Electroactuation with single charge carrier ionomers: The roles of electrostatic pressure and steric strain

We develop a theory for electroactuators with single charge carrier ionomers that reveals the interplay between the effects of electrostatic pressure resulting from ionic repulsion, and of the steric strain caused by the volume of ions in the double layer (and missing from the depletion layer). The theory shows that the electrostatic pressure can either reinforce or compete with steric strain, depending on the effective volume of the polarized ions in the double layer. Theoretical predictions are obtained for the electroactuator equilibrium deflection and bending dynamics, showing good agreement with available experimental data. Insights are offered into two directions of rational design of smart ionomer materials for actuators.