Magnetic Focusing and Hydrodynamic Deflection of Micro-Particles in A Microdevice

Abstract

Cell and particle sorting is indispensable to drive medical diagnosis and immunomagnetic separation for applications in health and water monitoring. Microfluidic sorting methods offer cost-effective solutions to handling particles against conventional methods such as filtration and chromatography. But their sorting performances suffer from issues such as requirement of adulterating sheath flow in Pinched Flow Fractionation (PFF) [1]; low throughput in hydrodynamic filtration [2] and deterministic lateral displacement [3]; complex fabrication in magnetophoresis [4] and external energy consumption in dielectrophoresis [5] and acoustic separation [6]. We report a two-stage sorting microdevice capable of magnetophoretic focusing of 5µm and 11µm superparamagnetic particles and their hydrodynamic sorting at high throughput with no sheath flow. The device deploys magnetophoresis to align the randomly distributed superparamagnetic particles along the wall of a 40µm-wide microchannel using a permanent magnet. Center of particles follow distinct streamlines lying at a distance equal to their respective radii from the wall. The aligned particles then enter into an 8mm-wide expansion region hence getting separated from each other due to the increase in intra-distance between their respective laminar streamlines. We have achieved a throughput of 6ml/h, separation purity of 90%, and particles processing capacity of 10E6 per hour which is comparable or better than the above-mentioned methods with yet the advantage of sheath-flow less sorting of particles. These research findings shall be applied to innovate a microchip for separation of microorganism from water samples for its quality monitoring.[1] Yamada, M., Anal. Chem. 76, 5465 (2004).[2] Yamada, M. Lab Chip 5, 1233 (2005).[3] Huang, L. R., Science 304, 987 (2004).[4] Adams, J. D., PNAS 105, 18165 (2008).[5] Wang, X. Cell Separation by Dielectrophoretic. 72, 832 (2000).[6] Petersson, F. Lab Chip 5, 20 (2005).