Dielectrowetting: The past, present and future

Liquid dielectrophoresis is a bulk force acting on dipoles within a dielectric liquid inside a non-uniform electric field. When the driving electrodes are interdigitated, bulk liquid dielectrophoresis is converted to an interface localised form capable of modifying the energy balance at an interface. When the interface is a solid-liquid one, the wetting properties of a surface are modified and this approach is known as dielectrowetting. Dielectrowetting has been shown to provide the ability to reversibly modify the contact angle of a liquid droplet with the application of voltage, the strength of which is controlled by the penetration depth of the non-uniform field and permittivities of the fluids involved. Importantly, dielectrowetting provides the ability to create thin liquid films, overcoming the limitation of contact angle saturation present in electrowerting. In this paper, we review the development of dielectrowetting - its origins, the statics and dynamics of dielectrowetted droplets, and the applications of dielectrowetting in microfluidics and optofluidics. Recent developments in the field are also reviewed showing the future directions of this rapidly developing field.