Numerical analysis of finite Debye-length effects in induced-charge electro-osmosis

Misha Marie Gregersen, Mathias Bækbo Andersen, G. Soni, C. Meinhart, Henrik Bruus

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    Abstract

    For a microchamber filled with a binary electrolyte and containing a flat unbiased center electrode at one wall, we employ three numerical models to study the strength of the resulting induced-charge electro-osmotic (ICEO) flow rolls: (i) a full nonlinear continuum model resolving the double layer, (ii) a linear slip-velocity model not resolving the double layer and without tangential charge transport inside this layer, and (iii) a nonlinear slip-velocity model extending the linear model by including the tangential charge transport inside the double layer. We show that, compared to the full model, the slip-velocity models significantly overestimate the ICEO flow. This provides a partial explanation of the quantitative discrepancy between observed and calculated ICEO velocities reported in the literature. The discrepancy increases significantly for increasing Debye length relative to the electrode size, i.e., for nanofluidic systems. However, even for electrode dimensions in the micrometer range, the discrepancies in velocity due to the finite Debye length can be more than 10% for an electrode of zero height and more than 100% for electrode heights comparable to the Debye length.
    Original languageEnglish
    JournalPhysical Review E
    Volume79
    Issue number6
    Pages (from-to)066316
    ISSN2470-0045
    DOIs
    Publication statusPublished - 2009

    Bibliographical note

    Copyright 2009 American Physical Society

    Keywords

    • osmosis
    • microfluidics
    • slip flow
    • electrophoresis
    • nanofluidics
    • electrolytes
    • flow simulation

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