A novel design concept to boost the force output of dielectric elastomer membrane actuators

Abstract

The structure of dielectric elastomer actuators (DEAs) is based on a thin elastomer layer, which is sandwiched in-between compliant electrodes. This capacitor like structure enables to build lightweight and energy efficient actuators with high design flexibility. An applied high voltage leads to a thickness compression and to a simultaneous area expansion of the elastomer, which can be exploited for actuation. Additionally, due to the capacitive nature of DEAs, the application of a DC voltage allows to maintain a position without consuming energy, making such actuators ideal for, e.g., valves. Despite being relatively easy to manufacture and providing large strokes, membrane DEAs suffer from low force outputs (for single layer systems). This paper presents a novel design concept which permits to retune the stroke-force trade-off of DEAs, by allowing to increase force output of the actuator at the expense of a reduced stroke. This is of particular interest for valve applications, which typically need high closing forces and low strokes in the submillimeter regime. The developed system is based on membrane DEAs biased with linear and non-linear springs. Such systems are typically known for high actuation strain and strokes but low force output, even lower in comparison to a single layer membrane DEA only. By means of the novel design concept, the force output of a single layer membrane DEA can be increased by a factor of 3 to 4. The novel actuator concept is initially illustrated, and subsequently validated via a graphical modeling concept on stripin- plane DEAs.