Three-dimensional analysis and enhancement of continuous magnetic separation of particles in microfluidics

In continuous magnetic separation process, particles can be deflected and separated from the direction of laminar flow by means of magnetic force depending on their magnetic susceptibility and size as well as the flow rate. To analyze and control dynamic behavior of these particles flowing in microchannels, a three-dimensional numerical model was proposed and solved for obtaining the particle trajectories under the action of a gradient magnetic field and flow field. The magnetic force distribution and particle trajectories obtained were firstly verified by analytical and experimental results. Then, a detailed analysis for the enhancement of the continuous magnetic separation efficiency by optimizing the flow parameters and microchannel configurations was carried out. The results show that the separation efficiency can be greatly improved by controlling the flow rate ratio of the two fluid streams and introducing a broadened segment in the T-shaped microchannel. And it has been demonstrated to be effective through the sorting of 2-mu m and 5-mu m non-magnetic particles suspended in a dilute ferrofluid by a permanent magnet. The results reported could be encouraging for the design and optimization of efficient microfluidic separation systems.