Electro-osmotic flow (EOF) in microchannels is restricted to low Reynolds number regimes. Since the inertia forces are extremely weak in such regimes, turbulent conditions do not readily develop. Therefore, species mixing occurs primarily by diffusion, with the result that extended mixing channels are generally required. In this paper we present an investigation to predict the optimal applied voltage for the side channel type micromixer (SCTM) which is capable of continuous sample mixing for microfluidic applications. The device uses electrokinetical focusing which is an important EOF phenomenon. In this study, according to the conservation of mass, a simple theoretical model, based on the ‘flow-rate-ratio’ model and Kirchhoff’s law, is first proposed to predict the performance of the device. Computational fluid dynamics simulations are performed to investigate the effect of this model on the mixing efficiency. The results reveal that the mixing efficiency can be enhanced by using ‘flow-rate-ratio’ model and Kirchhoff’s law to predict the optimal applied voltage.

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