Microfluidic concentration of sample solutes using Joule heating effects under a combined AC and DC electric field

Towards High Concentration Enhancement of Microfluidic Temperature Gradient Focusing of Sample Solutes

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 1 ◽

10.1115/icnmm2011-58273 ◽

2011 ◽

Author(s):

Zhengwei Ge ◽

Chun Yang

Keyword(s):

Temperature Gradient ◽

Electric Field ◽

Joule Heating ◽

Electroosmotic Flow ◽

High Concentration ◽

Temperature Gradient Focusing ◽

Heating Effects ◽

Concentration Enhancement ◽

Dc Electric Field ◽

High Frequency Ac

This paper reports an improved technique to enhance microfluidic temperature gradient focusing (TGF) of sample solutes using Joule heating effects induced by a combined AC and DC electric field. By introducing the AC field component, additional Joule heating effects are obtained to generate temperature gradient for concentrating sample solutes, while the electroosmotic flow is suppressed under the high frequency AC electric field. Therefore, the required DC voltages for achieving certain sample concentration by Joule heating induced TGF technique are remarkably reduced. Moreover, the lower DC voltages lead to smaller electroosmotic flow (EOF), thereby reducing the backpressure effects due to the finite reservoir size. Concentration enhancements of sample solutes are improved by using a combined AC and DC electric field.

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Microfluidics Concentration of Sample Solutes Using Joule Heating Effects Under Combined AC and DC Electric Field

ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels: Parts A and B ◽

10.1115/fedsm-icnmm2010-30451 ◽

2010 ◽

Author(s):

Zhengwei Ge ◽

Chun Yang

Keyword(s):

Temperature Gradient ◽

Electric Field ◽

Joule Heating ◽

Electroosmotic Flow ◽

Heating Effect ◽

Dc Voltage ◽

Joule Heating Effect ◽

Heating Effects ◽

Concentration Enhancement ◽

Dc Electric Field

Microfluidic concentration is achieved by utilizing Joule heating effect induced temperature gradient focusing (TGF) under a combined AC and DC electric field imposed in a straight microchannel with sudden expansion in cross-section. The introduction of AC electric field component services dual functions: one is to produce Joule heating effects for generating temperature gradient, and the other is to suppress electroosmotic flow with high frequencies. Therefore, the required DC voltage for achieving sample concentration with Joule heating induced TGF technique is remarkably reduced. The lower DC voltage can lead to smaller electroosmotic flow (EOF), thereby reducing the backpressure effect due to the finite reservoir size. It was demonstrated that using the proposed new TGF technique with Joule heating effect under a combined AC and DC field, more than 2500-fold concentration enhancement was obtained within 14 minutes in a PDMS/PDMS microdevice, which is an order of magnitude higher than the literature reported concentration enhancement achieved by microfluidic devices utilizing the Joule heating induced TGF technique.

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On Electrokinetic Mass Transport in a Microchannel With Joule Heating Effects

Journal of Heat Transfer ◽

10.1115/1.1865216 ◽

2005 ◽

Vol 127 (6) ◽

pp. 660-663 ◽

Cited By ~ 6

Author(s):

G. Y. Tang and ◽

C. Yang ◽

H. Q. Gong, ◽

C. J. Chai, and ◽

Y. C. Lam

Keyword(s):

Numerical Analysis ◽

Electric Field ◽

Mass Transport ◽

Joule Heating ◽

Model Development ◽

Finite Sample ◽

Order Accuracy ◽

Flat Interface ◽

Heating Effects ◽

Nicolson Scheme

This study presents a numerical analysis of electrokinetic mass transport in a microchannel with Joule heating effects. A nonuniform electric field caused by the presence of the Joule heating is considered in the model development. Numerical computations for electrokinetic mass transport under Joule heating effects are carried out using the Crank-Nicolson scheme of second-order accuracy in space and time for two different cases: (i) the translating interface and (ii) the dispersion of a finite sample plug. The simulations reveal that the presence of Joule heating not only causes the sample species to transport faster, but also causes the sample peak to decrease and the sample band to deviate from its flat interface or pluglike shape.

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