Surface acoustic wave gas sensors

Nieuwenhuizen, M.S. and Harteveld, J.L.N., Development of a surface acoustic wave gas sensor for organophosphorus nerve agents employing lanthanide compounds as the chemical interface, Ta/anta, 41, 461 (1994). 

Figure 2. Surface acoustic wave gas sensor consisting of dual delay line oscillator[4].

Sadek A. Z., Wlodarski W., Shin K., Kaner R. B., and Kalantar-zadeh K., A layered surface acoustic wave gas sensor based on a polyaniline/In203 nanofibre composite. Nanotechnology, 17, 4488-4492, 2006. 

Kondoh J., Shiokawa S., Rapp M., and Stier S., Simulation of viscoelastic effects of polymer coatings on surface acoustic wave gas sensor under consideration of film thickness, Jpn J. Appl. Phys., 37, 2842-2848, 1998. 

Ricco A. J., Martin S. J., and Zipperian T. E., Surface acoustic wave gas sensors based on film conductivity changes. Sens. Actuators, 8, 1985. 

A.Z. Sadek, C.O. Baker, D.A. Powell, W. Wlodarski, R.B. Kaner, and K. Kalantar-Zadeh, Polyaniline nanofiber based surface acoustic wave gas sensors - effect of nanofiber diameter on H2 response, IEEE Sens. J., 7, 213-218 (2007). 

Sadek, A. Z. Baker, C. O. Powell, D. A. Wlodarski, W Kaner, R. B. Kalantar-zadeh, K. Polyandine nanofiber based surface acoustic wave gas sensors—effect of nanofiber diameter on H2 response. Inst. Eelectrical Electronics Engineers Inc. 2007, 2,213-218. 

Mortet V, Williams OA, Haenen K (2008) Diamond a material for acoustic devices. Phys Stat Sol 205(5) 1009-1020 Nieuwenhuizen MS, Nederlof AJ (1988) Surface acoustic wave gas sensor for nitrogen dioxide using phthalocyanines as chemical interfaces. Effects of nitric oxide, halogen gases, and prolonged heat treatment. Anal Chem 60 236-240... 

Ricco AJ, Martin SJ (1992) Thin metal film characterization and chemical sensors monitoring electronic conductivity, mass loading and mechanical properties with surface acoustic wave devices. Thin Solid Films 206 94-101 Ricco AJ, Martin SJ, Zipperian TE (1985) Surface acoustic wave gas sensor based on film conductivity changes. Sens Actuators 8 319-333... 

Ahmadi, S., Hassani, F., Ugli, O., Ahmadi, S., Kortnan, C. and Zaghloul, M. (2003) Integrated CMOS surface acoustic wave gas sensor design and characteristics. Proceedings of IEEE Sensors, 2, 1199. 

Surface and Interfacial Properties of Surface Acoustic Wave Gas Sensors... 

Surface acoustic wave (SAW) sensor as noses for gas detection and identification... 

Abstract A brief overview is given for a variety of sensors for the detection of chemical warfare agents (CWA) semiconductor thick- or thin-fihn gas sensors with oxide and noble metal additives, surface acoustic wave (SAW) sensors with a polymer membrane, and an ion mobility sensor (IMS). This is followed by discussion on the preparation methods for the sensing materials employed in semiconducting devices, and SAW sensors are introduced.The chapter closes with the results and observations from the examination and study of these devices. 

A coated surface-acoustic-wave (SAW) sensor capable of real-time, selective measurement of vinyl acetate vapor in the presence of several olefin and non-olefin cocontaminants is described. The coating film en loyed consists of the solid platinum-ethylene Ji-complex, trans-PtCl (ethylene)(pyridine). occluded in a polyisobutylene matrix. Exposure to vinyl acetate results in displacement of ethylene from the cott lex and formation of the vinyl acetate-substituted complex. Subsequent regeneration of the original reagent is possible by treatment with ethylene gas, in situ. A lower detection limit of 5 ppm of vinyl acetate is achieved for operation at 46 C. The industrial-hygiene applications of the sensor are discussed. 

J.W Grate, A. Snow, D.S. BaUantine, H. Wohltjen, M.H. Abraham, R.A. McGill, P. Sasson, Determination of partition coefficients from surface acoustic wave vapor sensor responses and correlation with gas-liquid chromatographic paitition coefficients. Anal. Chem. 60, 869-875 (1988)... 

Schweizer-Berberich M, Strathmann S, Gopel W, Sharma R, Peyie-Lavigne A (2000) Filters for tin dioxide CO gas sensors to pass the UL2034 standard. Sens Actuators B 66 34-36 Shen CY, Huang CP, Huang WT (2004) Gas-detecting properties of surface acoustic wave ammonia sensors. Sens Actuators B 101 1—7... 

The adsorption and desorption isotherms of an inert gas (classically N2 at 77 K) on an outgassed sample are determined as a function of the relative pressure (Prei = p/Po/ the ratio between the applied pressure and the saturation pressure. The adsorption isotherm is determined by measuring the quantity of gas adsorbed for each value of p/po by a gravimetric or a volumetric method (less accurate but simpler). A surface acoustic wave device can also be used as a mass sensor or microbalance in order to determine the adsorption isotherms of small thin films samples (only 0.2 cm of sample are required in the cell) [42,43]. 

Surface acoustic waves (SAW), which are sensitive to surface changes, are especially sensitive to mass loading and theoretically orders of magnitude more sensitive than bulk acoustic waves [43]. Adsorption of gas onto the device surface causes a perturbation in the propagation velocity of the surface acoustic wave, this effect can be used to observe very small changes in mass density of 10 g/cm (the film has to be deposited on a piezoelectric substrate). SAW device can be useful as sensors for vapour or solution species and as monitors for thin film properties such as diffusivity. They can be used for example as a mass sensor or microbalance to determine the adsorption isotherms of small thin film samples (only 0.2 cm of sample are required in the cell) [42]. 

Chemical sensors for gas molecules may, in principle, monitor physisorp-tion, chemisorption, surface defects, grain boundaries or bulk defect reactions [40]. Several chemical sensors are available mass-sensitive sensors, conducting polymers and semiconductors. Mass-sensitive sensors include quartz resonators, piezoelectric sensors or surface acoustic wave sensors [41-43]. The basis is a quartz resonator coated with a sensing membrane which works as a chemical sensor. 

The amplitude density function of Surface Acoustic Wave (SAW) resonators or MOSFET sensor signals contains information about the number of adsorbed molecules. By measuring the amplitude density function and comparing it with the theoretical form, the concentration of the detected gas can be estimated. If sensor size is in the nanometer range, then the exact number of adsorbed molecules can be determined. Fignre 2 shows the result of computer simulations of the output signal of a nanoscale MOSFET sensor. 

Another important area where gold-thiol monolayers might find promising applications is gas- and biosensing. Simple sensors sensitive to certain types of compounds, based on such detection methods as surface plasmon resonance or surface acoustic wave, have been described454,455,531-533. This type of device is usually made of a gold plate coated with a functionalized monolayer. The terminal functional group of such a monolayer is responsible for selective interactions with the analyte, and adsorption of the latter is then detected by the appropriate method. 

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. 

Table 3. Some commercial companies that manufactured sensor-based electronic noses and related instruments in 2003. Key to sensor technologies MOS - metal oxide sensor, CP -conducting polymer, QMB - quartz crystal microhalance, FET - field effect transistor, SAW - surface acoustic wave key to analytical instruments MS - mass spectrometry, GC - gas chromatography, IMC - ion mobility cell...

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