Microfluidic based magnetic separator for biological applications

Abstract

Macro scale magnetic separation of pure biological particles from a complex biological sample is a key technique performed in clinical and research settings. This thesis focuses on the development of a microfluidic based magnetic separator for biological applications. The work presented covers design, simulation, fabrication and testing of the magnetic separator. The magnetic separator design consists of a micron-sized channel fabricated in a biocompatible polymer, containing one inlet and three outlets. Close to the channel wall are soft permalloy elements. The external magnetic flux is provided by the permanent magnets situated on either side of the channel. Theoretical aspects of the design are discussed and special attention is paid to investigating the effects of the magnetic and fluidic forces acting within the microdevice. Fabrication of the magnetic separator was carried out in the Microsystems Engineering Centre, Heriot Watt University and at Epigem Ltd., Redcar, U.K. The manufacturing processes investigated include methods for rapid prototyping and UV-photolithography. CO2 laser ablation and powder blasting of PMMA were investigated as rapid prototyping techniques. Using UV-photolithography magnetic separators were realised in PDMS and in SU-8. Soft permalloy elements were fabricated using UV-LIGA and the correct permalloy ratio (Ni80Fe20) evaluated. Ultimately three magnetic separation systems have been successfully fabricated based on the different fabrication approaches. Magnetic separation on chip was successfully demonstrated for all three devices fabricated. Flow cytometry a highly accurate method of particle counting and analysis was used to verify the separation efficiency. Experimental testing results have shown that magnetic and non-magnetic beads can be separated with high efficiency.