Electrets substituting external bias voltage in dielectric elastomer generators: application to human motion

Dielectric elastomer generators offer great potential for soft applications involving fluid or human interactions. These scavengers are light, compliant, have a wide range of functions and develop an important energy density. Nevertheless, these systems are passive and require an external bias source, namely a high voltage source and complex power circuits. This cumbersome polarization complexes the system in a drastic way and slows down the development of dielectric generators. In order to remove these problems, we propose here new transducers based on the use of an electret coupled with dielectric elastomer, thus avoiding the use of a high external voltage source, and leading to the design of a soft autonomous dielectric generator. By combining a dielectric model and the electret theory, an electromechanical model was developed to evaluate the capabilities of such a generator. This generator was then produced starting from Teflon™ as electret and silicone PolyPower™ as electroactive polymer. A good agreement between the model and the experiment were obtained. An experimental energy density of 0.55 mJ g −1 was reached for 50% strain (electret potential of −1000 V). Once optimized in its design, such a soft generator could produce energy density up to 1.42 mJ g −1 . An energy density of 4.16 mJ g −1 is expected with an electret potential of −2000 V.