Generation and manipulation of magnetic droplets

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. The continuous flow generation and downstream manipulation of magnetic droplets inside a microfluidic device was investigated. Magnetic droplets were generated from aqueous ferrofluids in organic oil phase using T-junction and flow-focusing geometries in glass microfluidic devices. Due to the hydrophilic nature of glass surfaces, it was necessary to apply a hydrophobic coating in the form fluorocarbons. The size of the magnetic droplets and distance between them were controlled by adjusting the relative flow velocities of ferrofluid and oil carrier liquid. Two modes of droplet manipulation were investigated by placing small permanent magnets in the vicinity of the microfluidic channels: (i) droplet deflection across a flow chamber which could be used for sorting of droplets based on the magnetic field applied and (ii) droplet splitting at a branching junction resulting in two daughter droplets of high and low magnetite content. This study is funded by The University of Kuwait.