Microstructures for Chemical Analysis : Design, Fabrication and Characterisation

Abstract: The interest for miniaturisation in chemical and biological analysis has increased in recent years. In this work, the design, fabrication and characterisation of tools for microanalysis have been studied. The focus is set on polymer microchips for applications in chemical analysis. The work consists of three parts: design and fabrication of paraffin microactuators, design and fabrication of polymer microchips as interfaces in electrospray ionisation mass spectrometry (ESI-MS), and characterisation of conducting films for fused silica capillaries as interfaces in ESI-MS.The principle of the paraffin actuators is based on the volume increase resulting from paraffin melting. Paraffin expansion is utilised to cause membrane deflection. The first plastic microactuator using paraffin as the actuator material was successfully demonstrated.The microchips as interfaces in ESI-MS have been designed with the objective that the interface should be as much a part of the microchip as possible, and as to as large extent as possible, be fabricated in the same step as the microchannels. Sheathless electrospray from microchips was demonstrated for the first time. In addition a simplified fabrication process for ESI-MS interfaces in poly(dimethyl siloxane) (PDMS) was developed.The degradation of conductive coatings for sheathless ESI-MS on fused silica capillaries was studied. It was shown that electrochemical experiments could successfully be used to simulate the electrospray conditions and predict the failure of different gold coatings.It was concluded that a common issue in the fabrication of thermoplastic microchips is the crucial sealing of microchannels and cavities. From this point of view, PDMS is a more advantageous material in microfluidics.