Optimizing Outlet of Microcolumns for Gas Chromatography

This master thesis focused on optimizing the outlet geometry of microcolumn chips and how the chips are assembled in a miniaturized gas analysis system based on the principles of gas chromatography. The theory and literature of gas chromatography at microscales was studied and consequently several outlet designs were simulated with COMSOL Multiphysics®. Their theoretical velocity profiles were calculated at multiple positions in reference to a geometry acting as an gas sensor within the simulation models. The five most promising outlet geometry designs were in CMi at EPFL. Two process flows were used during the fabrication phase, the second including steps for creating structures of SU8 surrounding the outlets to act as nozzles. Five different outlets geometries were fabricated and four outlets were tested at various positions above a metal oxide sensor to see the influence of the fluid velocity near the sensor on the peak height and full width at half maximum of the output peaks for sample volume with one analyte. The experimental results show that there is a correlation between the velocity and measured peak height, but the full width half maximum is controlled by other aspects of the microcolumn.