Separation technique of sub-micron particles using electrokinetically driven flow

An electrokinetic separation and/or filtering technique of charged order one-micron diameter particles in solution is demonstrated for further development of a multi-phase microfluidic device. Two buffered particle-laden streams of different ionic conductivities are introduced through a simple T-shaped microchannel. The fluid is driven by both pressure and a DC electric field. Upon application of an electric field, the particles are extracted from the lower conductivity stream and stacked into the higher conductivity stream. Both particle density imaging and quantiative velocity fields using micron resolution particle image velocimetry are presented in order to investigate the flow and electric fields. Numerical simulations of the process in the conductivity gradient show the generation of a transverse electric field, consequently force acting on particles is selectively controlled in a simple geometry microcannel.