Response of dielectric elastomer actuators

Elastomer films sandwiched between compliant electrodes work as electrostatic actuators when a large electric field is applied over the electrodes. We have analyzed the mechanical and electrical response of actuators to a sinusoidal varying driving voltage. The actuator acts as a capacitor in the electric circuit, but due to very high strains, the capacitance changes during a work cycle. The extension of the actuator is electrostrictive in response, hence it depends on the square of the applied field and oscillates with twice the driving frequency. The response is non-linear. This change in dimension is coupled back into the electric circuit through the capacitance of the film and the current oscillates with the first, third and odd higher-order harmonics. Due to this coupling, measurements of the current allows one to determine the expansion of the actuator, and hence to control the actuator.