SAW-based sensors

SAWs are well suited for either fixed or wireless sensor applications as the specific sensor constituent to be measured typically varies one or more of the SAW s physical parameters. Surface acoustic wave (SAW) based sensors and sensor systems have following advantages ... 

The fundamental parameters controlling operating characteristics of SAW-based sensors are the SAW velocity, the temperature coefficients of delay (TCD), the electromechanical coupling factor, and the propagation loss. In SAW applications, the coupling factor relates to the maximum bandwidth obtainable and the amount of signal loss between input and output that determines the fractional... 

Table L Chemically Sensitive Films and Analytes for SAW-Based Sensors...

Polycyclic aromatic hydrocarbons (PAHs) in water Phloroglucinol and triisocyanate MEP-based sensors (QCM, SAW and optical transducers) 30 ng/L (ppt level) Dickert et al., 1999... 

Nieuwenhuizen, M.S and Nederlof, A.J., A silicon-based SAW chemical sensor for NO2 by applying a silicon nitride passivation layer, Sens. Actuators, B, 9, 171 (1992). 

Temperature effects on coating response behavior are varied. For reversible equilibrium-based sensors, increased temperature results in decreased sensitivity. An example of this tonperature-dependent response behavicM- is provided in Figure S.4 for a PIB-coated SAW device exposed to dichloroediane (DCE) vapor. From Figure 5.4(a) it can be seen that the response (in Hz) increases steadily as the concoitration of DCE increases, but that the sltqte of the response curve decreases with increasing temperature. This decreased sensitivity is due to the Arrhenius-type decrease in the equilibrium constant, K (see Sections 5.4.1 and... 

Most immunochemically based sensors to date have been developed for liquid-phase measurements thus, the TSM resonator has been the device of choice. Of course, other plate-mode devices (SH-APM, FPW) would be equally well suited for liquid-phase detection and may have advantages in terms of sensitivity. A low-frequency (20 MHz) SAW liquid-phase immunoassay device has been reported [27], but operation of SAWs of higher frequencies in liquids is not feasible due to excessive attenuation of the SAW by the liquid. An alternative to in-situ detection is to expose a protein-coated AW device to a liquid-phase sample for a period of time, then dry it [226] the observed frequency shift is proportional to analyte concentration. When using this technique, it is crucial that careful control experiments in the absence of analyte be performed to obtain an accurate idea of the reproducibility of the baseline oscillation frequency throughout the procedure. 

SAW-based CW-agent point-sensor concept that is being incorporated into the... 

An example of one of TSA/TSL s R D funded MEMS based project is the Sandia National Laboratories (SNL) MicroHound project. This is based on the SNL Micro Chem Lab on a Chip , illustrated in Figure 1. The original prototype system from SNL was developed for high vapour pressure, chemical weapons (CW) detection, which utilized a MEMS GC separator, with miniature surface acoustic wave (SAW s) based sensors. The system included an inlet, coated pre-concentrators, detectors, and pumps. To make this useful for trace explosives detection, the addition of an alternate front-end sample collection/macro-preconcentrator and MEMS based coated-preconcentrator is necessary, along with the option to utilize or exclude the MEMS GC separator followed by detection by either, or both, SAW s and miniaturized IMS detectors. 

SAW chemical sensors are based on the effects of adsorbed molecules on geometrical, elastic and electric properties of gas-sensing layer and corresponding mass-loading of the working surface of the substrate carrying SAW (Fig. 1). 

Figure 1. SAW chemical sensor with CNT array based sensing element and acoustic and electric output signal.

Nieuwenhuizen MS, Harteveld JLN (1994) An automated SAW gas sensor testing system. Sens Actuators A 44 219-229 Oprea A, Weimar U, Simon E, Fleischer M, Frerichs H-P, WUbertz C, Lehmann M (2006) Copper phthalocyanine suspended gate field effect transistors for NOj detection. Sens Actuators B 118 249-254 Ozturk ZZ, Kilinc N, AtillaD, Gurek AG, Ahsen V (2009) Recent studies of chemical sensors based on phthalocytmines. 

Low-temperature sensors surface plasmon resonance sensors pellistors biosensors High-temperature electrochemical gas sensors sensors for tough conditions electronic nose RT electrochemical sensors Membranes filters for aU types of sensors SAW sensors cantilever-based sensors... 

Low-temperature sensors SAW sensors biosensors humidity sensors conductometric gas sensors membranes electrochemical sensors cantilever-based sensors optical and fiber-optic sensors electronic noise... 

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