Micromixing of pressure driven flow and surface induced charge coupling in a serpentine microchannel: A numerical study

The addition of surface induced charge to generate vortices in the pressure driven flow (PDF)-dominated serpentine microchannels can enhance the mixing quality within different Reynolds numbers (Re) range. In this work, a numerical study is conducted to examine the effects of operational and geometric parameters of the conductive plate on the hydraulic and mixing performance in the serpentine square wave channels when 0.01 ≤Re≤ 5. The findings indicate that for 0.01 ≤Re≤ 0.1, the PDF exhibits significant difficulties in suppressing the sliding velocity of the plate surface, resulting in the fully developed vortex structures and a mixing index predominantly above 0.8 and 0.9. For 0.1＜Re≤ 1 conditions, the compression of the PDF causes the vortex pairs to separate and degenerate on the plate surface, with a significant decrease in the mixing index observed. Notably, the implementation of a rotating conductive plate can effectively enlarge the polarization area, which augments the peak zeta potential and elevates the slip velocity on the plate surface, thereby intensifying vortices. Moreover, the conductive plate positioned within the curved channel can leverage the centrifugal effect of the stretched induced vortex pairs to enhance the extrusion effect on the working medium and shorten the mass transfer distance. Based on optimized plate parameters, the integration of a rotating array along the microchannel is proposed to effectively enhance mixing quality. However, these beneficial behaviors that enhance mixing contribute to an increase in local pressure loss. For 1＜Re≤ 5 conditions, the PDF gradually assumes primacy in the mixing process, rendering the vortex structures induced by the conductive plate ineffective. This research offers novel perspectives on micromixing under the combined influence of PDF and induced charge.