Magnetic particles are widely used in chemical, biological, and medical applications, and their efficient separation based on size and magnetic properties is particularly important when dealing with realistic particle populations exhibiting continuous and broad size distributions. In this study, a continuous and high-throughput millifluidic magnetic separation chip is presented together with a numerical simulation framework for outlet-resolved magnetic fractionation that explicitly accounts for continuous particle size distributions. Implemented in COMSOL Multiphysics by coupling CFD, AC/DC, and particle tracing modules, the framework systematically analyses how chip geometry, flow conditions, dynamic viscosity (temperature), and magnetic configurations – particularly variations in magnet number and arrangement – govern the separation of particles with continuous size distributions and different magnetic permeabilities. Colour maps and outlet-resolved size interval plots are employed to visualise the particle size ranges captured at each outlet, enabling particle size distribution characterisation in addition to magnetic separation. The results demonstrate effective fractionation of particles over a 0–4 µm size range using a single magnet and finer separation within the 0–1 µm range using magnet arrays. In summary, beyond demonstrating the performance of a millifluidic magnetic separation chip, this work provides a generalisable, distribution-level numerical simulation framework that supports the design optimisation and experimental implementation of high-efficiency magnetic separation.
Xu et al. (Mon,) studied this question.