Process intensification of particle separation by lift force in arc microchannel with bifurcation

The present study demonstrates a novel hydrodynamic lift force sieving attained in an arc microchannel with a bifurcation at the downstream end. The fluorescent polystyrene particles with diameter of 10 or 20 μm are dispersed in water or NaCl aqueous solutions so that the particles are completely neutrally buoyant, lighter or denser relative to medium. The slurry is fed into the arc microchannel whose radius, width and depth are 20 mm, 200 and 150 μm, respectively. The fluorescent trajectories of flowing particles are recorded at the bifurcation. It is found that the 20-μm particle is sharply focused to an equilibrium position somewhat distant from the outer wall regardless of the given density difference. As a result, all 20-μm particles report to the outer branch of bifurcation. On the other hand, the 10-μm particles dispersed mostly across the channel width are always recovered from the both branches. The results imply that the arc microchannel with a bifurcation will intensify the process of particle separation since the particles completely neutrally buoyant as well as denser and lighter particles can be simultaneously separated or classified without membrane. Finally, a separation process in a series of arc channels is proposed and the process efficiencies are discussed.