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A major research effort has been devoted over the years for the development of chemical sensors for the detection of chemical and explosive vapors. However, the deployment of such chemical sensors will require the use of multiple sensors probably tens of sensors in a sensor package to achieve selective detection. In order to keep the overall detector unit small, miniature sensors with sufficient sensitivity of detection will be needed.We report sensitive detection of dimethyl methylphosphonate DMMP, a stimulant for the nerve agents, using a miniature sensor unit based on piezoresistive microcantilevers. The sensor can detect parts-per-trillion concentrations of DMMP within 10 s exposure times. The small size of the sensor makes it ideally suited for electronic nose applications. © 2007 American Institute of Physics.

MEMS-based microcantilevers have been proposed for a variety of biological and chemical sensing applications. Measuring the magnitude of microcantilever deflection due to adsorption-induced bending, and following the variation in the resonant frequency of the microcantilevers due to the adsorbed mass are two techniques commonly employed for sensing analytes. Apart from possessing a high level of sensitivity to small changes in mass, microcantilevers are also very sensitive to small changes in temperature and hence the flow of heat. One way of achieving high sensitivity in thermal measurements is by using a bimaterial microcantilever and measuring its deflection as a result of thermal fluctuations. Commercially available piezoresistive microcantilevers are an example of bimaterial cantilevers and in this study, we propose the use of such cantilevers for sensing explosives. We show that sensing can be accomplished by following the differences in the thermal response of the cantilevers introduced by the presence of explosives adsorbed from the vapor phase onto the surface of the cantilever. We discuss the issues involved in determining the sensitivity of detection and selectivity of detection., This article is from the Mat. Res. Soc. Symp. Proc. Vol. 723, (pages), 2002. Prepared in cooperation with the Univ. of California at Irvine; Portland State Univ., Oregon; Texas A and M Univ., College Station, Texas; Univ. of California at San Diego, La Jolla, California, p173-178. This article is from ADA412559 Materials Research Society Symposium Proceedings. Volume 723. Molecularly Imprinted Materials - Sensors and Other Devices. Symposia Held in San Francisco, California on April 2-5, 2002

Measurements are reported on the rate constants and cross sections of electron attachment to SF6, c-C4F6, and C6F6 as a function of temperature in the range 300 to 600 K. Measurements are reported, also, of the rate constant for the temperature enhanced autodetachment from SF6(-), c-C4F6(-) and C6F6(-) in the same temperature range. New techniques are described for the accurate measurement of the effect of temperature on electron attachment and detachment processes and on the photodetachment of anions in dense fluids. Photodetachment measurements on SF6(-) and C6F6(-) are reported and discussed. Optically enhanced electron attachment has been observed in laser irradiated H2, SiH4 and CH4. The usefulness of these findings in understanding gas dielecrtic phenomena and plasma processes in gas-discharge-based technologies is discussed.