Actuated strains in excess of 100% in dielectric elastomer actuators using silver film electrodes

Metallic thin films have not often been used as electrodes in dielectric elastomer actuators (DEAs) as the reported actuated strains have been small. This is especially so when compared to commonly used conductive greases and powders. Here, the use of thin silver films formed by electroless deposition (ELD silver) as electrodes in DEAs is studied. As electroless deposition involves only the use of chemicals, expensive equipment is not needed. That, coupled with the fact that the thin silver electrodes require only a small amount of silver per unit area, means that such electrodes are simple and inexpensive to fabricate. In addition, unlike conductive powders and greases, these silver films adhere well to most substrates that are or have been made hydrophilic. This is especially useful in maintaining structural integrity of the actuator, such as when DEA units need to be stacked up one on top of each other. Most importantly, thin silver film electrodes have the ability to self heal. Self-healing not only averts actuator failure brought about by localised breakdowns, it also enables actuation to resume, even allowing higher driving voltages to be reached. In this paper, we demonstrate that DEAs with corrugated ELD silver electrodes can allow actuated area strains of up to 125% at a relatively low driving voltage of 1.9 kV. This is due to the low stiffening effect that the corrugated ELD silver electrodes have on the dielectric layer, which was found to be close to that of graphite.