In this article, we demonstrate the determination of surface zeta potentials of composite microchannels using the electric-field-driven solution displacement method. Nonuniform surface charge creates linear electro-osmotic flow, which leads to asymmetric displacement. Simplified circuit models are derived to determine the surface zeta potentials through examining the behavior of transient currents during the displacement. The effects of dispersion on the measured zeta potentials are discussed in line with the flow characteristics under different surface charge conditions.
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