Silicone dielectric elastomer actuators: Finite-elasticity model of actuation

A theory for the actuation strain of a silicone dielectric elastomer actuator with a simple geometry is developed. The stress is a function of two variables, the strain and the applied voltage. A lamination type stress-strain function was employed, due to the nature of the electrodes. All parameters are obtained from physical measurements. Then, measurements of the blocking force are shown to correspond to what is expected from the Maxwell stress. Actuation strain measurements are performed and compared with the developed theory. The developed model has no free parameters, yet it exhibits the features of the actuation strain: the optimum load is reproduced correctly (within the chosen experiment resolution of 5 g). The discrepancy on the actuation strain between the measurement results and the model vary between 15% and 37% at the optimum, which are ascribed to inaccuracies in dimension measurements of the actuator and the inherent crudeness in the assumption that the stress and strain fields are constant throughout the actuator. We conclude that even for high strains, the actuation of dielectric elastomer actuators is well described by only considering the elasticity of the material and the Maxwell stress due to the applied electric field.