Thickness-shear-mode acoustic wave

Quartz crystal microbalance — The quartz crystal microbalance (QCM) or nanobalance (QCN) is a thickness-shear-mode acoustic wave mass-sensitive detector based on the effect of an attached foreign mass on the resonant frequency of an oscillating quartz crystal. The QCM responds to any interfacial mass change. The response of a QCM is also extremely sensitive to the mass (density) and viscoelastic changes at the solid-solution interface [i-vi]. 

Yang, M. Thompson, M., Multiple chemical information from the thickness shear mode acoustic wave sensor in the liquid phase, Anal. Chem. 1993, 65, 1158-1168... 

Thompson M., Kipling A. L., Duncan-Hewitt W. C., Rajakovic L. V., and Cavic B. A., Thickness shear-mode acoustic wave sensors in the liquid phase. Analyst, 116, 881-890, 1991. 

Other theoretical approaches relevant to applications in the gas phase and dealing with thickness-shear mode acoustic wave quartz sensors are presented in [213], [232]-[237],... 

Thickness shear mode Acoustic surface waves Acoustic plate mode... 

A piezoelectric mass sensor is a device that measures the amount of material adsorbed on its surface by the effect of the adsorbed material on the propagation of acoustic waves. Piezoelectric devices work by converting electrical energy to mechanical energy. There are a number of different piezoelectric mass sensors. Thickness shear mode sensors measure the resonant frequency of a quartz crystal. Surface acoustic wave mode sensors measure the amplitude or time delay. Flexure mode devices measure the resonant frequency of a thin Si3N4 membrane. In shear horizontal acoustic plate mode sensors, the resonant frequency of a quartz crystal is measured. 

A quartz crystal sensor chip was bonded with a microfluidic glass chip for acoustic wave detection (see Figure 7.46). The sensor was operated in the thickness-shear mode (TSM). This has allowed rat heart muscle cell contraction to be studied based on the measurement of the resonant frequency changes [133]. 

First, the underlying principles upon which bulk acoustic wave (BAW) devices operate are described. When a voltage is applied to a piezoelectric crystal, several fundamental wave modes are obtained, namely, longitudinal, lateral and torsional, as well as various harmonics. Depending on the way in which the crystal is cut, one of these principal modes will predominate. In practice, the high-frequency thickness shear mode is often chosen since it is the most sensitive to mass changes. Figure 3.4 schematically illustrates the structure of a bulk acoustic wave device, i.e. the quartz crystal microbalance. 

Note that the source tenn is non-zero only in regions where it varies spatially. This is an important consideration in the mechanism by which acoustic waves are launched in the thickness-shear mode resonators that we consider later. 

Devices based on piezoelectric crystals, which allow transduction between electrical and acoustic energies, have been constructed in a number of conrigurations for sensor applications and materials characterization. This cluqtter examines those devices most commonly utilized for sensing a( licatithickness-shear mode (TSM) resonator, the surface acoustic wave (SAW) device, the acoustic plate mode (APM) device, and the flexural plate wave (FPW) device. Each of these devices, shown schematically in Figure 3.1, uses a unique acoustic mode. 

Figure 3.1 Schematic sketches of the four types of acoustic sensors, (a) Thickness-Shear Mode (TSM) resonator (b) Surface-Acoustic-Wave (SAW) sensor, (c) Shear-Horizontal Acoustic-Plate-Mode (SH APM) sensor, and (d) Flexural-Plate-Wave (FPW) sensor.

Fig. 8 Idealised model of acoustic attenuation. A Diagrammatic representation of a thickness shear mode bulk acoustic wave resonator, coated with a rigid metal adhesion and electrode layer, a rigid chemical linker layer, a finite viscoelastic antibody receptor layer, a second adherent finite viscoelastic analyte layer, and finally a Newtonian liquid. B An idealised model of acoustic attenuation from bulk quartz through the above layers of varying viscosity, density, and shear modulus...

QCM can be described as a thickness-shear mode resonator, since weight change is measured on the base of the resonance frequency change. The acoustic wave propagates in a direction perpendicular to the crystal surface. The quartz crystal plate has to be cut to a specific orientation with respect to the ciystal axis to attain this acoustic propagation properties. AT-cut crystals are typically used for piezoelectric crystal resonators[7]. The use of quartz crystal microbalances as chemical sensors has its origins in the work of Sauerbrey[8] and King [9] who... 

J.W. Grate, S.N. Kaganove, V,R, Bhethanabotla Examination of mass and modulus contributions to thickness shear mode and surface acoustic wave vapour sensor responses using partition coefficients. Pp. 259-83. 

In this review, we discuss the development and appUcation to electrochemical problems of a bulk acoustic wave device, the thickness shear mode (TSM) resonator, whose operation (in the simplest case of a... 

Quartz is a well-known piezoelectric material. a-Quartz belongs to the triclinic crystal system with point group 32 and has a phase transition at 537°C to its P-form, which is not piezoelectric. Quartz has a cut with a zero temperature coefficient. For instance, quartz oscillators, operated in the thickness shear mode of the AT-cut, are used extensively for clock sources in computers, frequency stabilized ones in TVs and VCRs. On the other hand, an ST-cut quartz substrate with X-propagation has a zero temperature coefficient for surface acoustic wave and so is used for SAW devices with high-stabilized frequencies. The another distinguished characteristic of quartz is an extremely high mechanical quality factor Qm >10. ... 

If the wave propagates through the substrate, the wave is called a bulk wave. The most commonly used BAW devices are the thickness shear mode (TSM) resonator and the shear-horizontal acoustic plate mode (SH-APM) sensor. The TSM, also widely referred to as a quartz crystal microbalance (QCM), is the best-known and simplest... 

Generally, the cut angle of quartz crystal determines the mode of induced mechanical vibration of resonator. Resonators based on the AT-cut quartz crystal with an angle of 35.25° to the optical z-axis would operate in a thickness shear mode (TSM) (Fig. 1.1) [4]. Clearly, the shear wave is a transverse wave, that is, it oscillates in the horizontal direction (jc-axis) but propagates in the vertical direction (y-axis). When acoustic waves propagate through a one-dimensional medium, the wave function (ij/) can be described by [11] ... 

If an electric held of the proper frequency is applied across the quartz crystal, the crystal wiU oscillate in a mechanically resonant mode. These condihons correspond to the creation of a standing acoustic shear wave that has a node midpoint between the two faces of the crystal and two antinodes at both faces of the disk. This is depicted schematically in Eig. 21.20b. In an EQCM experiment the crystals are operated at the fundamental resonant frequency that is a function of the thickness of the crystal. A crystal with a thickness of 330pm has a resonant frequency of 5 MHz. Crystals with these characteristics are commercially available. In an EQCM experiment, an alternating electric field of 5 MHz is applied to excite the quartz crystal into... 

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