A study of AC electrokinetic phenomena under DC electroosmotic flows

AC electrokinetic phenomena have drawn much attention in the microfluidics and lab-on-a-chip communities since these techniques have a great potential for effective manipulation of small particles (micro- to nanoscale particles, polymer beads to biological cells and molecules) and fluids in microchannel environments. One unanswered question is how the AC electrokinetic phenomena are affected by DC electroosmotic flows that are often employed in lab-on-a-chip systems as a pumping method. This paper presents experimental and numerical studies on the interaction between AC electrokinetic phenomena and DC electroosmotic flows. The motions of polystyrene microbeads suspended in deionized water in a microchannel were studied as the main AC and DC electrokinetics parameters were varied. Numerical simulations of flow field were performed using COMSOL Multiphysics software. The forces considered in the numerical simulation include electrophoresis, DC electroosmosis, dielectrophoresis, AC electroosmosis, electrothermal effect, diffusion, Stokes drag force, and gravity. The numerical simulation results showed good agreements with experimental data. We believe that this study will contribute to the understanding of the interactions between DC and AC electrokinetic phenomena and thus enable researchers to develop powerful microdevices based on the combination of these two techniques.