Microfluidic Devices for Manipulation and Detection of Beads and Biomolecules

Abstract: This thesis summarises work towards a Lab-on-Chip (LOC). The request for faster and more efficient chemical and biological analysis is the motivation behind the development of the LOC-concept.Microfluidic devices tend to become increasingly complex in order to include, e.g. sample delivery, manipulation, and detection, in one chip. The urge for smart and simple design of robust and low-cost microdevices is addressed and discussed.Design, fabrication and characterization of such microdevices have been demonstrated using low-cost polymer and glass microfabrication methods. The manufacturing is feasible, to a large extent, to perform outside the clean-room, and has subsequently been the chosen technique for most of the work. Issues of bonding reliability are solved by using polymer adhesive tapes.A planar electrocapture device with LOC-compatibility is demonstrated where beads are immobilised and released in a flowing stream. Retention of nanoparticles by means of electric field-flow fractionation using transparent indium tin oxide electrodes is presented. Moreover, a cast PDMS 4-way crossing is enabling a combination of liquid chromatography and capillary electrophoresis to enhance separation efficiency. Sample transport issues and a new flow-cell design in a quartz crystal microbalance bioanalyzer are also investigated. Fast bacteria counting by impedance measurements, much requested by the pharmaceutical industry for biomass monitoring, is carried out successfully.In conclusion, knowledge in micro system technology to build microdevices have been utilised to manipulate and characterise beads and cells, taking one step further towards viable Lab-on-Chip instruments.