Separation of complex gaseous mixtures using gas chromatography (GC) is an important step in analytical systems for environmental monitoring, medical diagnosis, and forensic science. Due to its high resolving power, analysis speed, and small sample size, GC, has become the premier technique for separation and analysis of volatile and semi-volatile organic compounds. Miniaturization of analytical systems has become a major trend which is mainly driven by advancements in microfabrication techniques and a need for portable lab-on-a-chip systems for onsite monitoring. Microfabricated columns have been explored for applications in analytical processes like GC in several research studies. These microGC columns typically have open rectangular or open circular cross sections which is a result of the etching process utilized in the fabrication. This work reports the fabrication and performance of a new generation of silicon-on-glass micro-electro-mechanical systems (MEMS) based GC columns with microposts namely "semi-packed." These columns can be fabricated on a 2 cm2-die for a 1 m-long channel or a 1 cm2-die for a 25 cm-long channel. The semi-packed columns have a higher sample capacity as the overall surface area is larger than that of open rectangular columns of the same dimensions. The separation efficiency of these columns is also superior to that of open columns due to the presence of the microposts. As compared to conventional packed columns, the semi-packed columns show lower pressure drops and a more uniform flow profile, both of which contribute to, performance in terms of separation efficiency. / Master of Science

Advances in micro-electro-mechanical-systems (MEMS) along with nanotechnology based methods have enabled the miniaturization of analytical chemistry instrumentation. The broader aim is to provide a portable, low-cost, and low-power platform for the real-time detection and identification of organic compounds in a wide variety of applications. A benchtop gas chromatography (GC) system is considered a gold standard for chemical analysis by analytical chemists. Similarly, miniaturization of key GC components (preconcentrator, separation column, detector, and pumps) using micro- and nanotechnology based techniques is an on-going research field. This dissertation specifically deals with the design, fabrication, coating, and chromatographic testing of microfabricated separation columns for GC. This work can be broadly categorized into three research areas: design and development of new column designs, introduction of new stationary phases and the development of novel fabrication methodologies for integrating functionalized thin-film into microchannels for chromatographic separations. As a part of this research, two high performance new micro column designs namely width-modulated and high-density semi-packed columns are introduced for the first time. Similarly, two new types of functionalized stationary phases are also demonstrated i.e. a highly stable and homogenous silica nanoparticles coating deposited using a layer-by-layer self-assembly scheme and a highly conformal functionalized thin aluminum oxide film deposited using atomic layer deposition. Moreover, novel thin-film patterning methods using different microfabrication technologies are also demonstrated for high-aspect ratio multicapillary and semi-packed columns. / Ph. D.