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Issue 8, 2006
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High-efficiency electrokinetic micromixing through symmetric sequential injection and expansion

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Abstract

Rapid electric field switching is an established microfluidic mixing strategy for electrokinetic flows. Many such microfluidic mixers are variations on the T- or Y-form channel geometry. In these configurations, rapid switching of the electric field can greatly improve initial mixing over that achieved with static-field mixing. Due to a fundamental lack of symmetry, however, these strategies produce lingering cross-channel concentration gradients which delay complete mixing of the fluid stream. In this paper, a field switching microfluidic mixing strategy which utilizes a symmetric sequential injection geometry with an expansion chamber to achieve high efficiency microfluidic mixing is demonstrated experimentally. A three-inlet injector sequentially interlaces two dissimilar incoming solutions. Downstream of the injector, the sequence enters an expansion chamber resulting in a dramatic (two orders of magnitude) decrease in Peclet number and rapid axial diffusive mixing. The outlet concentration may be accurately varied over the full spectrum by tuning the duty cycle of the field switching waveform. The chips are designed with input from a previous numerical study, manufactured in poly(dimethylsiloxane) using soft-lithography based microfabrication, and tested using fluorescence microscopy. In the context of on-chip chemical processing for analytical operations, the demonstrated mixing strategy has several features: high mixing efficiency (99%), compact axial length (2.3 mm), steady outflow velocity, and readily variable outlet concentration (0.15 < c* < 0.95).

Graphical abstract: High-efficiency electrokinetic micromixing through symmetric sequential injection and expansion

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Publication details

The article was received on 13 Feb 2006, accepted on 26 May 2006 and first published on 14 Jun 2006


Article type: Paper
DOI: 10.1039/B602085B
Citation: Lab Chip, 2006,6, 1033-1039
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    High-efficiency electrokinetic micromixing through symmetric sequential injection and expansion

    J. T. Coleman, J. McKechnie and D. Sinton, Lab Chip, 2006, 6, 1033
    DOI: 10.1039/B602085B

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