Electrode Cooling Effect on Out-Of-Phase Electrothermal Streaming in Rotating Electric Fields
1
School of Electronics and Control Engineering, Chang’an University, Middle-Section of Nan’er Huan Road, Xi’an 710064, China
2
School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China
3
State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China
*
Authors to whom correspondence should be addressed.
Micromachines 2017, 8(11), 327; https://doi.org/10.3390/mi8110327
Received: 23 September 2017
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Revised: 3 November 2017
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Accepted: 4 November 2017
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Published: 6 November 2017
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)
In this work, we focus on investigating electrothermal flow in rotating electric fields (ROT-ETF), with primary attention paid to the horizontal traveling-wave electrothermal (TWET) vortex induced at the center of the electric field. The frequency-dependent flow profiles in the microdevice are analyzed using different heat transfer models. Accordingly, we address in particular the importance of electrode cooling in ROT-ETF as metal electrodes of high thermal conductivity, while substrate material of low heat dissipation capability is employed to develop such microfluidic chips. Under this circumstance, cooling of electrode array due to external natural convection on millimeter-scale electrode pads for external wire connection occurs and makes the internal temperature maxima shift from the electrode plane to a bit of distance right above the cross-shaped interelectrode gaps, giving rise to reversal of flow rotation from a typical repulsion-type to attraction-type induction vortex, which is in good accordance with our experimental observations of co-field TWET streaming at frequencies in the order of reciprocal charge relaxation time of the bulk fluid. These results point out a way to make a correct interpretation of out-of-phase electrothermal streaming behavior, which holds great potential for handing high-conductivity analytes in modern microfluidic systems.
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Keywords:
electrothermal flow; rotating electric field; out-of-phase smeared structural polarization; electrode cooling; external natural convection; co-field flow rotation
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MDPI and ACS Style
Liu, W.; Ren, Y.; Tao, Y.; Chen, X.; Wu, Q. Electrode Cooling Effect on Out-Of-Phase Electrothermal Streaming in Rotating Electric Fields. Micromachines 2017, 8, 327. https://doi.org/10.3390/mi8110327
AMA Style
Liu W, Ren Y, Tao Y, Chen X, Wu Q. Electrode Cooling Effect on Out-Of-Phase Electrothermal Streaming in Rotating Electric Fields. Micromachines. 2017; 8(11):327. https://doi.org/10.3390/mi8110327
Chicago/Turabian StyleLiu, Weiyu, Yukun Ren, Ye Tao, Xiaoming Chen, and Qisheng Wu. 2017. "Electrode Cooling Effect on Out-Of-Phase Electrothermal Streaming in Rotating Electric Fields" Micromachines 8, no. 11: 327. https://doi.org/10.3390/mi8110327
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