Fast Mixing of the Ferrofluid in Microchannels

The mixing of the ferrofluid in microfluidic chips was investigated in this study. Mixing processes of the ferrofluid in the presence of a permanent magnet are highly different from that of pure diffusion. The magnetic field re-distributes the ferrofluid and the mixing efficiencies vary with the positions of the magnet and the volumetric flow rates of the fluids. With the suitable setup of the magnet, the mixing efficiencies can reach more than 90% within one characterisitic width of the channel. By the suitable design of the microfluidic chips and the proper position of the magnet, the efficient mixing of the ferrofluid in PDMS microfluidic chips can be performed.