Particle Accumulation by AC Electroosmosis in Microfluidic Device with Co-Planar Electrodes

Abstract

This paper reports a particle accumulation driven by alternating-current electroosmosis (ACEO) in a microfluidic device with co-planar electrode. Accumulation processes of particles in single- and double-gap electrode device were investigated. The flow field of ACEO and flow-induced particle accumulation process were measured by the micron-resolution particle tracking velocimetry and fluorescent intensity analysis, respectively. Particles in a solution are concentrated gradually from an electrode edge close to gap at the entrance and converged into a certain location downstream. Contribution of ACEO to particle transportation and eventual accumulation was discussed, and dependences of experimental parameters on the accumulating position were evaluated as well. The particle concentration behavior can be classified into two types; one has similar accumulating characteristics in both gap patterns, the other is the case in which particles are concentrated at the center span of the channel. Consequently, it is indicated from the results in this study that an estimation of the particle concentration is possible in a device with more complicated electrode geometry based on that in the single-gap device. The particle focusing method by ACEO can contribute to an improvement of detection sensitivity in the microfluidic system.