In this work, we found experimentally that there exist fairly strong fluid flows in AC electrowetting, which can be utilized as a means to mix the fluids in EWOD-based micro-devices. We visualized the internal flow. There may exist two distinct flow-generation mechanisms; one is the droplet oscillation, and the other is the electrohydrodynamic flow. The flow pattern is significantly dependent on the applied AC frequency. At low frequencies (represented here by 1 kHz), the center of the vortices is located somewhat randomly and the flow directs upward near the symmetric axis. At high frequencies (represented by 128 kHz), however, a pair of vortices having quite a regular structure is clearly visible and the flow directs downward near the symmetric axis. The flow patterns are strongly dependent on the position of the point electrode. The droplet surface undergoes a periodic oscillation (visualized by a high-speed camera) with a frequency exactly twice the frequency of applied electrical signal. The oscillating interface can generate a steady streaming. However the numerical results show that there exists no electric field at low AC frequencies. On the contrary, there exists quite a strong electric field inside the droplet at high frequencies. It means the electrohydrodynamic flow cannot be generated at the low frequency region, and the droplet oscillation might cause the flow generation at low frequencies. We also demonstrated the flow can be beneficially utilized as a mixing method.
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ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer
June 6–9, 2008
Tainan, Taiwan
Conference Sponsors:
- Nanotechnology Institute
ISBN:
0-7918-4292-4
PROCEEDINGS PAPER
Hydrodynamic Flows in Electrowetting Available to Purchase
Sung Hee Ko,
Sung Hee Ko
Pohang University of Science and Technology, Pohang, South Korea
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Horim Lee,
Horim Lee
Pohang University of Science and Technology, Pohang, South Korea
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Kwan Hyoung Kang
Kwan Hyoung Kang
Pohang University of Science and Technology, Pohang, South Korea
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Sung Hee Ko
Pohang University of Science and Technology, Pohang, South Korea
Horim Lee
Pohang University of Science and Technology, Pohang, South Korea
Kwan Hyoung Kang
Pohang University of Science and Technology, Pohang, South Korea
Paper No:
MNHT2008-52059, pp. 109-112; 4 pages
Published Online:
June 22, 2009
Citation
Ko, SH, Lee, H, & Kang, KH. "Hydrodynamic Flows in Electrowetting." Proceedings of the ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer, Parts A and B. Tainan, Taiwan. June 6–9, 2008. pp. 109-112. ASME. https://doi.org/10.1115/MNHT2008-52059
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