Evoking or suppressing electromechanical instabilities in soft dielectrics with deformation-dependent dielectric permittivity

Abstract

Soft dielectric films subjected to the electromechanical loads can easily have large deformations that are accompanied by a variety of failure modes. The functions of soft dielectric actuators and harvesters are limited due to the existence of electromechanical instabilities. In this paper, we study the large deformation and electromechanical instabilities of a soft dielectric film by prescribing its deformation in one direction. The prescribed deformation can enhance the film stability; even more, it can avoid pull-in instability in dielectric films with constant dielectric permittivity. However, the prescribed stretch would bring another failure mode, i.e., loss of tension, in the prescribed direction. So far, the co-existence of pull-in instability and loss of tension is seldom reported in dielectric films with a prescribed deformation. We find that the deformation-dependent dielectric permittivity has a considerable impact on electromechanical behaviors. The competition between pull-in instability and loss of tension exists in dielectric films with a permittivity that increases with deformation. Our stability analyses find the conditions under which the deformation-dependent dielectric permittivity evokes pull-in instability or suppresses loss of tension.