Biblio

The main limitation of acoustic particle separation for microfluidic application is its low sorting efficiency. This is due to the weak coupling of surface acoustic waves (SAWs) into the microchannel. In this work, we demonstrate bulk acoustic wave (BAW) particle sorting using capacitive micromachined ultrasonic transducers (CMUTs) for the first time. A collapsed mode CMUT was driven in air to generate acoustic pressure within the silicon substrate in the in-plane direction of the silicon die. This acoustic pressure was coupled into a water droplet, positioned at the side of the CMUT die, and measured with an optical hydrophone. By using a beam steering approach, the ultrasound generated from 32 CMUT elements were added in-phase to generate a maximum peak-to-peak pressure of 0.9 MPa. Using this pressure, 10 µm latex beads were sorted almost instantaneously.

SummaryIn this study, the propagation and resonance properties of shear-horizontal surface acoustic waves (SH SAWs) on a rotated Y-cut 90°X propagating Ca3TaGa3Si2O14 (CTGS) with a Au- or Al-interdigital transducer (IDT) were investigated theoretically and experimentally. It was found that not only a high-density Au-IDT but also a conventional Al-IDT enables the energy trapping of SH SAW in the vicinity of the surface. For both IDTs, the effective electromechanical coupling factor of about 1.2% and the zero temperature coefficient of frequency can be simultaneously obtained by adjusting the cut angle of CTGS and the electrode film thickness.

Surface acoustic wave devices based on LiNbO3/interlayer/substrate layered structure have attracted great attention due to the high electromechanical coupling coefficient (K2) of LiNbO3 and the energy confinement effect of the layered structure. In this study, 30° YX-LiNbO3 (LN)/SiO2/Si multilayered structure, which can excited shear-horizontal surface acoustic wave (SH-SAW) with high K2, was proposed. The optimized orientation of LiNbO3 was verified by the effective permittivity method based on the stiffness matrix. The phase velocity, K2 value, and temperature coefficient of frequency (TCF) of the SH-SAW were calculated as a function of the LiNbO3 thickness at different thicknesses of the SiO2 in 30° YX-LiNbO3/SiO2/Si multilayer structure by finite element method (FEM). The results show that the optimized LiNbO3 thickness is 0.1 and the optimized SiO2 thickness is 0.2λ. The optimized Al electrode thickness and metallization ratio are 0.07 and 0.4, respectively. The K2 of the SH-SAW is 29.89%, the corresponding phase velocity is 3624.00 m/s and TCF is about 10 ppm/°C with the optimized IDT/30° YX-LiNbO3/SiO2/Si layered structure.

This paper reports high frequency surface acoustic wave (SAW) devices developed on Sc doped (30%) AlN on high resistivity Si for demonstrating surface acoustic wave – spin wave coupling. Enhanced Q-factors were found for both propagation modes – Rayleigh (4.7 GHz) and Sezawa (8 GHz). SAW/SW (spin wave) coupling is proven for two-ports SAW structures having a magnetostrictive layer of Ni between the two interdigitated transducers (IDTs). A decrease of 3.42 dB was observed in the amplitude of the transmission parameter, at resonance, when the magnetic field was applied. The angle between the applied magnetic field and the SAW propagation direction is π/4.

This paper is the first to investigate the long-term stability of Surface Acoustic Wave Gyroscopes (SAWG) using an ovenized control system. Monolithic integration of a MEMS heater adjacent to SAW devices on Lithium Niobate over insulator substrate (LNOI) tightly couples frequency-based temperature detection with heating for temperature and frequency stabilization. This first prototype demonstrates the ability to minimize the temperature variations of the SAWG to below ±10 μK and stabilize the SAWG resonance frequency to ±0.2 ppm. This approach thus eliminates the thermal drift in a SAWG and enables the development of a new generation of MEMS-based gyroscopes with long-term stability.

This paper proposes a method to synthesis acoustic wave (AW) filters with Chebyshev response automatically. Meanwhile, each AW resonator used to design the filter can be easily fabricated on the same piezoelectric substrate. The method is based on an optimization algorithm with constraints for constant electromechanical coupling coefficient ( kt2) to minimize the defined cost function. Finally, the experimental result for a surface acoustic wave (SAW) filter of global positioning system (GPS) frequency band based on the 42° lithium tantalate (LiTaO3) substrate validates the simulation results. The designed filter shows insertion loss (IL) and return loss (RL) better than 2.5dB and 18dB respectively in the pass-band, and out-band reflection larger than 30dB.

The security of an organization lies not only in physical buildings, but also in its information assets. Safeguarding information assets requires further study to establish optimal security mitigation steps. In determining the appropriate mitigation of information assets, both an information security risk assessment and a clear and measurable rating are required. Most risk management methods do not provide the right focus on ranking the critical information assets of an organization. This paper proposes a framework approach for ranking critical information assets. The proposed framework uses the OCTAVE Allegro method, which focuses on profiling information assets by combining ranking priority measurements using decision support system methods, such as Simple Additive Weighting (SAW) and Analytic Hierarchy Process (AHP). The combined OCTAVE Allegro-SAW and OCTAVE Allegro-AHP methods are expected to better address risk priority as an input to making mitigation decisions for critical information assets. These combinations will help management to avoid missteps in adjusting budget needs allocation or time duration by selecting asset information mitigation using the ranking results of the framework.

Surface acoustic wave (SAW) optical sensor based on two-dimensional (2D) sensing layer can always provide extremely high sensitivity. As an attractive option, the application of exfoliated 2D perovskite on acousto-optic coupling optical sensor is investigated. In this work, exfoliated 2D (PEA)2PbI4 sheet was transferred as a sensing layer onto the delay area of a dual-port SAW resonator with resonant frequency 497 MHz. From the response under 532 nm laser with intensity of 0.9 mW/cm2, a largest frequency shift of 13.92 MHz was observed. The ultrahigh sensitivity up to 31.6 ppm/(μW/cm2) was calculated by experiment results. We also carried out theoretical analysis and finite element simulation of 3D model to demonstrate the mechanism and validity for optical sensing. The fabricated optical sensor expressed great potential for a variety of optical applications.

According to the technical difficulties of the air-coupled piezoelectric ultrasonic transducer, 1-3 type piezoelectric composites and double matching layers structure are adopted in order to solve the acoustic impedance mismatch at the interface between the piezoelectric materials and air. The optimal design of the matching layer thickness for double matching layers structure air-coupled ultrasonic transducer is also completed through experiments. Based on this, 440 kHz flat-plate and focused air-coupled piezoelectric ultrasonic transducer are designed, fabricated and characterized. Finally, surface cracks are detected using the focused air-coupled piezoelectric ultrasonic transducer.

We investigate directional differences when coupling Lamb waves in a structure to guided modes in an optical fiber sensor for detection of the ultrasonic wave propagation through the structure.

A new class of multi-band acoustic-wave-Iumped-ele-ment-resonator (AWLR)-based bandstop filters (BSFs) is reported. It is based on\$N\$multi-resonant A WLRs-shaped by\$K\$AWLRs and 2K inverters-that are connected to an all-pass network and result in\$\textbackslashtextbackslashpmbK\textbackslashtextbackslash Nˆth\$order rejection bands. The proposed concept allows the realization of multiple rejection bands with the following characteristics: i) fractional bandwidths (FBWs) larger than the electromechanical coupling coefficient\$\textbackslashtextbackslashpmbk\_tˆ\textbackslashtextbackslash 2\$of its constituent acoustic-wave resonators, ii) continuously variable and inde-pendently-controlled FBWs, iii) intrinsically-switched stopbands, and iv) an all pass state. For proof-of-concept validation purposes a dual-band prototype was designed, built, and tested. It exhibits two stopbands centered at 418 and 433 MHz that can be continu-ously-tuned in FBW (up to 7.7:1 tuning range) and in number.

We report time-domain measurements of acoustic-wave-induced magnetization dynamics in magnetic tunnel junctions. The acoustic pulses are generated by femtosecond laser excitation and interact with the magnetization through magnetoelastic coupling. The induced magnetization precession is not only dependent on the externally applied magnetic field, but also on the laser excitation position. The presented method even allows us to coherently control the precession using two laser pulses at various magnetic fields and excitation positions.