Modelling of Multilayer Perforated Electrodes for Dielectric Elastomer Actuator Applications

A dielectric elastomer actuator (DEA) is a capacitor with an elastomer as dielectric, sandwiched between two complaint electrodes. An electric potential difference applied across the electrodes results in an electric field that creates lateral motion in the device which can be used to perform mechanical work. However, both the dielectric as well as the electrodes needs to be mechanically compliant. In order to achieve high stretchability, carbon nanotube (CNT) based thin films are used as electrodes to maintain conductance even at large mechanical strains. These electrodes are typically fabricated using spray coating or filter transfer method and resemble a perforated electrode under high magnification. Hence, there can be loss of field and stray capacitance when multiple layers of carbon nanotube based electrodes are used. This paper presents theoretical modelling and finite element analysis (FEA) simulations to study the nature of electric field and the effect it has on capacitance of multilayered perforated electrodes for various dimensions and geometric properties of the electrodes. We find that capacitance decreases sharply as the perforation is increased, however, for small uniform perforations (<20%), the decrease in capacitance is found to be negligible (~0.5%). This analysis is important to develop compact models for DEAs for faster simulation of such actuator structures.