Micro-Fabricated Packed Metal Gas Preconcentrator for Low Detection Limit Exhaled VOC Gas Measurements

Gas preconcentrator is critical for many microanalyzer and allows the monitoring of ultra-low concentrations of VOC gas in the sub-ppm level. Especially, it can be used in field test to analyze the low-concentration exhaled VOC gases by improving the gas detection limit for the purpose of noninvasive medical diagnoses. In this paper, a micro metal gas preconcentrator (MGP) was fabricated by using laser etching technology (LET), which is a very powerful means to process more sophisticated and high-quality trenches compared with traditional machining. The preconcentrator chip consists of an array of microchannels that are filled with activeated-carbon-based sorbent (Carboxen-1000) as the extraction medium. The main structure of chip is made of copper (C11000) because of its good thermal conductivity and small specific heat capacity. Compared with Si substrate, C11000 has better thermal properties, which is advantageous for achieving high concentration factor at relative low power. The copper channel layer is covered with the upper plate of the same material using of vacuum diffusion welding (VDW). At the bottom of the chip the platinum heater is deposited to quickly elevate temperature during its activation and desorption processes. The MGP has flat dimensions of 16 mm x 12.6 mm and a total inner volume about 14.4 mu L with no filling the adsorbent granules. The MGP can be connected with GC (Gas chromatography) column and photo ionization detector (PID) to realize ultra-low concentration gas detection.