Separation of Cells and Cell-Sized Particles by Continuous SPLITT Fractionation Using Hydrodynamic Lift Forces

Abstract

The use of hydrodynamic lift forces for the separation of particles according to size by continuous SPLITT fractionation is explored. The mechanism for particle separation in the transport mode of SPLITT fractionation is first explained. This is followed by a discussion of the hydrodynamic lift forces that act upon particles entrained in fluid flow between the parallel bounding walls of the SPLITT cell. The effect of the bounding walls on particle motion both parallel and perpendicular to the direction of flow is explained. Computer simulations of particle trajectories are presented that predict extremely high size selectivity for the method. A parallel experimental study was carried out using both polystyrene latex particles and red blood cells. The experimental selectivity was found to be smaller than that predicted theoretically. This discrepancy is attributable to nonidealities in the construction of the SPLITT cell. Nonetheless, the results are promising. Suspensions of polystyrene particle standards (from 2 to 50 μm in diameter) demonstrate that fast and relatively clean size separations are possible provided particles differ sufficiently in size and flow conditions are properly optimized. It is also shown that the system has the potential to quickly and gently separate blood cells from plasma.