Inertia-magnetic particle sorting in microfluidic devices: a numerical parametric investigation

Microfluidic-based sorting systems are an integral part of many biological applications, where sorting of cells, microorganisms, and particles is of interest. In this paper, a computational fluid dynamics model is established to expand investigations on a hybrid microparticle sorting method, which combines inertia-magnetic focusing and hydrodynamic separation, known as multiplex inertia-magnetic fractionation (MIMF). This microfluidic device consists of two regions, i.e. a narrow microchannel with a magnet on its side for inertial and magnetophoretic focusing of particles and a downstream wide hydrodynamic expansion zone for particles' separation and imaging. A Lagrangian-Eulerian framework was adopted to simulate particle trajectories using the ANSYS-Fluent discrete phase modeling (DPM) approach. Acting forces that were considered to predict particle trajectories included the drag, inertial lift, Saffman lift, gravitational, and magnetophoretic forces. User-defined functions were used for inertial lift and magnetophoretic forces that are not built-in relations in the ANSYS-Fluent DPM. Numerical results were verified and validated against the experimental data for MIMF of 5 and 11 mu m magnetic particles at flow rates of 0.5-5 mL/h. Particles fractionation throughput and purity in the expansion region could be predicted with errors of 6% and 2%, respectfully. The validated model was then used to perform a numerical parametric study on the unknown effects of magnetization, particle size, higher flow rates, and fluid viscosity on MIMF. The presented numerical approach can be used as a tool for future experimental design of inertia-magnetophoretic microfluidic particle sorting devices.