Stretchable patterns on elastomeric substrates

Abstract

Compression-induced buckling instability of metal thin films on a compliant base result in surface wrinkles. A stiff thin film, perfectly bonded to an infinitely deep pre-stretched dielectric elastomer (DE) substrate, is considered. Linear perturbation analysis reveals the critical strain in the layer at the onset of wrinkling. A fully coupled Finite-Element (FE) scheme, based on large deformation electroelasticity, where domains of the mechanical and electrical problems coincide, is developed to model the elastomer. The procedure can handle nearly incompressible materials, which require careful considerations. The thin film is modeled as a beam. The numerical technique is used to study the post-buckling behavior upon relaxation of the pre-strained substrate. The FE domain is a unit cell of twice the characteristic wavelength. Assuming that there is no wrinkling-induced delamination at the film/substrate interface, the numerical analyses overview various tunable surface configurations distinctly different from the sinusoidal shape. The several topographic options broaden the functional horizon of surface instability patterns. Again, corrugation is essential to provide a degree of electrode compliance when the elastomer elongates in the lateral direction due to an applied electric potential. Simulations show the response of DE for the different surface profiles and also demonstrate the failure mechanisms that limit the actuation.