Electroactive Polymers (EAP): Simulation Studies of the Actuation Mechanisms in a Cantilever Cellulose Electroactive Paper

Electroactive polymers (EAPs) exhibit large strain in response to an external electric field and have attracted a great deal of attention in recent years for sensor and actuator applications. Favorable properties include soft actuation, ease and simplicity in manufacturing, being light-weight, low power consumption, and the ability to withstand harsh environments. However, this is an emerging material, and several aspects, including the fundamental mechanisms for piezoelectric deflections, remain unclear. This project studies the internal electromechanical factors that contribute to the voltage induced deflections of electro-active paper (EAPap). Experimental measurements of bias dependent deflections and water absorption as a function of time and relative humidity are obtained for the cellulose sensor through collaborative work with Norfolk State University. Mathematical models have been developed to predict EAPap deflections for a given set of operating conditions such as geometry, applied voltage, water and ion content. The simulations are performed to probe and quantify the role of the various internal mechanisms. Our simulations predictions yield good agreement with the measured data on the EAPap deflections. The modeling suggests that internal ion content and its migration, water absorption leading to a non-uniform permittivity, random variations in the transverse piezoelectric-coupling coefficient d31,i and the modulus of elasticity, all collectively contribute to the EAPap deflection electro-physics. It also appears that higher sensitivity, with a minimal bias dependence, could be achieved by deliberately adding ions during EAPap processing.