MICRO-PIV measurements of induced-charge electro-osmotic flows

In this work, induced-charge electro-osmosis (ICEO) around single and multiple gold-coated stainless steel rod(s) was investigated. The rod(s) positioned at the center of a straight microchannel connecting two fluid reservoirs on either end. The microchannel was filled with pure and polymer-containing 1 mM KCl solution, which was seeded with 0.5 ?m diameter carboxylate-modified spherical particles. The ICEO flow around the metallic rod(s) was measured using the micro particle image velocimetry (micro-PIV) technique as functions of the AC electric field strength and frequency. The present study provides experimental data about the ICEO flow in the weakly nonlinear limit of thin double layers, in which the charging dynamics of the double layer cannot be presented analytically. Flow observed around the rod(s) was quadrupolar, which drived liquid towards the rod(s) along the electric field and forced it away from the rod(s) in the direction perpendicular to the imposed electric field. The measured ICEO flow velocity was proportional to the square of the electric field strength, depended on the applied AC frequency and polymer concentration.