Analysis of longitudinal leaky surface acoustic waves on quartz thin plate bonded to similar-material substrate

The propagation and resonance properties of longitudinal leaky surface acoustic waves (LLSAWs) on bonded structures consisting of a quartz (Qz) thin plate and a Qz support substrate with different Euler angles were investigated theoretically. By using both an X-cut Qz thin plate and a Qz support substrate with optimal Euler angles, we obtained LLSAWs with a larger coupling factor, a smaller attenuation, and a lower temperature coefficient of frequency than those on a single Qz substrate. Furthermore, from the resonance properties simulated by the finite element method, the bonded structures were found to exhibit a large admittance ratio and a high quality factor, which could not be obtained when using a single Qz substrate; the bandwidth however was as small as 0.016-0.086%.

Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Gas-Coupled Laser Acoustic Detection (GCLAD) is an ultrasonic, non-contact detection technique that has been recently proven to be applicable to the inspection of mechanical components. GCLAD response raises as the intersection length between the probe laser beam and the acoustic wavefront propagating in the air increases; such feature differentiates the GCLAD device from other optical detection instruments, making it a line detection system rather than a point detector. During the inspection of structures mainly extending in two dimensions, the capability to evidence presence of defects in whichever point over a line would enable moving the emitter and the detector along a single direction: this translates in the possibility to decrease the overall required time for interrogation of components compared to point detectors, as well as generating simpler automated monitoring layouts. Based on this assumption, the present study highlights the possibility of employing the GCLAD device as a line inspection tool. To this end, preliminary concepts are provided allowing maximization of the GCLAD response for the non-destructive testing of components which predominantly extend in two dimensions. Afterwards, the GCLAD device is employed in pulse-echo mode for the detection of artificial defects machined on a 12 mm-thick steel plate: the GCLAD probe laser beam is inclined to be perpendicular to the propagation direction of the airborne ultrasound, generated by surface acoustic waves (SAWs) in the solid which are first reflected by the defect flanks and subsequently refracted in the air. Numerical results are provided highlighting the SAW reflection patterns, originated by 3 mm deep surface and subsurface defects, that the GCLAD should interpret. The subsequent experimental campaign highlights that the GCLAD device can identify echoes associated with surface and subsurface defects, located in eight different positions on the plate. B-scan of the component ultimately demonstrates the GCLAD performance in accomplishing the inspection task.

Analysis of propagation characteristics of Rayleigh surface acoustic waves on Yb0.33Al0.67N piezoelectric films/high-velocity substrates

Piezoelectricity of YbAlN films has recently been shown to be almost as high as that of ScAlN films. YbAlN film surface acoustic wave (SAW) resonators are expected to have a high coupling factor. We theoretically investigated the propagation characteristics of first-mode Rayleigh SAWs (RSAWs) on Yb0.33Al0.67N film/high-velocity Si, sapphire, AlN, SiC, BN, and diamond substrates. The first-mode RSAWs on the YbAlN layered structures had high coupling factors, higher than those on ScAlN layered structures. An enhancement of the effective coupling factor of the first mode RSAWs was observed in polarity inverted YbAlN film/BN or diamond substrate structures.

Optimizing the Design of Surface-Acoustic-Wave Ring Resonator by Changing the Interdigitated Transducer Topology

Introduction. Previous works considered the frequency characteristics and methods for fixing sensitive elements in the form of a wave ring resonator on surface acoustic waves in a housing made of various materials, as well as the influence of external factors on sensitive elements. It was found that the passband in such a case is sufficiently wide, which can affect adversely signal detection when measuring acceleration using the sensitive element under development. Therefore, it has become relevant to reduce the sensitive element’s bandwidth by changing the design of the interdigitated transducer (IDT).Aim. To demonstrate an optimal topology for an IDT with a low bandwidth, leading to improved signal detection when acceleration affects the sensitive element.Materials and methods. The finite element method and mathematical processing in AutoCAD and in COMSOL Multiphysics.Results. Nine topologies of IDT are proposed. All these types were investigated using the COMSOL Multiphysics software on lithium niobate substrates, which material acts as a sensitive element. The frequency characteristics are presented. The data obtained allowed an optimal design of the ring resonator to be proposed: an IDT with rectangular pins without selective withdrawal.Conclusion. Self-generation in a ring resonator can be performed by withdrawing no more than one pair of IDTs for 10 or more periods. In this case, the withdrawal of IDTs should be uniform. With an increase in the number of IDT withdrawals, the geometry of the ring resonator is violated, and the wave leaves the structure. The presence of a shared bus keeps the surface acoustic wave inside the IDT structure, and the narrowing of the periods towards the inner part of the structure makes it possible to improve the frequency characteristics of the ring resonator on surface acoustic waves.

Current Development in Interdigital Transducer (IDT) Surface Acoustic Wave Devices for Live Cell In Vitro Studies: A Review

Acoustics have a wide range of uses, from noise-cancelling to ultrasonic imaging. There has been a surge in interest in developing acoustic-based approaches for biological and biomedical applications in the last decade. This review focused on the application of surface acoustic waves (SAW) based on interdigital transducers (IDT) for live-cell investigations, such as cell manipulation, cell separation, cell seeding, cell migration, cell characteristics, and cell behaviours. The approach is also known as acoustofluidic, because the SAW device is coupled with a microfluidic system that contains live cells. This article provides an overview of several forms of IDT of SAW devices on recently used cells. Conclusively, a brief viewpoint and overview of the future application of SAW techniques in live-cell investigations were presented.