Modeling of Oil/Water Interfacial Dynamics in Three-Dimensional Bistable Electrowetting Display Pixels

Electrowetting has drawn significant interest because of the potential applications of displays, lab-on-a-chip microfluidic devices, electro-optical switches, and so forth. However, electrowetting display (EWD) is monostable, which needs extra continuous voltage supply to keep contracting the oil. This paper is concerned with the simulation of two-phase liquid flow in three-dimensional EWD pixels with two electrodes (E1 and E2) demonstrating bistability, where power is only needed to move the oil droplet between two stable states. The effects of E1 geometry, E2 geometry, and E2 pulse characteristics on the dynamics of the oil droplet motion have been analyzed. Also, predictions of the transient states in four stages of the reversible bistable operation process have been carried out by employing the finite element method, in qualitative agreement with our experimental results of the monostable EWD and the existing literature. We seek to shed more light on the fundamental two-phase liquid flow in three-dimensional pixels exhibiting bistability for low power EWD and guide optimizing the electrodes to the perfect patterns with the aid of rigorous modeling.