The Development of a Low-Cost Microfluidic Magnetic Separation System

Microfluidic systems show excellent promise for analytical applications, due to their ability to rapidly process minute sample quantities with high sensitivity. At the same time, functionalised superparamagnetic magnetic microbeads and nanoparticles have emerged as useful substrates for biomedical applications such as bioassays, fuelling research into tools for the manipulation of magnetic particles in microfluidic channels. This thesis describes the design, fabrication and evaluation of microfluidic systems for the separation of magnetic microbeads and nanoparticles. Microfluidic devices were produced in polydimethylsiloxane using a low-cost rapid prototyping process. Channels 300μm or greater in width were accurately reproduced using this method. Laminar flow was observed in the channels of these devices, allowing two-phase flow to be used for separation purposes. Magnetic field gradients of 25-500 T/m were generated in the microchannels using either permanent magnets or soft magnetic materials. The performance of a permanent magnet-based separation system was evaluated, and it was found that the system could extract magnetic microbeads with an efficiency of up to 75%. A limited ability to separate magnetic microbeads on the basis of magnetic moment and/or particle size was also demonstrated.