Enhancement of Dielectrophoretic Forces by Changing Microchannel Geometry

Abstract

We study the effects of microchannel geometry on a particle flow driven by electrokinesis and dielectrophoresis for rapid sample separation. The microchannel has electrically insulating circular posts which generate electric field gradient for dielectrophoresis. An in-house numerical code is developed using a model reported in the literature [1] to predict particle flows. The numerical code is validated by comparing the results of the present study to those in the literature. Also, a Monte-Carlo simulation is conducted to visualize the three particle flows. The results show that the dielectrophoretic force exerted on particles becomes strongest when the longitudinal spacing between neighboring posts is 0.6 times the post radius, regardless of other geometric parameters. Based on the results, we propose a microchannel geometry suitable for rapid particle separation that is often required for on-chip sample pretreatment. The results of numerical simulations confirm that there are three particle-flow types when the particle flow is driven by electrokinesis and dielectrophoresis flow: electrokinetic flow, streaming dielectrophoretic flow, and trapping dielectrophoretic flow. In addition, we discuss the critical values of dimensionless variables that distinguish the three particle flow types.