COLL 9 |
| The development of miniature sensor technologies, popularly known as “electronic noses”, has been driven by the desire to detect chemical and biological agents of interest in the vapor and liquid phases. In most of the intended applications, including the detection of chemical weapons and the monitoring of air quality in closed or controlled environments, the sensors must actively detect analytes at concentrations of a few parts-per-million (ppm) or less, while simultaneously operating unobtrusively as robust, self-contained units with modest power consumption. To this end we have developed a compact and low-power, cantilever-based sensor, which we have used to detect various vapor analytes. This device is based on the static deflection of microcantilevers, which is measured via changes in piezoresistance rather than with a conventional optical beam-deflection method. The bending of the cantilevers is induced by polymeric coatings, which undergo swelling upon the reversible adsorption of analyte vapors. Unlike some mass-based chemical sensors such as surface acoustic wave (SAW) devices or quartz crystal microbalances (QCMs), our coatings consist of glassy (high modulus) rather than rubbery (low modulus) polymer coatings. Although the glassy polymer coatings increase the diffusion time of analytes into the polymer film- thus increasing the time required to identify an analyte- they are highly robust and can survive many thousands of exposures with no decrease in detection efficiency. In addition, these sensors can operate in a wide range of temperatures and can survive repeated ultra-high concentrations of analyte making them suitable for a wide variety of sensing applications. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
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Nanoscience and Nanotechnology for Chemical and Biological Defense
9:00 AM-12:00 PM, Sunday, August 19, 2007 BCEC -- 151B, Oral
Division of Colloid & Surface Chemistry |