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Issue 3, 2004
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Dielectric spectroscopy in a micromachined flow cytometer: theoretical and practical considerations

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Abstract

We propose a model to determine the influence of different cell properties, such as size, membrane capacitance and cytoplasm conductivity, on the impedance spectrum as measured in a microfabricated cytometer. A dielectric sphere of equivalent complex permittivity is used as a simplified model to describe a biological cell. The measurement takes place between a pair of facing microelectrodes in a microchannel filled with a saline solution. The model incorporates various cell parameters, such as dielectric properties, size and position in the channel. A 3D finite element model is used to evaluate the magnitude of the electric field in the channel and the resultant changes in charge densities at the measurement electrode boundaries as a cell flows past. The charge density is integrated on the electrode surface to determine the displacement current and the channel impedance for the computed frequency range. The complete impedance model combines the finite element model, the electrode–electrolyte interface impedance and stray impedance, which are measured from a real device. The modeled dielectric complex spectra for various cell parameters are discussed and a measurement strategy for cell discrimination with such a system is proposed. We finally discuss the amount of noise and measurement fluctuations of the sensor.

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Publication details

The article was received on 30 Oct 2003, accepted on 22 Dec 2003 and first published on 25 Feb 2004


Article type: Paper
DOI: 10.1039/B313761A
Citation: Lab Chip, 2004,4, 241-251
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    Dielectric spectroscopy in a micromachined flow cytometer: theoretical and practical considerations

    S. Gawad, K. Cheung, U. Seger, A. Bertsch and P. Renaud, Lab Chip, 2004, 4, 241
    DOI: 10.1039/B313761A

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