An enhanced-performance multisensing progressive cellular μGC: design advances and blind test results

Many environmental, industrial, and security applications demand in-field analysis of chemical vapors. Whereas microscale gas chromatographs (µGCs) are promising candidates, reliable in-field chemical analysis particularly demands repeatability, humidity tolerance, and in-field reference. Using a µGC with substantial monolithic integration (of preconcentrators, separation columns, and capacitive and photoionization detectors), this paper reports chip-level and system-level advancements towards reliable chemical analysis. Thermal management is advanced using tailored heater designs to compensate for boundary conditions and cooling. Fence electrodes are incorporated into on-chip photoionization detectors, reducing responses due to humidity by >98%. The repeatability of retention time is advanced by introducing closed-loop flow control, reducing the relative standard deviation of retention time to only 0.29-0.43%, which represents a 4-5× improvement over open-loop flow control. A miniature reservoir for a chemical reference standard is also incorporated on board, providing the ability to correct for drifts in retention time and the ability to directly measure retention times relative to the reference chemical. A set of blind false alarm tests was performed for fixed target analytes in the presence of partially coeluting interferent species. A separate set of blind chemical recognition tests was also performed for various analytes of concealed identities. Overall, the results were largely successful and showed the promise of the reported µGC instrument and modules for broad chemical screening and long-term in-field deployment.