A design model for bending and extensional ionic polymer transducers

Abstract

Ionomeric polymer transducers have received considerable attention in the past ten years due to their ability to generate large bending strain (~10%) and moderate stress at low applied voltages (~2V). Bending transducers made of an ionomeric polymer membrane sandwiched between two flexible electrodes deform through the expansion of one electrode and contraction of the opposite electrode due to cation displacement across the transducer. Recently the authors reported extensional actuation in ionic polymer transducers (Akle and Leo 2005). In this study we developed and experimentally supported a model that assumes the electrode as the active area in ionic polymer transducers. The electromechanical coupling is represented by a linear and quadratic terms of the charge accumulated at the electrode. The mechanism of charge accumulation in ionic polymer transducers is an electric double layer type process. This charge is correlated with the conductor-ionomer interfacial surface area. In this study we will model the accumulated charge as a function of electrode architecture. The linear and quadratic coefficients are calibrated experimentally for several types of ionic species, ionic liquid uptake levels, and electrode conductor species. A design model based on the previously developed models will predict the generated free strain and blocked force in bending and extensional ionic polymer transducers for the different design variables. The model is experimentally verified by building transducers using the Direct Assembly Process with variable electrode architectures. The thickness and conductor concentration in the electrode and membrane are varied