Miniature gas chromatography system realized using conventional VLSI fabrication techniques applied to quantifying toxic environmental pollutants

A miniature gas chromatography (GC) system has been designed, fabricated and developed using modern silicon micromachining and VLSI circuit processing techniques. The GC system is composed of a miniature sample injector that incorporates a 10 μl sample loop; a 0.9 m long, rectangular-shaped (300 μm width and 10 μm height) capillary column coated with a 0.2 μm thick copper phthalocyanine (CuPc) stationary phase: and a dual-detector scheme based upon a CuPc-coated chemiresistor and a commercially available, 125-μm diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC system´s column, the GC system´s column itself, and the dual-detector cavity. A novel integrated circuit thin film processing technique was developed to sublime the CuPc stationary phase coating on the GC system´s column walls micromachined in the host silicon wafer substrate and the Pyrex cover plate which are subsequently electrostatically bonded together. The CuPc-coated chemiresistor was designed and fabricated using conventional VLSI circuit processing techniques. The miniature GC system has demonstrated the capability to directly and completely separate parts-per-million (ppm) ammonia and nitrogen dioxide concentrations when isothermally operated (55-80°C). With a helium carrier gas and nitrogen diluent, a 10 μl sample volume containing ammonia and nitrogen dioxide injected at 40 psi can be separated in less than 30 minutes