Surface acoustic wave sensor technique

C. G. Fox, J. F. Alder Surface Acoustic Wave Sensors for Atmospheric Gas Monitoring." in P. T. Moseley. J. Norris, D. E. Williams (eds.) Techniques and Mechanism in Gas Sensing, Adam Hilgcr, Bristol 1991. chap. 13. 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

Macrocyclic Compounds in Analytical Chemistry. Edited by Yury A. Zolotov Surface-Launched Acoustic Wave Sensors Chemical Sensing and Thin-Film Characterization. By Michael Thompson and David Stone Modern Isotope Ratio Mass Spectrometry. Edited by T. J. Platzner High Performance Capillary Electrophoresis Theory, Techniques, and Applications. Edited by Morteza G. Khaledi... 

The analysis of thin supported films by N2 adsorption is often difficult due to the very small percentage of pore volume contributed by the thin layer relative to that of the support. Usually it is necessary to scrape off most of the bulk support layer to increase the pore volume percentage of the thin film. Recent technical improvements in pressure sensors on commercial apparatus (reaching now a sensitivity of 5.10 mmHg) or new sophisticated detection techniques using surface acoustic waves may in some cases solve this problem. 

The combination of chemical and biological sensors with flow injection has been demonstrated. Both more-traditional-type sensors such as pH electrodes and newer sensors such as fiber optics and surface acoustic wave detectors have been incorporated into FIA systems with success. An advantage that FIA brings to the sensor field is the possibility of turning a moderately selective sensor into a selective sensor by incorporating into the FIA system some type of selectivity enhancement technique such as gas diffusion, dialysis, and reactors. Finally the FIA systems permit renewable systems since sensor surfaces and reaction cells can be washed, surface regenerated, and reagents replenished on demand. 

These researches have demonstrated the possibility of combining acoustic wave technique and electrospinning technique to develop acoustic wave sensor for contamination detection. Through regulating the structure of the nanofibrous membranes and modifying with different probes, the sensors could obtain higher surface activity and analyte sensitivity and stability. 

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