Design of a Chemical Agent Detector Based on Polymer Coated Surface Acoustic Wave (SAW) Resonator Technology

This dissertation presents the design of a unique prototype chemical agent detector which utilizes an array of polymer coated SAW resonators as the sensor elements. The design\u27s particular embodiment is that of a testing platform for evaluating the utility of constructing a portable chemical agent detector, utilizing commercially available SAW resonators. It involves the consolidation of the sub-systems comprising a large laboratory development system, into a portable enclosure. A combination of design techniques, utilized to achieve an overall balance between the physical dimensions of the system and its detection performance, comprises the unique nature of the overall design of this detection system. Such techniques include; sensor power cycling, individually phase-tunable sensor oscillators, single step down conversion and the locality of the sensor\u27s driving circuitry and sensing chamber. A frequency shift model is developed to characterize the device\u27s response to target analytes. Reported here are the results of the preliminary tests of the detector system and the verifications of the device\u27s operation as per the design requirements. Further, an assay of the system noise is undertaken, and the detector\u27s limit of detection (LOD) is reported. The analytes used in this investigation were simulants of nerve and mustard gas as well as the interferent compound diesel. Among others, the following conclusions are reported: 1) that a mass loading model can adequately describe the frequency shifts of the SAW resonators utilized for sorption sensing; 2) that the quality factor of a polymer coated SAW resonator ultimately determines the noise performance of the driving oscillator; 3) that the lowest usable quality factor for the designed oscillator is 2500; 4) that the implementation of individual phase-tuning networks for each sensor in the sensor array can adequately compensate for phase variations among these sensors, and 5) that commercially available SAW resonators coated with chemo-selective polymers provide a reasonably inexpensive and reliable solution to the detection of chemical warfare agents when incorporated into a miniaturized sensing platform