Self-Clearing of Metalized Electrodes and its Impact on Electroactive Polymer (EAP) Based Actuators

Abstract

EAP based actuator technologies are extensively studied to design smart/intelligent systems ranging from deployable space structures, morphing wings, to medical devices and artificial muscles. Despite the extensive research on electroactive polymers (EAP), practical implementation of this technology is slow because of low induced forces and defect-driven premature electrical breakdown. Multilayered or stacked configuration can address the low induced force issue. However, construction procedure of multilayered sample is susceptible to more defects, which can further aggravate defect-driven premature breakdown of EAP actuators. Reducing the number of defects using self-clearing concept can improve the EAP actuators’ ability to withstand high electric fields. Self-clearing refers to the partial local breakdown of dielectric medium due to the presence of impurities, which in turn results in the evaporation of some of the metalized electrodes. After this evaporation, the impurity is cleared and any current path would be safely cut off, which means the actuator continues to perform, albeit with a reduced actuation area due to electrode evaporation. In this paper we study the impact of self-clearing metalized silver electrodes on the electrical and electromechanical behavior of EAPs, more specifically P(VDF-TrFE-CTFE) terpolymer. First, we use Weibull statistics to systematically estimate the self-clearing/preconditioning field needed to clear the defects. Then electrical breakdown experiments are conducted with and without preconditioning the samples to investigate their effects on the breakdown strength of the EAP. Finally, we implement this self-clearing/preconditioning field on single and multilayered P (VDF-TrFE-CTFE) unimorph actuators and investigate the resulting electromechanical performance. Due to preconditioning of the actuators using self-clearing concept, the actuators endure higher electric fields compared to a control sample. Loss of capacitance occurs during self-clearing, which in turn affects the electromechanical performance of the actuator. For that reason, we also report on the blocked force of preconditioned and controlled actuators to evaluate and compare their electromechanical performance.