On-chip free-flow magnetophoresis: Separation and detection of mixtures of magnetic particles in continuous flow

The complete separation of mixtures of magnetic particles was achieved by on-chip free-flow magnetophoresis. In continuous flow, magnetic particles were deflected from the direction of larninar flow by a perpendicular magnetic field depending on their magnetic susceptibility and size and on the flow rate. 2.8 and 4.5 mu m superparamagnetic particles with magnetic susceptibilities of 1.1 X 10(-4) and 1.6 x 10(-4) m(3) kg(-1), respectively, could be completely separated from each other reproducibly. The separated particles were detected by video observation and also by on-chip laser light scattering. Potential applications of this separation method include sorting of magnetic micro- and nanoparticles as well as magnetically labelled cells. (c) 2006 Elsevier B.V. All rights reserved.