Nonlinear electrokinetic phenomena around nearly insulated sharp tips in microflows

Yuval Eckstein, Gilad Yossifon, Avraham Seifert, Touvia Miloh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

This contribution seeks to provide for the first time a combined comprehensive theoretical prediction and quantitative experimental (microparticle imaging velocimetry - μ-PIV) measurements of the nonlinear electrokinetic flow around sharp tips in order to substantiate former theoretical and qualitative experimental flow visualization results [S.K. Thamida, H.C Chang, Phys. Fluids 14 (2002) 12; P. Takhistov, K. Duginova, H.C. Chang, J. Colloid Interface Sci. 263 (2003) 133; G. Yossifon, I. Frankel, T. Miloh, Phys. Fluids 18 (2006) 117108]. The study focuses on two microchannel designs: an L-shaped channel and two isolated tips in a straight channel, important in engineering for mixing and particle-trapping purposes. The new experimental results were explained in terms of an induced-charge electrokinetic mechanism alone, without the concentration polarization mechanism as suggested by earlier studies. The vortex generation phenomenon around corners was explained in terms of the varying ratio between the equilibrium and the induced-charge zeta-potentials, showing fair qualitative agreement between numerical and experimental results. Hence, a transition from an irrotational to nonlinear-dominated flow with a vortex pattern occurs beyond a certain electric-field threshold. In particular, for the L-shaped channel case, it is demonstrated that beyond a second field threshold an upstream vortex appears in addition to the downstream one.

Original languageEnglish
Pages (from-to)243-249
Number of pages7
JournalJournal of Colloid and Interface Science
Volume338
Issue number1
DOIs
StatePublished - 1 Oct 2009

Keywords

  • Electrokinetic flow
  • Induced-charge electroosmosis
  • Microfluidics
  • Polarization
  • Sharp tip
  • Vortex

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