Electrowetting of sessile drops on soft dielectric elastomer films

Abstract

The interconnection between the variation of elasticity of a dielectric film and the wetting of a sessile drop on the same, under an applied electrical voltage, remains unclear. Here, we report the electrowetting-on-dielectric behaviour of sessile drops on films of varying elasticities, fabricated using a dielectric elastomer. Our results reveal that the elasticity of the dielectric elastomer film indeed provides an additional control over the droplet electrowetting behaviour. The extent of electrowetting reduces with decreasing elasticity of the dielectric elastomer film. This influence of the variation of the dielectric film elasticity on droplet electrowetting is best understood from free energy-based consideration, leading to a test of the applicability of the classical Lippmann–Young model. We also provide a description of the displacement profiles for the deformation of a soft dielectric film surface, due to the interfacial electro-elastocapillary interaction triggered by the electrowetted sessile droplet. The understandings developed here can be of profound importance in various emerging applications, ranging from the development of soft liquid lenses to controlled drug delivery.