Enhanced particle trapping performance of induced charge electroosmosis

Abstract

By increasing the number of floating electrodes or enlarging the width of single floating electrode, this work provides effective ways to strongly improve the particle trapping performance of induced charge electroosmosis (ICEO). Particle trapping with double or triple separate narrow floating electrodes increases the effective actuating range of ICEO flow and therefore enhance the optimum trapping ability to be 1.63 or 2.34 times of that with single narrow electrode (width of L=200μm), and the ideal trapping frequency is independent of the electrode number due to the mutual independence of electrochemical ion relaxation over each electrode. Furthermore, using a single wide floating electrode with the effective width equal to three separate narrow floating electrodes (L=600μm) instead of a single narrow one slightly lowers the ideal trapping frequency due to an increase in the characteristic polarization length, but the trapping performance is only up to 1.59 times of that with original single narrow electrode, implying that vertical channel confinement effect may severely suppresses the effective actuating range of ICEO flow and renders the trapping performance not as expected. Trapping experiments over wide floating electrode with different channel height were carried out, showing that the trapping performance increases by correctly increasing the channel height.

Keywords: Enhanced particle trapping; Induced charge electroosmosis; Microfluidics; Multiple floating electrodes.