SAW Chemical Sensor

Sample Adsorption of Chemicals om the Vapor Sample Changes of Surface 

Desorption of Chemicals from the SAW Surface and Ready for Next Sample 

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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). 

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.

Ricco A.T. 1994. SAW Chemical sensors. The Electrochemical Society Interface Winter 38-44. 

Penza M, Antolini F, Vittori-Antisari M (2004a) Carbon nanotubes as SAW chemical sensors materials. Sens Actuators B 100 47-59... 

Piezoelectric transducers have been applied to a wide variety of mass and chemical measurement applications. Bulk wave devices have been used for analytical measurements since the 1960s. Several reviews of their use have been published by Guilbault (33, 34), and a more recent and fairly comprehensive review has been written by Alder and McCallum (35). Applications involving SAW devices first appeared in 1979 (36, 37). Reviews of SAW sensor design have been published by Wohltjen (31) and Venema (25), and the surface chemistry of SAW chemical sensors has been discussed by Nieuwenhuizen (38). Most recently an issue of IEEE Transactions on Ultrasonics has been devoted to a review and discussion of acoustic sensor applications (84). 

Figure 48. Various possible sensor configurations for SAW chemical sensors [230]...

Bulk and surface imprinting strategies are straightforward tools to generate artificial antibodies. Combined with transducers such as QCM (quartz crystal microbalance), SAW (surface acoustic wave resonator), IDC (interdigital capacitor) or SPR (surface plasmon resonator) they yield powerful chemical sensors for a very broad range of analytes. 

Surface acoustic wave (SAW)-type chemical sensors exploit the propagation loss of the acoustic waves along layered structures consisting of at least a substrate covered by the CIM. 

There are certain aspects of performance that make the Apm oscillators potentially attractive as chemical sensors. First of all, the fact that both surfaces contribute to the signal means that the sensitivity is higher than for the corresponding SAW device. The most important advantage follows from the fact that velocity of the lowest order of the antisymmetric mode is much slower than the compressional velocity of sound in most liquids (900-1,500 m s-1), which means that the energy... 

There are several applications of ZnO that are due to its excellent piezoelectric properties [28,164]. Examples are surface-acoustic wave (SAW) devices and piezoelectric sensors [28,165-167]. Typically, SAW devices are used as band pass filters in the tele-communications industry, primarily in mobile phones and base stations. Emerging field for SAW devices are sensors in automotive applications (torque and pressure sensors), medical applications (chemical sensors), and other industrial applications (vapor, humidity, temperature, and mass sensors). Advantages of acoustic wave sensors are low costs, ruggedness, and a high sensitivity. Some sensors can even be interrogated wirelessly, i.e., such sensors do not require a power source. 

The addition of mass provides the means of transduction for many chemical sensors, including surface acoustic wave (SAW) devices, quartz crystal microbalances (QCM), and microcantilevers. In all these devices, the mass addition either perturbs the vibration, oscillations, or deflection within the transducer. The mode of transduction in an optical interferometer can also be linked to mass addition the sensor s response is altered by refractive index changes in the material being monitored. It is possible that this change can be elicited solely from refractive index changes without the addition of mass, although in sensing a particular... 

Integrated Chemical Sensors Corp. 90 Oak St. Newton, MA 02164 SAW systems... 

The instrumental basis of chemical sensing has been extensively explored. Several methods have become favoured due to their ease of operation, sensitivity or cost. These methods are usually based on optics, resistance, capacitance or SAWS. All of these methods share one distinct problem, the need for chemical selectivity. Most of the accounts describing chemical sensors end with a statement that suggests other sensors could be fabricated similarly, if only a chemical recognition unit were... 

Chemosensory applications will normally take place in an environment of complex composition. Humidity and other varying ambient conditions are in sharp contrast to the well-defined environment most typically found in related applications of imprinted polymers. Moreover, the trend in sensor technology towards miniaturisation, with the aim of future nano-scale dimensions, is a primary reason for rising perturbation sensitivity, such as new interfering forces that can be neglected in the macro range. Chemical sensors can be influenced by numerous factors, such as electrostatic effects (ChemFETs) or non-specific adsorption (SAW, surface plasmon resonance). 

Wohltjen, H., Jarvis, N.L., and Lint, J.R., 1991. Surface acoustic-wave (SAW) chemical microsensors and sensor arrays for industrial-process control and pollution prevention, Abstr. Papers Am. Chem. Soc. (ENVR.) 201, pp. 63-66. 

Compact chemical sensors can be broadly classified as being based on electronic or optical readout mechanisms [28]. The electronic sensor types would include resistive, capacitive, surface acoustic wave (SAW), electrochemical, and mass (e.g., quartz crystal microbalance (QCM) and microelectromechanical systems (MEMSs)). Chemical specificity of most sensors relies critically on the materials designed either as part of the sensor readout itself (e.g., semiconducting metal oxides, nanoparticle films, or polymers in resistive sensors) or on a chemically sensitive coating (e.g., polymers used in MEMS, QCM, and SAW sensors). This review will focus on the mechanism of sensing in conductivity based chemical sensors that contain a semiconducting thin film of a phthalocyanine or metal phthalocyanine sensing layer. 

Keywords Mass-sensitive transducer QCM SAW Molecular imprinting Chemical sensor... 

Polymer films have been very widely applied to modify the surfaces of chemical sensors both for solution and gas phase measurements. Solution coating has been used to coat quartz crystal oscillators [91-93, 112] and SAW devices [113, 114] with various polymeric adsorbates and polymer/lipid mixtures [90, 94] to prepare arrays of sensors for use in gas sensing and odor evaluation and discrimination. 

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