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Transducers
Published in Anton F. P. van Putten, Electronic Measurement Systems, 2019
Surface acoustic wave (SAW) transducers are able to convert an electrical signal at the input into an acoustic signal and at the output to convert it again into an electrical signal. The generated waves can propagate at a more or less elastic surface. The amplitude is attenuated exponentially with the penetration depth. For this type of transducer the only relevant type of wave is a wave in a Rayleigh mode. The waves are characterized by their specific mode, where their mechanically and electrically equivalent components lie in one plane perpendicular with respect to the surface. Characteristics of Rayleigh waves are as follows: waves can be modulated at the surfacethe technology for SAWs is compatible with planar technologybandwidth ranges from 20 MHz to 2 GHza piezoelectric substrate is required to generate Rayleigh waves.
Passive Radio-Frequency Acoustic Sensors and Systems for Wired and Wireless Applications
Published in Vikas Choudhary, Krzysztof Iniewski, MEMS, 2017
Sylvain Ballandras, Gilles Martin, Jean-Michel Friedt, Victor Plessky, Virginie Blondeau-Pâtissier, William Daniau, Thomas Baron, Luc Chommeloux, Stéphane Tourette, Jean-François Leguen, Bruno François, Christophe Droit, Meddy Vanotti, Marc Lamothe, David Rabus, Nicolas Chrétien, Emile Carry
Several piezoelectric materials can potentially be used for the fabrication of SAW sensors, the most used still being quartz (although SAW filters are mainly based on lithium tantalate). This material actually allows for the sensor property optimization by a proper choice of the crystal cut angles and propagation direction according to the given requirements and specifications. Furthermore, the existence of a wide range of piezoelectric materials enables one to develop innovative solutions for numerous applications; for instance, by taking advantage of the large electromechanical coupling of LiNbO3 or the capability of given orientations to excite pure modes (longitudinal and shear) trapped at the substrate surface by proper transducer structures. Table 19.1 shows a collection of materials and related crystal orientations widely used for SAW application and therefore usable for SAW sensor developments according to their specific properties.
Application of Rapid Manufacturing to build artifacts for using in microgravity environment. An International Space Station case
Published in Paulo Jorge Bártolo, Artur Jorge Mateus, Fernando da Conceição Batista, Henrique Amorim Almeida, João Manuel Matias, Joel Correia Vasco, Jorge Brites Gaspar, Mário António Correia, Nuno Carpinteiro André, Nuno Fernandes Alves, Paulo Parente Novo, Pedro Gonçalves Martinho, Rui Adriano Carvalho, Virtual and Rapid Manufacturing, 2007
I.A. Maia, M.F. Oliveira, P.Y. Noritomi, J.V.L. Silva
The protein clouds were obtained by atomization of protein solutions using a SAW (Surface Acoustic Waves) device, specially built to perform the atomization function in a very efficient manner. The SAW device is a transductor that converts electricity into mechanic waves on the surface of a piezoelectric material. Although the chemical reaction is the core issue of the experiment and the construction of the SAW device is a very relevant point in the experimental set up they are out of the scope of the present work. Here only the aspects concerning rapid manufacturing are taken into consideration as study of case of applications of RM in scientific experiments.
Use of Surface Acoustic Wave (SAW) for Thermal Conductivity Sensing of Gases – a Review
Published in IETE Technical Review, 2021
Fahim Durani, Upendra Mittal, Jitender Kumar, A.T. Nimal
A SAW device essentially consists of a piezoelectric substrate and metallic comb-like structure called Interdigital Transducer (IDT) deposited on the substrate [57]. Schematic of a typical SAW device is shown in Figure 2. IDT converts the applied electrical signal into acoustic mechanical waves and back to electrical signal. Different types of acoustic waves are possible depending on the crystal cut; however, Rayleigh Wave is most commonly used for gas sensing because it is easy to generate [46]. The acoustic wave generated propagates at a typical velocity of 10−5 times velocity of light and is mostly restricted to the surface of the substrate [54]. The high energy density at the surface of the device substrate is thus a fundamental feature for very high sensitivity of SAW sensors. The change in the environmental parameters such as temperature and pressure etc. can change the characteristics of surface acoustic wave like velocity and attenuation which, in turn, results in change in phase and delay in SAW device [58]. This property is exploited in realizing physical sensor in SAW.
Anti-plane shear wave motion in a composite layered structure with slit
Published in Waves in Random and Complex Media, 2021
Juhi Baroi, Sanjeev A. Sahu, Sonal Nirwal
The study of surface waves in composite structures with air gap has been of interest for many engineers due to its tremendous application in the fields of resonators, wireless sensors, transducers, etc. [29–31]. As air can produce electric fields, this allows to use air as gap of finite width in several piezoelectric devices for range of applications. The electric fields in the air gap can interact with the acoustic fields of different composite and piezoelectric materials. The acoustic wave devices and electro-mechanical systems are designed in combination with air gap in such a way that it can store the maximum acoustic energy within the structure. Inducing gas in such devices can help to detect differences in the density of the system and acoustic velocity changes as well as mass changes which enable multi-sensing and this feature makes the system adequate for particular gas sensing. In wireless system, radio frequency (RF) filters play a key role. High-performance RF filters can be achieved by SAW devices at low cost. At higher frequency range, the SAW structure fails to work for certain applications. Considering air gap makes such or similar structures capable to perform at large frequencies at an efficient low cost in comparison with SAW devices. These factors set the motivation for the present study. Up to now, no attempt has been made to study the propagation of anti-plane waves in an FGPM/piezoelectric substrate separated by a finite gap layer.
Microstructural and viscous liquid loading effects on the propagation of love waves in a piezomagnetic layered structure
Published in Mechanics of Advanced Materials and Structures, 2021
Piezomagnetic (PM) materials are those which exhibit a magnetic field under the action of mechanical stress. In PM materials the physical deformation and the induction of magnetic moment in the presence of stress are produced by applying a magnetic field. Immense applications in the configuration of Surface Acoustic Wave (SAW) devices, transducers, Love wave sensors and other similar types of devices are perceived by the surface wave propagation in a stratified structure comprising of PM layer followed by a semi-infinite substrate. These structures received considerable attention from many researchers owing to their relevance in many branches of engineering and applied sciences. A surface acoustic wave (SAW) is an acoustic wave that propagates along the surface of a material and exhibits elasticity with an amplitude that decays exponentially with depth into the substrate. Some significant works to feature the surface wave behavior in PM structure have been carried out in the recent past (Ezzin et al. [1, 2]). Alshits et al. [3] analyzed the existence of surface waves in half-infinite anisotropic elastic media with PM properties. A theoretical study of SH-wave propagation in a periodically layered PM structure was carried out by Liu et al. [4]. Nie et al. [5] have investigated the propagation of shear horizontal waves in layered piezoelectric/piezomagnetic coupled plates. Sahu and Baroi [6] analyzed surface wave behavior in corrugated PM layer resting on inhomogeneous half-space.