This paper reports a unique GC-on-chip module comprising a monolithically integrated semi-packed micro separation column (μSC) and a highly sensitive micro helium discharge photoionization detector (μDPID). While semi-packed μSC with atomic layer deposited (ALD) alumina as a stationary phase provides high separation performance, the μDPID implemented for the first time in a silicon-glass architecture inherits the desirable features of being universal, non-destructive, low power consumption (1.4 mW), and responsive. The integrated chip is 1.5 cm × 3 cm in size and requires a two-mask fabrication process. Monolithic integration alleviates the need for transfer lines between the column and the detector which improves the performance of the individual components with overall reduced fabrication and implementation costs. The chip is capable of operating under the isothermal as well as temperature and flow programming conditions to achieve rapid chromatographic analysis. The chip performance was investigated with two samples: 1) a multi-analyte gas mixture consisting of eight compounds ranging from 98 °C to 174 °C in boiling point and 2) a mixture containing higher alkanes (C9-C12). Our experiments indicate that the chip is capable of providing rapid chromatographic separation and detection of these compounds (<1 min) through the optimization of flow and temperature programming conditions. The GC-on-chip demonstrated a minimum detection limit of ~10 pg which is on a par with the widely used destructive flame ionization detector (FID).

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A controllable and high-yield surface functionalization of silicon microchannels using layer-by-layer (LbL) self-assembly of SiO 2 nanoparticles (SNPs) is presented. The application of SNPs (45 nm average diameter) coating as a stationary phase for chromatographic separation is also demonstrated with surface functionalization using chloroalkylsilanes. This method facilitates a simple, low-cost, and parallel processing scheme that also provides homogeneous and stable nanoparticle-based stationary phases with ease of control over the coating thickness. The SNP-functionalized microfabricated columns with either single capillary channels (1 m long, 150 μm wide, 240 μm deep) or very narrow multicapillary channels (25 cm long, 30 μm wide, 240 μm deep, 16 parallel channels) successfully separated a multicomponent gas mixture with a wide range of boiling points with high reproducibility. B ecause of recent advancements and the emergence of microelectromechanical systems (MEMS), energy-efficient integrated microgas chromatography (μGC) systems have attracted considerable attention. This system, upon complete realization, could expand the range of applications for real-time and rapid on-site analysis at a lower cost.1−10 As a key component in μGC systems, conventional meters-long separation columns are necessarily replaced with microfabricated silicon columns on the order of a few square centimeters. The separation ability and efficiency of the columns are directly related to the quality of the stationary phase. Using conventional coating techniques on microfabricated columns (e.g., dynamic or static coatings of functionalized polysiloxane polymers), especially for highaspect-ratio (HAR) rectangular-shaped capillary channels, present major challenges toward obtaining stable, reproducible, and uniform coatings. 11There have been progressive research efforts toward the development of coating techniques that yield chemically inert, thermally stable, selective, and robust stationary phases. Specifically, nanotechnology-based phases have opened up countless prospects for applications in conventional as well as microfabricated separation columns with nanoscale controllability, simplicity, and flexibility.12,13 Recently, carbon nanotubes 14,15 and thiol-encapsulated gold nanoparticles 16 have been utilized for gas chromatography (GC) separations. Our group has reported on the capability of thiol monolayers on electrodeposited gold surfaces as a stationary phase for microfabricated columns by combining nanofabrication and microfabrication techniques. 17,18The excellent adsorption properties of silica for organics has long been demonstrated as a stationary phase medium for conventional columns (silica gel, Celite) 19 and, more recently, by employing the MEMS-compatible sputtering technique for microfabricated columns.20 SiO 2 nanoparticles (SNPs), because of their small and uniform size, high surface area, chemical inertness, and thermal stability, are excellent candidates for stationary phases. SNPs have also been dispe...