Reversible Electrowetting on Dual-Scale-Patterned Corrugated Microstructured Surfaces

The ability to reversibly switch between a hydrophobic Cassie state and a hydrophilic Wenzel state is often not possible on textured surfaces because of energy barriers which result from the geometry of the microstructure. In this paper, we report on a simple microstructure geometry that allows an aqueous droplet to be reversibly switched between these states by the application of electrowetting. We demonstrate reversible electrowetting in air on microstructured surfaces consisting of parallel corrugations and show that this geometry can be engineered to produce a Cassie state and can be electrically controlled to switch to a Wenzel wetting state having high adhesion. When the electric field was removed, we observed spontaneous dewetting along the corrugations as the droplet transitioned from the Wenzel state back to a Cassie state.