The dewetting of a nanoscale water film under the action of an electric field is studied with molecular dynamics simulation. Results show that the onset of film rupture is induced by a spontaneous instability mechanism. After the rupture, the rim of the film recedes with a dynamic contact angle. The transient streamlines at a typical moment show that the liquid molecule near the rim moves almost vertically upwards, driven by the repulsive force from the solid surface. The oscillatory behavior of the density profile, resulting from the interaction between attractive and repulsive potentials, is observed near the solid surface. The analyses of the dewetting process demonstrate that the applied electric field will increase the wettability of graphite walls, thus suppressing the rupture, reducing the dynamic contact angle, and raising the liquid density adjacent to both the solid and liquid-vacuum surfaces. Owing to the polarity of water, the positive voltage produces stronger influences than the negative one.

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A mesoscopic model is developed to investigate the oscillations of a sub-micrometer droplet in AC electrowetting based on dissipative particle dynamics. To simulate the effects of the applied AC voltage, we vary the interaction between the solid and liquid particles aiming to recover the contact angles obeying the Lippmann-Young equation. The low frequency flow obtained in the present study is consistent qualitatively with previous experimental measurement. For the intermediate frequency voltage, generally no significant movement is found inside the droplet except fluid oscillatory motion near the contact line. The contact line dynamics is investigated as well, in which the results show the hysteresis phenomenon of contact line movement, and the phase difference between the applied voltage variation and the contact line oscillation generally increases with the AC frequency except for some resonance frequencies. Furthermore, the amplitude of the contact line is found to decrease linearly on a logarithmic scale with the applied frequency.