Abstract
Transient displacements of optically trapped particles in [NaCl] \(=\) 0.1 mM solutions produced by electroosmotic and electrophoretic forces at electric field start-up were profiled wall-to-wall through \(50\,\upmu \hbox {m}\) in a commercial microfluidic channel with a spatial resolution of \(1\,\upmu \hbox {m}\) and temporal resolution of 200 kHz. Data were inverted to compute the force on the particles and fitted to a first-principles finite element methods model to compute the flow profile, and zeta potential of the walls and particles. This analysis suggested that (1) electroosmotic flow in the channel was accompanied by a pressure gradient, producing backflow, and which was attributed to bubbles within the channel and that (2) while the zeta potential of the wall was broadly consistent with that expected, the zeta potentials across the nine particles examined was higher than might be expected, which were attributed to differences in surface conditions of the particular particles used.
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Data Availability Statement
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.
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Raudsepp, A., Hall, S.B. & Williams, M.A.K. Probing start-up electroosmotic forces and flows in a microfluidic channel using laser tweezer force spectroscopy. Microfluid Nanofluid 24, 87 (2020). https://doi.org/10.1007/s10404-020-02389-5
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DOI: https://doi.org/10.1007/s10404-020-02389-5