Electrowetting-on-dielectric-induced nanodroplet splitting between two parallel plates

Abstract

Manipulation of nano/microdroplets has recently received a great deal of attention because of its promising applications. In this study, electrowetting-on-dielectric (EWOD)-induced nanodroplet splitting between two parallel plates is investigated via molecular dynamics (MD) simulations. The results show that the splitting and non-splitting dynamics closely depend on the charge density applied to electrodes. There exists a critical charge density, above which successful splitting is observed. The plate gap and electrode size are found to significantly influence the critical charge density. Furthermore, MD simulations also demonstrate that the criterion of splitting for millimeter-sized droplets fails to predict nanodroplet splitting. On the basis of two simple geometric relations between the droplet and electrode sizes, a new criterion, 1/2 ≤ R0/l ≤ (3/π − 1/4)1/2, is proposed to estimate whether nanodroplets can be split, where R0 is the initial wetting radius of nanodroplets on the plates when no charge is applied to electrodes, and l is the electrode size. The proposed criterion is in good agreement with MD simulations.