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Aluminum nitride (AlN) Lamb wave resonators (LWRs) utilizing the lowest symmetric (S0) mode have attracted much interests since they have high frequencies, low motional impedances, and capability of multiple frequencies on a single chip. However, the transverse spurious modes are often strong in AlN LWR, and largely degrade the performance in application, so suppression the transverse mode is highly...
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...
This paper presents the characterization of frequency response and mode shape at the 1st harmonic frequency of a Micro-Opto-Mechanical Acoustic Sensors (MOMAS) with a Mach-Zehnder Interferometer (MZI) readout system. In previous research, the static modeling and characterization has been demonstrated. In this paper, we investigate the capability of using MOMAS in ultrasound domain as a Micro-Opto-Mechanical...
One of the primary motivations for using ultrasound reflectometry for fingerprint imaging is the promise of increased spoof resistance over conventional optical or capacitive sensing approaches due to the ability for ultrasound to determine the elastic impedance of the imaged material. A fake 3D printed plastic finger can therefore be easily distinguished from a real finger. However, ultrasonic sensors...
Piezoelectric ultrasonic motors (PUMs) are based on the concept of driving the runner by a mechanical vibration excited on the stator via the converse piezoelectric effect. They exhibit merits of small size, simple structure, quick response, high accuracy and resolution, self-locking when power off and a lack of electromagnetic radiation. The linear PUMs become the research focus in recent years as...
Intravascular ultrasound (IVUS) is a well-established diagnostic method that has been applied frequently for providing high-resolution images of vessel wall and atherosclerotic plaques. Side looking transducer has been employed in a catheter for delineating the structure of vessel wall and lesions. However, it is difficult to get the flow distribution in the vessel by side looking transducer as the...
Coupling between surface acoustic waves (SAW) and arrays of mechanical resonators has appeared early in SAW history as a potential means to slow down wave propagation through mass-loading, in particular by creating corrugations on the substrate surface. This concept has been revisited over the past few years in the context of locally-resonant phononic crystals where pillars deposited on a homogeneous...
Conventionally, images are normally displayed by amplitude or intensity information. However, the frequency information is significantly important in acoustic images since the frequency information can reflect the object characteristics (surface profiles, structures hidden under surfaces, and material properties of objects). In this study, we propose a method of displaying frequency information in...
A U-shaped linear piezoelectric ultrasonic motor (PUM) was proposed, designed and tested in this work, in which three longitudinal transducers were used together to achieve the linear driving by two feet synchronously. Longitudinal vibrations of the transducers were generated with certain temporal shift to form the desired elliptical movements on the two driving feet. Finite element method (FEM) was...
This paper describes the design, fabrication, characterization and test of three sectorized array transducers: one for air-coupled operation (400 kHz, 25 mm diameter) and two for water-coupled operation (4 MHz, 10 mm diameter and 2 MHz, 5 mm diameter). The objective is to use these transducers in pulse-echo mode along with a conical reflector to generate a 2D cylindrical acoustic field with angular...
Hydraulic actuators has been utilized for various types of robots. However, hydraulic control system for multiple degrees of freedom mechanisms has a large volume because such system needs many control components. The purpose of this research is to develop a small hydraulic flow control valve. In the previous research, we have developed a small flow control valve using particle excitation by a piezoelectric...
Large and small CMUT membranes were fabricated in an interlaced fashion to create a multi-frequency array using a modified standard silicon-nitride sacrificial release process on a scale smaller than the wavelength to ensure the minimization of grating lobes. A 7 mm by 7 mm multi-frequency array with 20 elements was fabricated and wire-bonded to custom printed circuit boards (PCBs) mounted onto a...
It is generally difficult to adopt label-free biosensors, such as quartz-crystal-microbalance (QCM) biosensor and surface-plasmon-resonance biosensor, for diagnosis, because analyte contains many impurity proteins, whose concentrations are much higher than the target protein; they adsorb the sensor surface nonspecifically, obscuring the minute response caused by the targetprotein adsorption. Therefore,...
Temperature stability is critical for commercial oscillators and many methods have been explored such as: a) constant-resistance-based control methods; b) DTCMs with look-up tables; c) phase-lock-loop based control methods. Whereas exemplary results have been attained with these techniques, to be effective they require: a) accurate knowledge of the source of temperature fluctuations; (b) the use of...
Film bulk acoustic wave resonator (FBAR) filters are promising for the mobile communication devices. Frequency switchable filters are suitable for selecting the vacant frequency bands. Usual polarity unidirectional single layer resonator excites fundamental mode whereas polarity inverted double layer resonator excites second mode. In this study, we considered that polarity inverted structure is easily...
Functional Ultrasound (fUS) has shown to be a promising new neuroimaging modality that uses ultrafast plane waves to detect changes in cerebral blood flow for imaging brain activity at high spatiotemporal resolution. An existing challenge is the ultrasound penetration of skull which decreases with frequency. In the initial study (Macé et al., 2011)[1] a craniotomy was required to perform fUS. Since...
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...
We explore the frequency dependence of piezoceramic disc transducers bonded to plates. For some transducer dimensions, the frequency response shows a sharp peak. This behavior is inconsistent with the use of short pulses or broadband chirps for flaw localization. We use finite element simulation to show that the highly resonant behavior is caused by a high-strain region immediately beneath the transducer...
Transmit filters comprising piezoelectric resonators are fabricated in a Thin Film Bulk Acoustic Resonator (FBAR) technology. A filter's 2nd harmonic emissions (H2), generated by the resonators in the filter's output stage must be sufficiently small to prevent the filter from desensitizing a nearby receiver. Anti-parallel and anti-series connected resonator configurations, in which the H2 emissions...
Resonator based S0 Lamb wave mode in AlN thin films plate has drawn great attentions thanks to its high phase velocity up to 10 km/s and large electromechanical coupling coefficient (K2). Moreover, this structure allows operation at high temperature conditions. Although several significant research efforts are ongoing to enable AlN-based piezoelectric devices for high temperature applications, an...
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