Acoustic Wave Sensors

The methods and means for ecological diagnostics make rapid strides among all the NDT and TD developing areas. To provide the atmosphere monitoring recently the good results were achieved in the development of surface-acoustics wave sensors (SAW), laser measuring systems, infrared detectors and systems based on other physical principles. 

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). 

A new chemical sensor based on surface transverse device has been developed (99) (see Sensors). It resembles a surface acoustic wave sensor with the addition of a metal grating between the tranducer and a different crystal orientation. This sensor operates at 250 mH2 and is ideally suited to measurements of surface-attached mass under fluid immersion. By immohi1i2ing atra2ine to the surface of the sensor device, the detection of atra2ine in the range of 0.06 ppb to 10 ppm was demonstrated. 

Alternatively the capillary rise can be measured using a bulk acoustic wave sensor [97Che]. (Data obtained with these methods are labelled BAW). 

Vol. 144. Surface-Launched Acoustic Wave Sensors Chemical Sensing and Thin-Film Characterization. By Michael Thompson and David Stone... 

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... 

Acoustic perturbation methods, 14 617 Acoustic streaming, 9 59, 81 Acoustic wave gravimetric technique, acoustic wave sensors and, 22 270. 

See also Gravimetric techniqugges Acoustic waves, sensors using, 22 269-270 Acoustooptic (AO) modulators, 14 676 Acousto-ultrasonics, in nondestructive evaluation, 17 425-426 Acquired Immunodeficiency Syndrome (AIDS), 3 135 25 500. See also Anti-HIV drug candidates HIV entries Nevirapine entries sulfonamide exposure in, 23 506 Acquisitions, 15 639 Acrawax C, dental wax, 8 296 9-Acridinecarbonylimidazole, as... 

Liquid-wave sensing, acoustic wave sensors and, 22 270... 

Piezoelectric biomaterials, 3 748-750 Piezoelectric ceramics, 1 708-710 U.S. market trends, l 710t Piezoelectric coefficient tensor, 11 93, 94 Piezoelectric crystals, 17 423 in acoustic wave sensors, 22 270 Piezoelectric devices, applications of, 11 103-104... 

Quartz crystal microbalances (QCMs), in acoustic wave sensors, 22 270 sensors, 23 708... 

Surface acoustic waves (SAWs), acoustic wave sensors and, 22 270 Surface-active agent(s), 12 33. See also Surfactant entries cmc values of, 24 121t general classification of, 24 144-153 nonionic, 10 665 organic esters as, 10 519 Surface-active molecules, 12 1 foaming and, 12 3... 

Acoustic wave sensors are also used to detect nerve and blister agents. The surface acoustic wave chemical agent detector (SAW Mini-CAD) is a commercially available, pocket-sized instrument that can monitor for trace levels of toxic vapors of sulfur-based mustard agents (e.g., distilled mustard) and G nerve agents (e.g., tabun, sarin, soman) with a high degree of specificity. Colorimetric tubes are the... 

The shear-mode acoustic wave sensor, when operated in liquids, measures mass accumulation in the form of a resonant frequency shift, and it measures viscous perturbations as shifts in both frequency and dissipation. The limits of device operation are purely rigid (elastic) or purely viscous interfaces. The addition of a purely rigid layer at the solid-liquid interface will result a frequency shift with no dissipation. The addition of a purely viscous layer will result in frequency and dissipation shifts, in opposite directions, where both of these shifts will be proportional to the square root of the liquid density-viscosity product v Pifti-... 

To model this, Duncan-Hewitt and Thompson [50] developed a four-layer model for a transverse-shear mode acoustic wave sensor with one face immersed in a liquid, comprised of a solid substrate (quartz/electrode) layer, an ordered surface-adjacent layer, a thin transition layer, and the bulk liquid layer. The ordered surface-adjacent layer was assumed to be more structured than the bulk, with a greater density and viscosity. For the transition layer, based on an expansion of the analysis of Tolstoi [3] and then Blake [12], the authors developed a model based on the nucleation of vacancies in the layer caused by shear stress in the liquid. The aim of this work was to explore the concept of graded surface and liquid properties, as well as their effect on observable boundary conditions. They calculated the hrst-order rate of deformation, as the product of the rate constant of densities and the concentration of vacancies in the liquid. 

Ann. Occup. Hyg. Ballantine DS. Acoustic wave sensors theory, design, and physico-chemical applications. San Diego, CA Academic Press, 1997. 

Tan YG, Peng H, Liang CD, Yao SZ. A new assay system for phenacetin using biomimic bulk acoustic wave sensor with a molecularly imprinted polymer coating. Sens AcUiat B 2001 73 179-184. 

Thompson M, Stone DC (1997) Surface-launched acoustic wave sensors chemical sensing and thin-film characterization. Wiley, New York... 

Potyrailo and May used the acoustic-wave sensor to quantify cresol and benzo-quinone [21]. They tested sensors for the quantification of cresol and benzoqui-none in mixtures with multivariate regression analysis tools. Only 2 mL of solution was used for analysis, which included cresol and/or benzoquinone on the order of pg. After the sensor had been calibrated with a standard library of pure cresol or benzoquinone solution, 19 model libraries, including mixtures of cresol and benzoquinone, were analyzed (Fig. 8.9). A linear correlation occurs between actual... 

Martin, S.P., D.J. Lamb, J.M. Lynch, et al. 2004. Enzyme-based determination of cholesterol using the quartz crystal acoustic wave sensor. Anal. Chim. Acta 487 91-100. 

Li, P.C.H., Wang, W.J., Parameswaran, M., An acoustic wave sensor incorporated with a microfluidic chip for analyzing muscle cell contraction. Analyst 2003, 128, 225-231. 

Kim, E.S., Zhu, X., Microfluidic motion generation with acoustic waves. Sensors Actuators A 1998, 66, 355-360. 

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