Microtech 2011

Experimentally-validated theory for the effective zeta potential in microchannel with gate electrodes

F. Bonotto, A. Lenzi, F. Viola, M. Napoli, J. Frey, S. Pennathur
University of California, Santa Barbara, US

Keywords: zeta potential, flow control, gate electrodes, microchannel


In this work we develop an approach to solve for the effective zeta potential in a channel with nonuniform zeta potentials, such as metal gate electrodes in the channel network for flow control applications. Specifically, we present a robust numerical method to simulate a current monitoring experiment in a channel with a gate electrode changing the zeta potential at one surface of the channel. We use our model to accurately predict the effective zeta potential for a nonhomogenous channel for any displacement buffer concentration ratio and any value of the externally applied axial electric field, and show conditions where effective zeta potential are not accurate, as well as how to account for such inaccuracies in measurement, in order to recover the correct effective zeta potential from current monitoring measurements. Finally, as a robust validation of our theoretical method, we perform experiments of our model on a silica-PMDS microchannel system with a nonuniform zeta potential in the form of a gate electrode that covers 50% of the channel in on the silica surface. We show that this method accurate predicts the effective zeta potential using a model for gate electrodes.

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