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SPECIAL SECTION ON THE FLUID MECHANICS AND RHEOLOGY OF NONLINEAR MATERIALS AT THE MACRO, MICRO AND NANO SCALE

Surface Micromachined Dielectrophoretic Gates for the Front-End Device of a Biodetection System

[+] Author and Article Information
Conrad D. James

 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185cdjame@sandia.gov

Murat Okandan

 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185mokanda@sandia.gov

Paul Galambos

 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185pcgalam@sandia.gov

Seethambal S. Mani

 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185ssmani@sandia.gov

Dawn Bennett

 The University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250dawnb@umbc.edu

Boris Khusid

New Jersey Institute of Technology, University Heights, Newark, NJ 07102khusid@adm.njit.edu

Andreas Acrivos

The Levich Institute, The City College of New York, 140th Street & Convent Avenue, New York, NY 10031acrivos@scisun.sci.ccny.cuny.edu

J. Fluids Eng 128(1), 14-19 (Apr 21, 2005) (6 pages) doi:10.1115/1.2136924 History: Received July 20, 2004; Revised April 21, 2005

We present a novel separation device for the front-end of a biodetection system to discriminate between biological and non-biological analytes captured in air samples. By combining AC dielectrophoresis along the flow streamlines and a field-induced phase-separation, the device utilizes “dielectrophoretic gating”to separate analytes suspended in a flowing fluid based on their intrinsic polarizability properties. The gates are integrated into batch fabricated self-sealed surface-micromachined fluid channels. We demonstrate that setting the gate to a moderate voltage in the radio frequency range removed bacteria cells from a mixture containing non-biological particles without the need for fluorescent labeling or antibody-antigen hybridization, and also validate experimentally basic relations for estimating the gate performance.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Proposed biodetection system that uses dielectrophoretic gates as a trigger/cue to signal the detection of an unknown biological analyte, and to separate biological from non-biological materials

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Figure 2

(a) Schematic of a dielectrophoretic gate consisting of two electrodes arranged perpendicular to the fluid flow. (b) Log plot of the simulated ∇Erms2(x,z) for the two-electrode dielectrophoretic gate. Electrodes (black rectangles) are added for clarity. Dimensions are in μm.

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Figure 3

(a) SwIFT™ film stack with five polysilicon, three silicon nitride, and four sacrificial silicon oxide layers. (b) Scanning electron micrograph of a series of dielectrophoretic gates. The fluid channel sidewalls are denoted by the white arrows. Scale bar=30μm.

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Figure 4

(a) At 10V pp, 15MHz, bacteria adhere to the gate, while latex particles are repulsed and form a front (dashed line). Fluid velocity, 5–10μm∕s. Scale bar=20μm. (b) DEP-induced velocity of bacteria (n=3) and latex particles (n=4) at 15MHz as a function of distance from the center of the gate.

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Figure 5

Approximately 0.5s after the frequency is switched from 15MHzto100kHz, latex particles are traversing the gate along the sidewalls, while bacteria remain trapped. All accumulated latex particles escape the gate within 5s following the frequency shift.

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