Dissipative Particle Dynamics Simulation of Droplet Oscillations in AC Electrowetting

Abstract

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.

Keywords:

• Dissipative particle dynamics
• AC electrowetting
• droplet
• oscillation
• flow field
• contact line

Acknowledgements

This work was supported by the National Science Foundation of China (Grant Nos 10872122, 10772107), Shanghai Fundamental Research Foundation (Grant No. 08JC1409800), Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0844), and Shanghai Program for Innovative Research Team in Universities.