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Exploiting the Wall-Induced Non-inertial Lift in Electrokinetic Flow for a Continuous Particle Separation by Size

Lu, Xinyu, Hsu, Jyh-Ping, Xuan, Xiangchun
Langmuir 2015 v.31 no.1 pp. 620-627
dielectrophoresis, electric field, engineering, microparticles, models, polystyrenes
Separating particles from a heterogeneous mixture is important and necessary in many engineering and biomedical applications. Electrokinetic flow-based continuous particle separation has thus far been realized primarily by the use of particle dielectrophoresis induced in constricted and/or curved microchannels. We develop in this work a new electrokinetic method that exploits the wall-induced non-inertial lift in a straight uniform microchannel to continuously separate particles by intrinsic properties (e.g., size and surface charge). Such an electrically originated lift force arises from the asymmetric electric field distribution around a particle nearby a planar dielectric wall. We demonstrate this method through separating both a binary and ternary mixture of dispersed polystyrene microspheres by size in a T-shaped microchannel. A semi-analytical model is also developed to simulate and understand the particle separation process. The predicted particle trajectories in the entire microchannel agree reasonably well with the experimental measurements.