Publications

Networked systems of low-cost, small, integrable chemical sensors will enable monitoring of Nonproliferation and Materials Control targets and chemical weapons threats. Sandia-designed prototype chemical sensor systems are undergoing extended field testing supported by DOE and other government agencies. A required surety component will be verification of microanalytical system performance, which can be achieved by providing a programmable source of chemical signature(s) for autonomous calibration of analytical systems. In addition, such a controlled chemical source could be used to dispense microaliquots of derivatization reagents, extending the analysis capability of chemical sensors to a wider range of targets. We have developed a microfabricated system for controlled release of selected compounds (calibrants) into the analytical stream of microsensor systems. To minimize pumping and valve requirements of microfluidic systems, and to avoid degradation issues associated with storage of dilute solutions, we have utilized thermally labile organic salts as solid-phase reservoir materials. Reproducible deposition of tetrapropyl ammonium hydroxide onto arrays of microfabricated heating elements can provide a pair of calibration marker compounds (one fast and one slow-eluting compound) for GC analyses. The use of this microaliquot gas source array for hydrogen generation is currently under further development. The goal of the latter effort will be to provide a source of high-pressure, low viscosity GC carrier gas for Sandia's next-generation microfabricated gas-phase chemical analysis systems.

Sandia National Labs has developed an autonomous, hand-held system for sensitive/selective detection of gas-phase chemicals. Through the sequential connection of microfabricated preconcentrators (PC), gas chromatography columns (GC) and a surface acoustic wave (SAW) detector arrays, the MicroChemLab{trademark} system is capable of selective and sensitive chemical detection in real-world environments. To date, interconnection of these key components has primarily been achieved in a hybrid fashion on a circuit board modified to include fluidic connections. The monolithic integration of the PC and GC with a silicon-based acoustic detector is the subject of this work.