Basics and Applications of Electrowetting on Dielectric (EW)

Dineshkumar Y. Turkar, Sandip M. Wadhai, Yogesh B. Sawane, Arun G. Banpurkar

Department of Physics, S P Pune University, Pune

The shape of liquid-droplet on planar surfaces is mainly governed by resultant surface tension forces at the vapour-liquid-solid boundary. In thermodynamic equilibrium, wetting of liquid or contact angle (CA) is given by Young-Dupr’e equation which is related to surface tensions of liquid, solid and interfacial tension of liquid-solid. The irreversible change in equilibrium wetting is possible by altering the surfaces and/or adding surfactant in the liquid. However, controlled and reversible wetting is desired in several applications like liquid-lens, ink-jet printing, droplet transport through micro-fluidic chip etc. Currently this is achieved by incident light, electric field, thermal gradient, magnetic field etc. The electric field induced wetting commonly termed as Electrowetting on dielectric (EWOD or EW) is the most successful method allowing fast and reversible change in wetting of aqueous and non aqueous droplet on dielectric surfaces. EW is currently implemented in variety of applications such as video displays, adaptive lens systems in cell-phone cameras, smart window panels etc. In the present review, we discuss basic EW phenomenon and governing equations. The experimental results related to EW based liquid lens system are discussed. The upcoming technology and challenges of EW are discussed at the end.