A high energy dielectric-elastomer-amplified piezoelectric (DEAmP) to harvest low frequency motions

Abstract

A dielectric elastomer generator (DEG) needs a high voltage priming source and large operating strains to produce a specific energy output in excess of 1 J/kg. For small-scale energy harvesting applications like a heel-strike generator, there is limited space. Providing such a priming source and a large amount of strain in a constrained space is challenging. To address this challenge, we present a dielectric-elastomer-amplified piezoelectric (DEAmP) generator. The piezoelectric generator charges the DEG and the DEG amplifies the voltage of the charges placed on it. Using a piezoelectric as a priming source makes our system much more compact and autonomous than others that use batteries and amplifiers as priming sources. From analysis, we define conditions of operation where there is a net amplification by the DEG and identify optimal conditions where up to 250 times in amplification of output energy could be produced. To produce large deformation on the DE within a constrained space, we propose the ripple mode of deformation. A simple analytical model and a design plot of the ripple mode was presented. Following our analyses, we construct a 3D-printed prototype that would demonstrate gain in energy harvested from a generic source of motion, reminiscent to that of a human footfall. We showed that the piezoelectric generator used in our experiment singly produces a specific energy output of 0.16 mJ/g, whereas the DEAmP generator yields 0.29 mJ/g. We showed the capability of a DEAmP to deliver an amplified output as compared to a standalone piezoelectric, even when harvesting low frequency motions. We discuss several strategies to further enhance the performance of a DEAmP.