Evaluation of electroosmotic velocity and zeta-potential in microchannel using submicron fluorescent particles

Abstract

Measurements of electrophoretic and electroosmotic velocities were performed by using micron-resolution particle image velocimetry (micro-PIV) and submicron fluorescent particles. Electrophoretic velocity of particles was obtained by micro-PIV measurement in a closed cell, while electroosmotic velocity of buffer solution in a microchannel was calculated by subtracting electrophoretic verocity from observed velocity measured by micro-PIV. Both zeta-potential of particles and microchannel wall were obtained by using electrophoretic and electroosmotic velocities, respectively, which are increased with increasing pH of buffer solution, due to deprotonation. Transient process of zeta-potential at the wall surface in a T-shaped microchannel was detected by spatially-averaged electroosmotic velocities.