Increasing the Sensitivity of Surface Acoustic Wave (SAW) Chemical Sensors and other Chemical Sensing Investigations

摘要

The work involves the fabrication and testing of three different surface acoustic wave (SAW) device designs, an investigation of nanowires sensitive to chemicals and preconcentrator prototypes to include with chemical sensors. The SAW chemical sensor designs include modifications to a basic SAW device to see if the sensitivity of the SAW device is increased. The modifications consist of etched trenches along the propagation field, coating the device with carbon nanotubes (CNTs) under the chemically sensitive layer and coating CNTs on top of the chemically sensitive layer. SAW devices are coated with Nafion(trademark), a polymer sensitive to ethanol. The tests indicate that trenches etched between the transducer fields increase the sensitivity of the SAW devices. The increase of sensitivity is signified by a shift of peak frequency of an extra 100kHz over the unaltered device after five minutes of flowing ethanol. Testing of the nanowires involves measuring the resistance of palladium, polypyrrole and polyaniline nanowires. Investigation of the nanowires indicates that they are less suited to detecting chemicals in a non-ideal measurement circumstance than SAW devices. Preconcentrators are another way to improve the sensitivity of chemical sensors. Some preconcentrator prototypes fabricated in the PolyMUMPs(trademark) system are tested and evaluated for heating characteristics and abilities.. A grid pattern presents the best way to heat a large surface area the most uniformly. Coating the devices with CNTs also increases the heat to which devices can be heated and decreases the amount of time that it takes to heat the devices.