Effective and versatile microfluidic pumps can be designed by utilizing various electrokinetic effects, such as electrohydrodynamics (EHD), induced-charge electroosmosis (ICEO) and dielectrophoresis (DEP). Among these, traveling-wave EHD (twEHD) has emerged as a powerful pumping mechanism due to its potential for miniaturization and the ability to pump a variety of liquids. However, when twEHD is used to deliver colloidal suspensions, the simultaneous presence of traveling-wave DEP (twDEP) effect may favorably or adversely influence the overall pumping performance, depending on the particle-fluid combination and the frequency range of the applied electric field. In this paper, the coupled EHD and DEP flows were studied numerically in a microchannel with a three-phase interdigitated microelectrode array fabricated at the bottom surface. In the numerical model, the particle-fluid interaction due to twDEP was solved using an equivalent mixture model, and the resultant velocity field was compared to that induced by either the repulsion type or the attraction type of EHD. The results show, depending on the frequency range of the traveling wave electric field and the applied thermal boundary condition, the EHD-induced flow can significantly enhance or weaken the twDEP-induced flow, vice versa.

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