Abstract
Gas chromatography (GC) is used for organic and inorganic gas detection with a range of applications including screening for chemical warfare agents (CWA), breath analysis for diagnostics or law enforcement purposes, and air pollutants/indoor air quality monitoring of homes and commercial buildings. A field-portable, light weight, low power, rapid response, micro-gas chromatography (μGC) system is essential for such applications. We describe the design, fabrication and packaging of μGC on monolithically-integrated Si dies, comprised of a preconcentrator (PC), μGC column, detector and coatings for each of these components. An important feature of our system is that the same mechanical micro resonator design is used for the PC and detector. We demonstrate system performance by detecting four different CWA simulants within 2 min. We present theoretical analyses for cost/power comparisons of monolithic versus hybrid μGC systems. We discuss thermal isolation in monolithic systems to improve overall performance. Our monolithically-integrated μGC, relative to its hybrid cousin, will afford equal or slightly lower cost, a footprint that is 1/2 to 1/3 the size and an improved resolution of 4 to 25%.
Highlights
Gas chromatography (GC) is a widely employed technique with a variety of civilian and defense related applications
The GC column is coated with a stationary phase, described shortly, in a fixture that allows a temporary fluidic connection to be made to the device [Figure 3(c,d)]
In order to understand the performance of the PC and μGC, their output was connected to a standard, commercial flame ionization detector (FID)
Summary
Gas chromatography (GC) is a widely employed technique with a variety of civilian and defense related applications. We and others have been developing GC systems possessing the attributes of rapid response, small footprint, low cost, low power, light weight, battery-operated units [3,6,7,8,9,10,11,12] These μGC systems possess higher resolution with narrow, small columns that have low dead volume and improved sensitivity with smaller sample volumes. The entire μGC system was assembled from separately fabricated subsystems [9] or the PC alone [10] or the PC and the column were fabricated together [11] or the column alone was micromachined [12], with some GCs weighing 10 kg [13] To overcome these limitations we describe the design, fabrication and monolithic integration of the PC, GC column and detector using Si dies. We present a cost analysis model, discuss opportunities and challenges confronting monolithic integration and comment on ideas to overcome thermal isolation arising from monolithic integration
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