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A Love wave sensor with a phononic parylene-C wave guiding layer is proposed to detect the VEGF secreted during the selective platelet activation process, where arrays of a different material (filling material) are fabricated in the parylene-C films. The effects of the structural design parameters (period width and period number) on the electric response of sensors are investigated. As the period...
Acoustic streaming effects are usually treated using perturbation theory by writing the field variables as perturbation expansions utilizing a small scale parameter and solving the ensuing equation systems. When conducting numerical simulations, this approach can help reducing the computational effort drastically. In most cases, the zero-order velocity is assumed to be zero, which is an applicable...
Over the last decade, clinical studies show a strong interest for real-time 3D imaging. This calls for ultrasound probes with high-element-count 2D matrix transducer array, interfaced to an imaging system using an in-probe Application Specific Integrated Circuit (ASIC) that takes care of element selection, signal amplification, sub-array beamforming, etc. Since the ASIC is based on silicon and is...
This paper introduces the use of artificial neural networks (ANNs) as a method to guide the design of high-performance MEMS resonators and applies it to the prediction of spurious modes (SMs) in the proximity of the series resonance of aluminum nitride (AlN) contour-mode MEMS resonators (CMRs). ANN enables both fast and accurate prediction of spurious modes, hence facilitating the MEMS designer in...
Carotid plaque vulnerability is difficult to characterize from B-mode ultrasound imaging alone. However, elastographic characterization of plaque mechanical properties may aid in the assessment of vulnerability. As an initial step to understand the complex wave propagation that can occur in plaques, we have developed simulation models that incorporate different shear moduli (μ) of the arterial wall,...
Suppression of the SH-SAW response is mandatory to design TC SAW devices on θ degree rotated Y-cut LiNbO3. However, it is not easy because K2 for SH SAW changes rapidly with θ, and its optimal value in terms of the SH-SAW suppression is dependent on electrode and SiO2 thicknesses. The authors found that the optimal θ always locates close to θ where difference in velocities of two SAWs is minimum....
“Acoustic angiography” is a super-harmonic contrast imaging technique, which is based on the fact that when excited with a moderate acoustic pressure near their resonance (2–4 MHz; around MI of 0.5–0.7) ultrasound contrast agents produce broadband content which extends well past 15 MHz. By detecting the higher order harmonic energy while transmitting at a low fundamental frequency, exquisite resolution...
In the present work, nonlinearities in temperature compensating (TC) SAW devices are investigated. The materials used are LiNbO3-rot128YX as the substrate and Copper electrodes covered with a SiO2-layer as the compensating layer. In order to understand the role of these materials for the nonlinearities in such acoustic devices, a FEM simulation model in combination with a perturbation approach [1]...
Novel methods for determining rupture risk in abdominal aortic aneurysms (AAAs) have focused primarily on CT-based wall stress analysis using finite element models (FEMs). Recent studies have demonstrated ultrasound (US) based FEM, and the possibility of using inverse FEM analysis: matching displacements between the models and US to find patient specific aortic stiffness. This requires an accurate...
Treatment outcomes for esophageal cancer can be significantly improved through early detection. Endoscopy, with or without fluorescence, as well as micro-ultrasound (μUS) have been explored as methods to detect the epithelial cell patterns associated with Barrett's esophagus (BE), a precursor to esophageal cancer. In addition, a characteristic microvascular pattern is associated with high grade dysplasia...
The resonance frequency of an active element in a piezoelectric ultrasonic transducer is dependent on its length scale. Inspired by natural occurring auditory systems, incorporation of elements with varying length scales in the piezoelectric transducer design can result in a wider operational bandwidth. In this paper, a mathematical algorithm was developed first to define the feature of a fractal...
Design of side edges is one of the most important tasks for realization of high performance RF SAW/BAW devices. For the purpose, the authors proposed an FEM based technique where the specified mode is injected to the border under concern through a damping mechanism, and scattering coefficients are estimated from calculated BAW field [1]. Even though this technique is effective, its setup is too complicated...
ARFI displacements have been shown to share an inverse relationship with shear wave speed — based estimates of tissue elasticity. Both ARFI and shear wave elasticity imaging (SWEI) have been used to track the stiffening and softening of myocardium through the cardiac cycle in open-chest, intracardiac, and Langendorff preparations. In transthoracic imaging, induced shear waves have been observed during...
A general purpose finite element model that yielded directly the nonlinear frequency response of the second harmonic generation in SAW IDT resonators was developed. The model enabled us to study the effects of the nonlinear material constants, voltage drive, duty factor, and IDT geometry on f-2f nonlinear interactions. Specifically we have applied our model to the study of nonlinear frequency response...
Type I Lamb wave modes exhibit a strong affinity toward multimode behavior, especially the high-transduction-efficiency modes: S0 and S1 mode. Apodization, the standard technique to suppress the transverse modes for IDT-excited resonators, suffers from drawbacks such as additional loss and reduction of the effective coupling coefficient (k2eff). Most Lamb wave modes in AlN show a positive slope in...
I.H.P. SAW (Incredible High-Performance SAW) has a novel multi-layered structure to confine SAW energy in substrate surface area, and it shows extremely high quality (Q) factor, low temperature coefficient of frequency (TCF) and improved electromechanical coupling coefficient (K2). This paper introduces its mechanism of the high acoustic Q factor, both theoretically and experimentally, and its applications...
Spurious modes (SMs) result in in-band ripples and degrade the out-of-band rejection of filters, thus impeding the synthesis of high performance filters with MEMS resonators. Therefore, the ability to predict the presence of SMs in specific resonator geometries is highly desired and different techniques have been explored such as: 1-D/2-D analytic models, and 2-D/3-D finite element methods (FEM)....
Finite element method (FEM) has been extensively used for analyzing both static and dynamic behaviour of CMUTs. Typical parameters being evaluated include the pull-in voltage, pressure, sensitivity, bandwidth, and crosstalk. PZFlex is a commercial FEA software and has been optimized for the ultrasound industry and is commonly used to design piezo-electric ultrasound transducers. However, PZFlex is...
The growing complexity in RF front-ends, which support carrier aggregation and a growing number of frequency bands, leads to tightened nonlinearity requirements in all sub-components. The generation of third order intermodulation products (IMD3) are typical problems caused by the non-linearity of SAW devices. In the present work, we investigate temperature compensating (TC) SAW devices on Lithium...
One of the major cause for the attenuation of ultrasonic waves in polycrystalline materials is the random scattering at the grain boundaries — grain boundary scattering (GBS) —, whereby the acoustic mismatch is the result of the random orientation of the mechanical properties of the single crystals within the individual grains. Various analytical models, such as the unified theory, have been developed...
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