Effect of mechanical pre-stretch on the stabilization of dielectric elastomer actuation

A dielectric elastomer is capable of giant electromechanical actuation but fails at breakdown due to instability under certain conditions with a small deformation. By applying a mechanical pre-stretch, one obtains a stabilized large actuation. In this paper, we measured the dielectric constant and critical voltage of a polyacrylic dielectric elastomer subjected to both equal and unequal biaxial stretch, and modelled its actuation by employing the Gent strain energy function with a microscopic view to characterize the nonlinear stiffening behaviour and the electrostrictive effect in the deformation. The mechanical pre-stretch contributes in several ways to the stabilization of dielectric elastomer, by eliminating the pull-in instability, by generating electrostriction, by improving the breakdown strength, as well as by reducing the membrane thickness which consequently lowers the voltages required for activation.