This Phase I Small Business Technology Transfer project aims to develop a novel microsensor for the in-situ, real-time detection of toxic organic chemicals. The proposed microsensor will be capable of operating under field conditions, with sufficient sensitivity to permit high detection rates, and with sufficient selectivity to prevent high false alarm rates. The proposed sensor is based on a combination of gravimetric sensing and the determination of the unique photothermal spectrum of an analyte and utilizes a wavelength dispersive device and a thermal infrared detector array. This sensing technique is capable of detecting the presence of minute amounts of organic analytes with increased sensitivity and selectivity. During the detection process the sample is allowed to interact/adsorb onto the coated surface of femto-joule sensitive thermal detector. The surface of the detector will be coated with an appropriate chemical layer which preferentially adsorbs/reacts with a category of chemicals similar to the target analytes. As molecules adsorb on the thermal detector surface, various physical changes can take place such as changes in the electrical resistance when a microbolometer is used or changes in the bending due to adsorption induced stress when a microcantilever thermal detector is used. This step provides the chemical detection sensitivity comparable to recent chemical detection technologies in addition to providing the required selectivity. In order to determine the specific identity of the adsorbed molecule, a photothermal spectrum is obtained by scanning a broadband wavelength region of the detector array with the aid of a wavelength dispersive device. For the wavelengths at which the adsorbed analyte absorbs photons, the temperature of those particular detector pixels will rise proportional to the amount of analyte deposited and heat absorbed. Since different pixels will be exposed to different wavelengths, an extremely sensitive and unique photothermal signature response can be determined. The chemical detector surface can be regenerated by ohmic heating of the detector element. Miniature toxic organic sensors offer both extremely high sensitivity and are easily miniaturized, and could be readily mass produced using standard IC fabrication technology for use in high volume commercial applications, including industrial process monitoring, air and water pollution control, air quality monitoring, as well as vehicle emission monitoring.
