(224i) Vector Separation of Particles Using an Array of Slanted Ramps

The separation of the different components of complex suspensions with high selectivity is a crucial step in many applications. Bernate and Drazer (PRL 2012) showed that an array of slanted grooves and a uniform force field can be used to induce vector separation, in which different species migrate in different directions in a planar microfluidic device. In the deterministic limit, the extent of deflection of a given particle depends on: i) the magnitude of the hydrodynamic drag advecting the particle relative to retarding force due to the external field that the particle experiences in the ramps leading out of the grooves, and ii) the width of the ramps. The stronger the response of a given particle to the external field, the more it will get deflected surmounting the ramp. Here, we present experiments in a microfluidic platform exploiting the same mechanism and show the versatility and high selectivity of the device. First, we separate beads based on their size and density simply using gravity. We then separate magnetic particles from non-magnetic ones in the presence of a magnetic field, and show that  subpopulations of cells magnetically labeled can be similarly depleted resulting in the enrichment of unlabeled cells.