High actuation strain in silicone dielectric elastomer actuators with silver electrodes

Abstract

Conductive grease and powder are commonly applied as compliant electrodes for dielectric elastomer actuators (DEAs). Unfortunately, they can be rubbed off easily and DEAs based on them cannot self-heal from localised electrical breakdowns. Metallic thin films are cleaner and more resilient alternatives for electrodes. They are currently widely used in metalized plastic capacitors, which are known for their self-healing capability. However, they are not widely used in DEAs due to limitations in strain. In this paper, we demonstrate that a metalized DEA is capable of areal strains of up to 21%. The inexpensive and simple method of electroless silver deposition had been used to create the electrodes for the single-layer DEA. The lightly pre-stretched 80μm thick dielectric film demonstrated a 21% areal strain, which is a 17% reduction in thickness, with an applied voltage of 2.5kV. Self-healing properties of the silver electrodes have also been observed. Localised breakdowns of the dielectric film self-healed, thereby averting electrical breakdown and allowing actuation to continue, even at higher applied voltages. With higher breakdown voltages, larger breakdown fields were obtained, which would in turn lead to greater electrostatic forces. Relatively high breakdown fields of up to 75 MV/m were obtained. This is in contrast to the 35 MV/m obtained by silver grease under the same conditions. In mechanical strain tests, the silver films remained conductive while subjected to a uni-axial mechanical strain of up to 50%, which ascertains the ability of such electrodes to sustain high strains.