Measurement of electroosmotic flow velocity and electric field in microchannels by micro-particle image velocimetry

Abstract

A method for measuring the distribution of electroosmotic flow velocity and electric field intensity in a microchannel by micro-particle image velocimetry (μPIV) is described. Two types of particles with differing electric surface properties were used as tracer particles in order to subtract the velocity component due to the effects of the electrophoretic force from the velocity of the particles. A calibration experiment was first carried out using a one-dimensional microchannel to obtain the correlation functions between the apparent electric field intensity and the velocity of the two particles. μPIV measurements were then carried out in the target microchannel to measure the electroosmotic flow and electric fields by using the same two tracer particles and the correlation function. To validate the present method, experiments were conducted for two types of microchannels. One was a straight channel that consisted of a material different from that used in the calibration, and the other was a corrugated channel. The results were compared with those of an experiment using fluorescent dye, as well as with numerical simulations. Good agreement was observed in both comparisons, affirming the validity of the proposed method.