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This paper presents an equivalent circuit model of a piezoelectric micromachined ultrasonic transducer (PMUT) array, combining an acoustic coupling model originally developed for capacitive micromachined ultrasonic transducer (CMUT) arrays and an electro-mechanical model of the individual PMUTs in the array. This model is experimentally validated with PMUT arrays of varied sizes and accurately predicts...
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...
A piezoelectric plate, poled along its thickness, that supports on its top surface a periodic grating of electrodes is considered. If wave propagation is assumed along the length of the plate, one demonstrates that an electrical Bragg band gap can be observed, depending on the electrical boundary conditions applied on the electrodes. This gap is associated with a discontinuity of the electric field...
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...
The matching layer inserted between the front protection metal and piezoelectric layer has been designed when the protection metal is half-wavelength thick. This matching layer plays the role of a bonding layer. The optimum thickness ranges from λ/4 to 3λ/8 in the Mason model simulation, which has been confirmed by experiments. In the optimum range, the sensitivity was much higher and the bandwidth...
Ultrasounds are a proven medical tool to assess some biological processes, including breast cancer screening, fetal development and blood perfusion. However, ultrasounds also have the potential to deliver power and telemetry capabilities to deeply implant devices, surpassing some of the challenges faced by coils or antennas operating inside the human body. In this paper, we present a small-form implantable...
Electrical impedance characterization is often used to evaluate the electro-mechanical parameters of Capacitive Micromachined Ultrasonic Transducers (CMUTs). Evaluation is achieved by fitting the measured data with simple equivalent circuit models, which do not account for many parasitic phenomena. Such parasitic phenomena may include resistive and inductive behavior of electrical interconnections,...
Measurement of transducer impedance in ultrasound systems indicates both the performance of a transducer and the presence of damaged elements and cables. Load impedance analysis is typically performed with dedicated test equipment and is a time consuming and thus expensive process, especially for high channel count systems. This paper proposes a method for the measurement of channel source impedance...
To understand physiologic state in diseased liver e.g. non-alcoholic steatohepatitis, this study aims to analyze the acoustic impedance (Z) of hepatic cells using a scanning acoustic microscopy (SAM). Ultrasound scattering sources in cells, however, cause the multi-reflection and prevent from analyzing the precious value of Z although it provides the useful information of structure in cells (M. N...
Electrical impedance characterization represents a practical way to evaluate the electro-mechanical parameters of Capacitive Micromachined Ultrasonic Transducers (CMUTs). This paper describes an accurate CMUT characterization method able to evaluate the electro-mechanical and parasitic parameters by fitting electrical impedance measurements at several bias voltages with an improved equivalent circuit...
We numerically report a high efficient acoustic lens using a flat artificial composite plate in water, which is designed using silicone films deposited on PMMA plate engraved with the annular grooves. The focusing effect is due to the phase of the plate changing with the height of PMMA variation, while the total height of the plate is held constant. As both PMMA and silicone are low impedance mismatch...
In order to study relaxation characteristics of viscoelasticity of the liquid, a wide frequency sweep in the range of MHz to GHz is desired. We, therefore, report a new type HBAR (High overtone Bulk Acoustic Resonator) sensor which makes it possible to operate in a wide frequency range. We choose AT-cut quartz as the substrate whose TCF is zero at room temperature to suppress frequency shifts due...
SH-SAW In-liquid sensors have been explored extensively in recent decades. They propose an ability to work at higher frequencies, than the well-known QCM, with the aim to reduce the size and ease the integration in sensor arrays. So far SH-SAW liquid phase sensors are designed in two-port delay line configurations because of the need to protect the IDT from the conductive and dielectric loads from...
In previous work, the advantage of using super-harmonic contrast imaging to visualize the microvasculature in tumors and organs has been demonstrated [1]. This was performed using dual frequency (DF) probes consisting of a high frequency single element transducer from a motorized probe concentric with a low frequency ring [2]. However, mechanically scanned systems have limitations, including single...
Periodic calibration of ultrasound imaging and instrumentation systems is critical to identify transducer condition or system failure. Performing impedance measurement allows the monitoring of transducer degradation and cable failure, typically using a dedicated impedance analyzer. This paper proposes a method of concurrent in-situ impedance measurement of all array elements without instrumentation...
Ultrasound (US) brain stimulation has been demonstrated to be a promising approach for noninvasive neuromodulation. However, traditional methods always demand animals to be under anesthesia and body constraint to achieve stable operation with bulky US transducer, while those demands would result in interference to the neural activity related to perception, cognition, and behavior. Appling a miniature...
BaTiO3 ceramic doped with cobalt and calcium (BTCaCo), processed by a conventional technique with a reduced sintering temperature, is characterized. Particular attention is paid to the delivery of complete and accurate set of elastic, dielectric, and piezoelectric constants. These databases are relatively rare in the literature but are essential for numerical simulations of new devices, integrating...
This paper presents the development of focused single element ultrasound transducers for photoacoustics. Two transducer technologies using 36° rotated Y-cut LiNbO3 have been implemented and compared, namely a LiNbO3 crystal bonded to a glass lens and a shaped piezo-composite. The 50MHz transducer design with an acceptance angle greater than 60° has been optimized by analytical and finite element simulation...
Short pulse transmission and reception is important for piezoelectric micromachined ultrasonic transducer (PMUT) arrays to achieve high resolution. However, coupling effects cause PMUT arrays to exhibit long decay times following the transmit pulse and poor axial resolution. Here, we model the mutual acoustic impedance that couples PMUTs in an array to show that the decay behavior can be accurately...
The following study is focused on the CMUT intrinsic efficiency for therapeutic purposes. The simulation work is based on electromechanical equivalent circuit analysis and is verified thanks to impedance measurements and pressure field scanning. The good agreement between the overall experiences provides useful understanding on the CMUT behavior and optimization guidelines for therapy-specific CMUT...
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