ability to match low frequency unsteady motions. However, the dielectric elastomer generator (DEG) is in reality a charge pump, which requires an external supply of electrical charge to work as an energy harvester. In this work, the DEG is coupled with a contact-mode triboelectric nanogenerator (TENG) to form a hybrid. The TENG autonomously produces charges by contact electrification and the DEG in turn amplifies the electrical output by raising the charges to a higher electrical potential. In addition, dielectric elastomer exhibits dielectric strength two orders of magnitude higher than air, thus enabling delivery of a higher output voltage than that by TENG only. Both the TENG and the DEG converts mechanical motion to electrical energy via capacitance change. This makes them physically compatible for easy integration. We first analyze the coupled system and identify the optimal conditions that maximizes output yield in the shortest amount of time. We found that, the maximum output was realized when the TENG and DEG were excited perfectly out-of-phase for same input frequency. We showed that the DEG is ideally able to amplify the voltage output from TENG that is proportional to the capacitance change ratio of the DEG. By the same token, the maximum power will also be amplified proportionally for a constant current system. Our experiment showed that 260% and 180% DEG capacitance change can produce saturation voltage amplification of 2.7 and 2, respectively. Our work demonstrated dielectric-elastomer-enhanced output of a TENG and presented the optimal conditions for maximal amplification.