Simultaneous Trapping of Magnetic and Diamagnetic Particles in Ferrofluid Microflows

Concentrating particles to a detectable level is often necessary and critical in many areas such as environment monitoring, food safety, and water quality control. This work demonstrates the use of magnetic force for a simultaneous trapping and concentration of magnetic and diamagnetic particles in ferrofluid microflow via a single permanent magnet. A three-dimensional numerical model is developed to simulate the flow and concentration fields of the ferrofluid under the influence of magnetic field and to track the trajectories of the two types of particles in the ferrofluid. The three different trapping processes, i.e., trapping of both types of particles, trapping of magnetic particles only, and no trapping of particles, are investigated experimentally and numerically.