Polyelectrolyte Materials for Dielectric Elastomer Energy Harvesting

Abstract

Dielectric elastomers actuators are compliant capacitors which can convert electrical energy into mechanical energy [1]. The simplest device consists of a thin elastomer sheet sandwiched between two compliant electrodes. In actuation mode, a voltage is applied to the electrodes and the attractive Coulombic force between the opposing charges squeezes the elastomer causing it to expand perpendicular to the applied electric field. Since they are electrically driven, the response speed of DEAs is usually limited by the viscoelastic response of the constituent polymer. In terms of ease of delivering power, as well as response speed, DEAs are some of the most promising technologies for the emerging field of soft robotics [2]. However, existing DEA technologies are severely limited in three key areas. First, most elastomers require some amount of mechanical pre-strain in order to achieve large deformation. Typically the strain is maintained by application of a rigid frame that improves the performance of the elastomer, but negates most of the benefits associated with a soft, compliant actuator. Second, the fields required for actuation are high, in the 20-200 V/micron range, causing the actuation voltage to be relatively high (3 - 20 kV). While the DEAs themselves require low power inputs, the high voltage requirement greatly limits where DEAs can be used and how portable they can be, since high voltage power supplies are generally bulky and heavy. Third, since DEAs are compliant capacitors, the strain in the electrodes has to match the strain in the elastomer. There are extremely few materials which can conduct electricity, bond well to an elastomer,