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Liquids density measurements are highly required in both research and industrial applications, from process control in petrochemical industry to product monitoring in food processing. Commercial devices are often expensive or unwieldy; therefore, in a previous work, a cheap and handy resonant sensor, based on a piezoelectric bimorph, was introduced. The operating principle is based on the variation...
In this research, piezoelectric micromachined ultrasonic transducer (pMUT) array was used for stimulation of mechanosensitive channel of HEK293T cells. The fabricated pMUT array was made by microelectromechanical system (MEMS) technology such as photo process, etching, sputtering, and sol-gel method. The resonance frequency and acoustic positive peak pressure were 2.07 MHz and 3.94 kPa, respectively...
In this study, a torsional transducer type ultrasonic motor which realizes the continuous rotation and the positioning of the angle in cryogenic temperature has been fabricated and evaluated. In the cryogenic temperature environment, the performance of the transducer falls. In order to drive the motor at cryogenic temperature, the torsional transducer is designed to generate the resonant stick-slip...
Nonlinear generation of harmonics is measured at wafer level on Temperature Compensated Surface Acoustic Wave (TC-SAW) Resonators on lithium niobate. The obtained results are different from those published for resonators on lithium tantalate. For second harmonic, strong peaks looking like multiple resonant modes are found. The frequency difference between the successive peaks increases when the substrate...
The B/A parameter is a second order distortion ratio defined in nonlinear acoustics. Pulse echo method has been shown to be a suitable way for the parameter measurement using a simple experimental set-up. We show how to improve the sensitivity of the method without any change in the apparatus and modus operandi.
Capacitive Micromachined Ultrasonic Transducers (CMUTs) fabricated using Silicon-On-Insulator (SOI) wafers often have large thickness variation of the flexible plate, which causes variation in both pull-in voltage and resonant frequency across the CMUT array. This work presents a bond and boron etch-stop scheme for fabricating the flexible plate of a CMUT. The proposed fabrication method enables precise...
The key parameters for the design of a capacitive micromachined ultrasonic transducer (CMUT) cell are the dimensions of the vibrating plate, i.e. plate diameter and thickness, and the gap height. These dimensions together with the magnitude of the dc bias voltage determine the transducer's center frequency, bandwidth, and transmit and receive sensitivity. For a given center frequency, choosing the...
Acoustic beam diffraction phenomena for normal beam incidence to a viscoelastic plate, such as resonance frequency downshift, beam narrowing, and axial signal enhancement near certain leaky Lamb modes, have been demonstrated in recent years, as compared to plane-wave analyses. A close correlation between these phenomena and apparantly different guided-wave dispersion phenomena, including negative...
Capacitive micromachined ultrasonic transducers (CMUTs) make extremely sensitive chemical sensors in air. In this work, we demonstrate a CMUT chemical sensor chip with integrated temperature and pressure sensors. These sensors allow the measurement of multiple environmental parameters using a single chip and allow the influence of temperature and pressure on the chemical sensors to be corrected for...
Acoustic radiation force has many applications. One of the related technologies is the ability to noninvasively expel stones from the kidney. To optimize the procedure it is important to develop theoretical approaches that can provide rapid calculations of the radiation force depending in stone size and elastic properties, together with ultrasound beam diameter, intensity, and frequency. We hypothesize...
Low-loss Surface Acoustic Wave (SAW) resonator-type filters, such as double mode SAW filters (or Coupled Resonator Filters, DMS/CRF), can be considered as transformers. Such a RF SAW “transformer-filter” could operate directly on one of the ISM bands and be useful, for example, in “wake-up” radios, since the RF voltage can be raised by passive means prior to rectification. Here, we propose to use...
Phononic crystals (PnC) consist of two or more materials arranged in a spatially periodic manner. Introduction of a defect into the crystal lattice is a technique to create resonant modes. The idea behind the application of a PnC as sensor element is the dependence of the characteristic features of those modes on speed of sound. Currently the sensor designs are based on common 2D phononic crystal...
This paper discusses SAW-BAW-based band reject filters. They are composed of the impedance converters, where capacitive elements are replaced with SAW/BAW resonators. First, basic properties of the unit cell are studied. It is shown how basic properties of a unit cell change with the design. It is also shown that when two notches caused by the resonators are placed in proximity, two synergy effects...
This work is focused on the application of Phononic Crystals to reduce anchor losses of MEMS contour mode resonators. Anchor losses dominates the losses in these type of released resonators at low frequency and at low temperature. The use of phononic crystals, intended as finite-periodic distribution of holes in the anchor, is fully compatible with fabrication processes and moreover it is easy to...
The point of this publication is that on substrates with high electromechanical coupling metal elements (IDT, short-circuited gratings etc.) create very important sources of loss. By changing to open-circuited gratings (with corresponding change in gratings period) the achievable values of Q-factor (Q) reach several thousand at about 1 GHz in single port resonators. Etching grooves and removing metal...
This paper investigates the possibility of using ferroelectret films to produce wideband ultrasonic transducers for applications in water immersion and medical imaging. Ultrasonic transducers with different sizes (apertures) were fabricated using a polypropylene ferroelectret film (0.6 MHz thickness resonant frequency) as active component. Then, they were characterized in pulse-echo operation mode...
The experimental studies of temperature coefficient of frequency (TCF) of SAW resonators were usually modeled by TCF models first proposed by Bechmann, Ballato and Lukaszeck[1]. These models unfortunately were not frame invariant with regards to the material property tensors of the crystal substrate and metal interdigital transducers (IDTs). Furthermore the models did not have the 3rd order nonlinear...
This paper presents fabrication methods using graphene as a membrane that was thermally bonded on top of the CMUT cavity formed by patterned photoresist. The impedance measurement result showed graphene CMUT exhibit high resonance frequency when membrane size remains large. Previously we had also reported such a graphene CMUT with stiction problem caused by a graphene transfer technique. In the newly...
In this paper, we compare the zero reflection and the power maximization conditions to calculate the optimal electric load for maximum US energy absorption by receivers with the KLM model. In experiments with a 1–3 composite transducer, the predictions agree with the measurements at the resonance frequency. Results at the anti-resonance deviate slightly from predictions due to a parasitic load and...
Accurate diagnostics of stenosis and blood flow distribution in carotid arteries requires transducers capable of producing 3D volume images with high frame rate for real time imaging. In the process of designing a matrix probe, an important goal is to realize the acoustic stack with high sensitivity and bandwidth. In this study, we employ a finite element analysis to evaluate the effect of sub-dicing...
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