Surface roughness has been considered as a passive means of enhancing the species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of the 3D roughness and the surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional, finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. The results showed that, the rough channel’s geometry and the electroosmotic mobility ratio of the roughness elements’ surface to that of the substrate, εμ, have dramatic influence on the induced pressure field, the electroosmotic flow patterns and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample species transport in the heterogeneous rough microchannels presents tidal-wave-like concentration field at the intersection between four neighboring rough elements when under low εμ values, and presents the concentration field similar to that of the smooth channels when under high εμ values.

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