Transport of Magnetic Particles Under a Uniform Magnetic Field in Microchannels

This paper reports the numerical and experimental investigation on magnetic particle concentration in a uniform magnetic field. The flow system consists of water-based ferrofluid and glycerol/DI water mixture streams. Two regimes were observed with spreading and mixing phenomena. With a low magnetic field strength, the spread of magnetic particles is caused by improved diffusion migration. With a relatively high field strength, instability at the interface would occur due to the mismatch in magnetization of the fluid streams. The transport of magnetic particles is induced by chaotic mixing of the fluids caused by a secondary flow. The mixing phenomena are characterized by magnetic flux density. For configuration with flow rate and viscosity ratio (between diamagnetic and magnetic streams) being set at 1 and 0.5, the mixing efficiency analyzed based on magnetic particles concentration increases approximately by 0.3 at around 3.5 mT. This value of magnetic flux density indicates the requirement on instability inception. The mixing efficiency increases with magnetic flux density increases further. Complete mixing can be achieved with a magnetic flux density at around 10 mT. The magnetic approach offers a wireless, heat-free and pH-independent solution for a lab-on-a-chip system.