The time variation of the shape of a perfectly conducting droplet placed between two orthogonal pairs of parallel electrodes with two-phase voltage excitation demonstrates that a water droplet vibrates strongly at certain frequencies. It was found that the resonance frequency and the magnitude of the deformation strongly depend on the surface properties.
This paper also presents a new design of an electrowetting mixer using the rotating electric field and offers a new method to effectively mix two droplets over a different range of AC frequencies. Two regimes were observed for droplet coalescence: (1) coalescence due to the high droplet deformation, (2) coalescence due to the interaction of electrically induced dipoles. Numerical simulations confirm that by increasing the electric capillary number, the first coalescence regime starts at lower frequencies.