Current Issue : January-March Volume : 2025 Issue Number : 1 Articles : 5 Articles
Recent publications on acoustic MEMS transducers present a new three-dimensional folded diaphragm that utilizes buried in-plane vibrating structures to increase the active area from a small chip volume. Characterization of the mechanical properties plays a key role in the development of new MEMS transducers, whereby established measurement methods are usually tailored to structures close to the sample surface. In order to access the lateral vibrations, extensive and destructive sample preparation is required. This work presents a new passive measurement technique that combines acoustic transmission measurements and lumped-element modelling. For diaphragms of different lengths, compliances between 0.08 × 10−15 and 1.04 × 10−15 m3/Pa are determined without using destructive or complex preparations. In particular, for lengths above 1000 μm, the results differ from numerical simulations by only 4% or less....
This paper presents the introduction, design, and experimental validation of two small helical antennae. These antennae are a component of the surface acoustic wave (SAW) sensor interrogation system, which has been miniaturized to operate at 915 MHz and aims to improve the performance of wireless passive SAWtemperature-sensing applications. The proposed antenna designs are the normal-mode cylindrical helical antenna (CHA) and the hemispherical helical antenna (HSHA); both designed structures are developed for the ISM band, which ranges from 902 MHz to 928 MHz. The antennae exhibit resonance at 915 MHz with an operational bandwidth of 30 MHz for the CHA and 22 MHz for the HSHA. A notch occurs in the operating band, caused by the characteristics of the SAWsensor. The presence of this notch is crucial for the temperature measurement by aiding in calculating the frequency shifting of that notch. The decrement in the resonance frequency of the SAW sensor is about 66.67 kHz for every 10 ◦C, which is obtained by conducting the temperature measurement of the system model across temperature environments ranging from 30 ◦C to 90 ◦C to validate the variation in system performance....
This study proposes a single-stage lattice-type acoustic filter using an analytical solution method for either a narrow passband filter or a wider passband filter using two kinds of parameter assignments in the Butterworth–Van Dyke (BVD) model. To achieve the goal of a large bandwidth or high return loss, two first-order all-pass conditions are used. For multi-stage lattice-type filters, the cost function is defined and design parameters are extracted by using pattern search, while the initial values are provided through single-stage design to shorten optimization time and allow convergence to a better solution. This method provides the S-parameter frequency response for the filter on the YX 42◦ cut angle of lithium tantalate (electromechanical coupling coefficient of about 6%) that can meet the system specifications as much as possible. Finally, the three-stage lattice-type was applied to various 5G bands with a fractional bandwidth of 2–5%, resulting in a passband return loss of 10 dB and an out-of-band rejection of 40 dB or more....
Microplastics have emerged as ubiquitous contaminants, attracting increasing global attention. Recent evidence confirms the presence of microplastics in human blood, suggesting their potential to interact with cells and induce adverse physiological reactions in various organs as blood circulates. To quantify the distribution of microplastics and assess their potential effects on human health, the effective separation of microplastics from blood is crucial. However, current methods for separating microplastics from blood are limited in effectiveness and simplicity. This study proposes a microfluidic device that utilizes traveling surface acoustic waves to separate microplastics from blood. While traveling surface acoustic waves have been employed to separate various particles, a systematic study on the separation of microplastics from blood samples has not been previously reported. Specifically, the theoretical values of the acoustic radiation factor for various types of microplastics and blood cells were investigated. The significant differences in resonant frequencies indicated the feasibility of separating microplastics of different sizes and types from blood cells. Experimental validation was performed using a polydimethylsiloxane microfluidic device on a piezoelectric lithium niobate substrate. The device successfully separated 5- and 10-micrometer polystyrene microplastics from blood samples. The effects of power and flow rate on separation efficiency were also systematically investigated. This study provides a novel approach for the effective separation of microplastics from blood, contributing to the assessment of their distribution and potential health impacts....
Collichthys lucidus is an important small-scale economic fish species in the Yangtze River Estuary. To improve the accuracy of acoustic stock assessments for C. lucidus, it is necessary to accurately measure its target strength (TS). This study obtained precise morphological parameters of C. lucidus through X-ray scanning and established a Kirchhoff ray mode (KRM) model to simulate the changes in TS of the fish body and swimbladder at different acoustic frequencies and pitch angles. At the same time, the TS was measured using the tethered method to analyze and compare the broadband scattering characteristics obtained from both methods. An empirical formula of C. lucidus relating TS to body length at two conventional frequencies was established using the least squares method. The results show that the C. lucidus TS changes, with body length ranging from 10.91 to 16.61 cm, are significantly influenced by the pitch angle at 70 kHz and 200 kHz frequencies, and the fluctuation of TS for both the fish body and swimbladder increases with the rise in frequency. The broadband TS values estimated by the KRM model and measured by the tethered method fluctuate within in the ranges from −45 dB to −55 dB and −40 dB to −55 dB, respectively. The TS of C. lucidus tends to increase with the increase in swimbladder length. When the probability density function of the pitch angle is N(−5◦, 15◦), the b20 measured by the KRM and the tethered method at 70 kHz are −71.94 dB and −69.21 dB, respectively, while at 200 kHz they are −72.58 dB and −70.55 dB. This study provides a scientific basis for future acoustic target discrimination and stock assessment of C. lucidus in the Yangtze River Estuary....
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