Development of soft electromechanical materials is critical for several tantalizing applications such as human-like robots, stretchable electronics, actuators, energy harvesting, among others. Soft dielectrics can be easily deformed by an electric field through the so-called electrostatic Maxwell stress. The highly nonlinear coupling between the mechanical and electrical effects in soft dielectrics gives rise to a rich variety of instability and bifurcation behavior. Depending upon the context, instabilities can either be detrimental, or more intriguingly, exploited for enhanced multifunctional behavior. In this work, we revisit the instability and bifurcation behavior of a finite block made of a soft dielectric material that is simultaneously subjected to both mechanical and electrical stimuli. An excellent literature already exists that has addressed the same topic. However, barring a few exceptions, most works have focused on the consideration of homogeneous deformation and accordingly, relatively fewer insights are at hand regarding the compressive stress state. In our work, we allow for fairly general and inhomogeneous deformation modes and, in the case of a neo-Hookean material, present closed-form solutions to the instability and bifurcation behavior of soft dielectrics. Our results, in the asymptotic limit of large aspect ratio, agree well with Euler's prediction for the buckling of a slender block and, furthermore, in the limit of zero aspect ratio are the same as Biot's critical strain of surface instability of a compressed homogeneous half-space of a neo-Hookean material. A key physical insight that emerges from our analysis is that soft dielectrics can be used as actuators within an expanded range of electric field than hitherto believed.

In this work, we analyze nonlinear bending deformation of a soft electret structure and examine the precise conditions that may lead to a strong emergent piezoelectric or flexoelectric response under bending.

Can the mere crumpling of a "paper" produce electricity? An inhomogeneous strain can induce electrical response in all dielectrics and not just piezoelectric materials. This phenomenon of flexoelectricity is rather modest unless unusually large strain gradients are present. In this work, we analyze the crumpling of thin elastic sheets and establish scaling laws for their electromechanical behavior to prove that an extremely strong flexoelectric response is achieved at sub-micron length-scales. Connecting with recent experiments on crumpling of a polymer paper, we argue that crumpling is a viable energy harvesting route with applications in wearable electronics and related contexts.

Magnetoelectric materials that convert magnetic fields into electricity and vice versa are rare and usually complex, hard crystalline alloys. Recent work has shown that soft, highly deformable magnetoelectric materials may be created by using a strain-mediated mechanism. The electromagnetic and elastic deformation of such materials is intricately coupled, giving rise to a rather rich instability and bifurcation behavior that may limit or otherwise put bounds on the emergent magnetoelectric behavior. In this work, we investigate the magneto-electro-mechanical instability of a soft dielectric film subject to mechanical forces and external electric and magnetic fields. We explore the interplay between mechanical strain, electric voltage and magnetic fields and their impact on the maximum voltage and the stretch the dielectric material can reach. Specifically, we present physical insights to support the prospects to achieve wireless energy harvesting through remotely applied magnetic fields.

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