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Microfluidic flow reversal at low frequency by AC electrothermal effect

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Abstract

This paper describes a flow reversal phenomenon for fluids with moderate conductivity. Fluids with conductivities of 2 × 10−4 S/m, 0.02 S/m and up to 0.1 S/m were experimented at frequencies ranging from 1 to 110 kHz. Flow reversal was observed only at ~1 kHz and 5.3 V rms for σ = 0.02 S/m, and our analysis indicates that AC electrothermal effect could be responsible. Analysis of the system impedance and simulation of power consumption show that the distribution of electric power consumption is dependent on conductivity and AC frequency. At low frequencies, possibly more electric power is consumed at surface/electrolyte interface rather than within the fluid, which consequently changes the location of temperature maximum and the directions of temperature gradients. The direction of AC electrothermal force is reoriented, causing the flow reversal. Numerical simulation is also performed and agrees within the experiments.

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Acknowledgment

The project has been supported by the US National Science Foundation under grant number ECS-0448896.

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Authors and Affiliations

  1. Department of Electrical Engineering and Computer Science, The University of Tennessee, Knoxville, TN, 37996, USA

    Meng Lian & Jie Wu

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  1. Meng Lian
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  2. Jie Wu
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Correspondence to Jie Wu.

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Lian, M., Wu, J. Microfluidic flow reversal at low frequency by AC electrothermal effect. Microfluid Nanofluid 7, 757 (2009). https://doi.org/10.1007/s10404-009-0433-6

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  • DOI: https://doi.org/10.1007/s10404-009-0433-6

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