This paper addresses the effects of microchannel geometry with electrically insulating posts on a particle flow driven by electrokinesis and dielectrophoresis. An in-house numerical program is developed using a numerical model proposed in literature to predict particle flows in a microchannel with a circular post array. The numerical program is validated by comparing the results of the present study to those in the literature. Results obtained from a Monte-Carlo simulation confirm the three particle flow types driven by an external DC electric field: electrokinetic flow, streaming dielectrophoretic flow, and trapping dielectrophoretic flow. In addition, we study the effects of electrokinetic and dielectrophoretic forces on particle transports by introducing a ratio of lateral to longitudinal forces exerted on a particle. As a result, we propose an improved microchannel geometry to enhance particle transports across electrokinetic streamlines for a given power dissipation. The improved microchannel has a shorter longitudinal spacing between the circular posts than a reference microchannel. We also discuss the critical values of dimensionless variables that distinguish the three particle flow types for both improved and reference microchannels.
This article presents a new method that overcomes three-dimensional effects by using twodimensional computational fluid dynamics (CFD) and response surface methodology (RSM). The method is applied to shape optimization of cutoff. The distributions of velocity and pressure obtained by two-dimensional CFD analysis are compared with those of threedimensional CFD analysis and experimental results. RSM with central composite designs is used to obtain an approximated volume flow rate in terms of the angle and curvature radius of cutoff. The optimal angle and radius of cutoff are determined as 72.4 and 0.092 times the outer diameter of the impeller, respectively.
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