Mass transport improvement in microscale using diluted ferrofluid and a non-uniform magnetic field

This paper demonstrates that a non-uniform magnetic field and diluted ferrofluid can improve mass transport of non-magnetic solutes in a microfluidic device. A hydrodynamic flow-focusing configuration was employed to test this hypothesis. The system consists of a core stream and two sheath streams. The core stream contains a diluted ferrofluid and a fluorescent dye. Without a magnetic field, both magnetic nanoparticles of the ferrofluid and the fluorescent dye in the core stream rely on molecular diffusion to spread transversally. The susceptibility mismatch between the core and focusing fluids results in a magnetoconvective secondary flow and subsequently the mass transport of the non-magnetic fluorescent dye. We observed a significant enhancement in mass transport of the fluorescent dye. The platform presented here could be used as a microfluidics-based gradient generator or micromixer.