An array of 32 sensor elements with single-walled carbon nanotubes (SWCNTs) as the sensing medium has been fabricated. The microfabrication approach used allows reduction of the chip size and increases the number of sensor elements in a chip and is amenable for large wafer scale-up. The sensor array chip is designed as an electronic nose for use with the aid of a pattern recognition algorithm. The sensor chips were tested for NO 2 sensing and interfering effects from humidity and a background of chlorine. The results indicate that NO 2 can be detected at low concentration levels of 0.5 ppm in the presence of chlorine at 30 times higher concentrations. The sensor response is affected by humidity, which implies that the training data set for NO 2 detection needs to be generated for multiple humidity levels for interpolation purposes during field use.
Pressed PZT Piezoelectric disks were embedded in a range of materials and their properties monitored under a wide range of conditions. The output depends on the temperature and pressure exerted on the PZT by the surrounding material and by the mechanical impedance mismatch between the embedded PZT and the surroundings. By monitoring the "Q" of the PZT (the ratio of energy stored to energy dissipated) it was found that the PZT discs could be used as cure monitors, strain gauges, and as embedded dynamic mechanical property estimators. This latter property is a means of gauging the "health of the material", and its degradation with time. These sensors were part of the MTSIUS Navy embedded sensor program, so the sensors could be addressed and read remotely. The techniques, the data and the applications are discussed in this paper.
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