Voltage control of the resonance frequency of dielectric electroactive polymer (DEAP) membranes

We report on the characterization, active tuning and modeling of the first mode resonance frequency of dielectric electroactive polymer (DEAP) membranes. Unlike other resonance frequency tuning techniques, the tuning procedure presented here requires no external actuators or variable elements. Compliant electrodes were sputtered or implanted on both sides of 20 to 35 m thick, 2 to 4 mm diameter polydimethylsiloxane (PDMS) membranes. The electrostatic force from an applied voltage adds compressive stress to the membrane, effectively softening the device and reducing its resonance frequency, in principle to zero at the buckling threshold. A reduction in resonance frequency up to 77% (limited by dielectric breakdown) from the initial value of 1620 Hz was observed at 1800 V for ion-implanted membranes, and a 20% decrease was observed for membranes with sputtered electrodes. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory. This model is more accurate in the tensile domain than the existing model for thick plates [33] applied to DEAPs. The membranes reported here have resonance frequencies in the audible range. By varying their resonance frequency (and hence their compliance) the membranes can be used as frequency-tunable attenuators. The same technology could also allow the fine-tuning of the resonance frequencies in the MHz range of devices made from much stiffer polymers such as PMMA or SU8.