The renaissance of electrowetting

Control of wetting on conducting surfaces using external stimuli such as electricity, underlies the operation of devices in a broad range of technologies including micro-/nano-fluidics, energy conversion/storage and filtration systems. Electrowetting is the change in contact angle of a liquid relative to its equilibrium value upon application of a potential bias. The phenomenon, being identified almost a century ago, is fundamentally an electrochemical process. However, the majority of the most recent research in this area focuses on electrowetting from the "applications" perspective. Device-based electrowetting uses substrates with insulating overlayers to eliminate charge transfer at the solid|liquid interface and hence suppress the electrochemical character of the overall process. In this short review, we focus on electrowetting directly on conductors and discuss the purely electrochemical aspects of the phenomenon along with the open questions related to this rejuvenated topic.