Magnetofluidic spreading: the roles of magnetoviscous effect, bulk magnetic force, magnetophoresis and convective transport

The proposed project aims at the fundamental investigation of magnetofluidic spreading in microchannels. The use of magnetism provides a wireless and heat-free actuation concept for microfluidics. Micro magnetofluidics, the combination of magnetism and microfluidics, offers fundamentally new capabilities for the manipulation of heat-sensitive and pH-sensitive bioparticles such as bacteria, viruses and cells. In a preliminary study, we discovered the spreading phenomenon of the magnetic fluid core in a three-stream flow system under a uniform magnetic field. We called this phenomenon magnetofluidic spreading. We hypothesise that the four factors contributing to this phenomenon are: (i) the magnetoviscous effect, or the increase in viscosity of the magnetic fluid under an applied magnetic field, (ii) the magnetic force due to a gradient in magnetic properties, (iii) magnetophoresis and (iv) convective transport.--We will use a solution of dispersed magnetic particles as the magnetic fluid. We will experimentally investigate the role of magnetoviscous effect by varying the field strength, the size and the concentration of magnetic particles, as well as varying the relative orientation of the flow. We will investigate the role of magnetic force caused by the magnetic susceptibility gradient using ferrofluids, which show a negligible magnetoviscous effect. Magnetic force may induce secondary flow and instability that will be tested and confirmed experimentally. We will investigate how magnetic force acting on individual magnetic particles causes magnetophoresis. We will vary the flow rate to test the impact of convective transport on magnetofluidic spreading. We will formulate numerical models to gain more insights into the physics of this phenomenon. The results of this project will provide novel wireless technologies for important microfluidic applications such as micromixers, cytometers, cell sorters and tuneable optofludics. We intend to introduce these technologies into products and processes of the microfluidics foundry at SIMTech, A*STAR.