Transducer Performance Research Articles

The Imaging Performance of Diagnostic Ultrasound Scanners Using the Edinburgh Pipe Phantom to Measure the Resolution Integral - 15Years of Experience.

The grayscale imaging performance of a total of 368 different scanner/transducer combinations from 39 scanner manufacturers measured over a period of 15 years is presented. Performance was measured using the resolution integral, a single figure-of-merit to quantify ultrasound imaging performance. The resolution integral was measured using the Edinburgh Pipe Phantom. Transducers included single element, linear, phased, curvilinear and multi-row arrays. Our results demonstrate that the resolution integral clearly differentiates between transducers with varying levels of performance. Two further parameters were also derived from the resolution integral: characteristic resolution and depth of field. We demonstrate that these two parameters can successfully characterize individual transducer performance and differentiate between transducers designed for different clinical and preclinical applications. In conclusion, the resolution integral is an effective metric to quantify and monitor grayscale imaging performance in clinical practice.

From Anatomy to Functional and Molecular Biomarker Imaging and Therapy: Ultrasound Is Safe, Ultrafast, Portable, and Inexpensive.

Ultrasound is the most widely used medical imaging modality worldwide. It is abundant, extremely safe, portable, and inexpensive. In this review, we consider some of the current development trends for ultrasound imaging, which build upon its current strength and the popularity it experiences among medical imaging professional users.Ultrasound has rapidly expanded beyond traditional radiology departments and cardiology practices. Computing power and data processing capabilities of commonly available electronics put ultrasound systems in a lab coat pocket or on a user's mobile phone. Taking advantage of new contributions and discoveries in ultrasound physics, signal processing algorithms, and electronics, the performance of ultrasound systems and transducers have progressed in terms of them becoming smaller, with higher imaging performance, and having lower cost. Ultrasound operates in real time, now at ultrafast speeds; kilohertz frame rates are already achieved by many systems.Ultrasound has progressed beyond anatomical imaging and monitoring blood flow in large vessels. With clinical approval of ultrasound contrast agents (gas-filled microbubbles) that are administered in the bloodstream, tissue perfusion studies are now routine. Through the use of modern ultrasound pulse sequences, individual microbubbles, with subpicogram mass, can be detected and observed in real time, many centimeters deep in the body. Ultrasound imaging has broken the wavelength barrier; by tracking positions of microbubbles within the vasculature, superresolution imaging has been made possible. Ultrasound can now trace the smallest vessels and capillaries, and obtain blood velocity data in those vessels.Molecular ultrasound imaging has now moved closer to clinic; the use of microbubbles with a specific affinity to endothelial biomarkers allows selective accumulation and retention of ultrasound contrast in the areas of ischemic injury, inflammation, or neoangiogenesis. This will aid in noninvasive molecular imaging and may provide additional help with real-time guidance of biopsy, surgery, and ablation procedures.The ultrasound field can be tightly focused inside the body, many centimeters deep, with millimeter precision, and ablate lesions by energy deposition, with thermal or mechanical bioeffects. Some of such treatments are already in clinical use, with more indications progressing through the clinical trial stage. In conjunction with intravascular microbubbles, focused ultrasound can be used for tissue-specific drug delivery; localized triggered release of sequestered drugs from particles in the bloodstream may take time to get to clinic. A combination of intravascular microbubbles with circulating drug and low-power ultrasound allows transient opening of vascular endothelial barriers, including blood-brain barrier; this approach has reached clinical trial stage. Therefore, the drugs that normally would not be getting to the target tissue in the brain will now have an opportunity to produce therapeutic efficacy.Overall, medical ultrasound is developing at a brisk rate, even in an environment where other imaging modalities are also advancing rapidly and may be considered more lucrative. With all the current advances that we discuss, and many more to come, ultrasound may help solve many problems that modern medicine is facing.

Effect of Terfenol-D rod structure on vibration performance of giant magnetostrictive ultrasonic transducer

In this study, a giant magnetostrictive ultrasonic transducer was designed with Terfenol-D as the active material. The influence of different Terfenol-D rod structures on the performance of the giant magnetostrictive transducer was investigated. Finite element analysis was used to analyze the dynamics of the theoretical giant magnetostrictive transducer and to validate the design. Eddy current losses were simulated for Terfenol-D rods of various structures using finite element analysis in ANSYS Maxwell. Two different Terfenol-D rods were then fabricated with either slices along the axial direction or slit along the radial direction, then the impedance and amplitude of the magnetostrictive ultrasonic transducer composed of the two Terfenol-D rods were measured. The results suggest that sliced Terfenol-D rods can suppress eddy currents more effectively, resulting in higher energy conversion efficiency; therefore, the Terfenol-D rods of small giant magnetostrictive transducers should be sliced along the axial direction to suppress eddy currents, whereas radial slits should be adopted for the rods of large giant magnetostrictive transducers to ensure integrity of the Terfenol-D rod and avoid adverse effects on the vibration performance of the giant magnetostrictive transducer that are caused by cutting the rods.

Numerical study of the effect of core geometry on the performance of a magnetostrictive transducer

Intensive ultrasonic waves can be generated based on the magnetostriction effect. These waves are used in many industries such as engineering, agriculture, and food industry. In this study, nickel as a naturally abundant magnetostrictive material was used in the core of a magnetostrictive transducer. This study aimed to investigate the influence of core geometry on the behavioral performance of the magnetostrictive ultrasonic transducer. The results showed that slightly stretching (elongating) the cross-section of the core increases the maximum radial and longitudinal magnetostrictive forces. Moreover, in tapered cores, by increasing the cone angle up to 30°, the maximum radial magnetostrictive force increased and then decreased. By increasing the cone angle, the maximum longitudinal magnetostrictive force and the coil required voltage almost linearly decreased. A proper ultrasonic transducer should have maximum sound pressure variations in the medium (sample). Thus, the variations of the magnetostrictive force in the longitudinal direction (Z axis) should be maximized. The results indicated that the conical core with a cone angle of 30° has the highest variations of magnetostrictive force in the Z-direction.

Stability of an anisotropic dielectric elastomer plate

A variety of methods have been proposed to improve the performance of dielectric elastomer transducers, which lead to the anisotropic electromechanical behavior of the material. This paper theoretically analyzes the effect of material anisotropy on the diffuse modes of instability in dielectric elastomer plates. As a first step, a transversely isotropic material is considered in the present study. The linearized incremental theory is used and the plate thickness is considered in the stability analysis. The bifurcation equations are solved with Wolfram Mathematica (Wolfram Research, Inc., 2019) [1] to obtain the critical stretches under different electric field. It is found that, compared to the isotropic material, material anisotropy results in larger unstable regions and higher critical stretches above which the plate is stable. It is also shown that material anisotropy has a stronger influence on a thinner plate. As the plate thickness increases, the influence decreases.

Figures of merit for quantum transducers

Recent technical advances have sparked renewed interest in physical systems that couple simultaneously to different parts of the electromagnetic spectrum, thus enabling transduction of signals between vastly different frequencies at the level of single quanta. Such hybrid systems have demonstrated frequency conversion of classical signals and have the potential of enabling quantum state transfer, e.g., between superconducting circuits and traveling optical signals. This article describes a simple approach for the theoretical characterization of the performance of quantum transducers. Given that, in practice, one cannot attain ideal one-to-one quantum conversion, we explore how imperfections impact the performance of the transducer in various scenarios. We quantify how knowledge of the well-established transducer parameters signal transfer efficiency η and added noise N suffices to assess its performance in a variety of transduction schemes ranging from classical signal detection to applications for quantum information processing.

Development of wideband orthomode transducers for FAST cryogenic receiver system

This paper describes the design, construction, and performance of the wideband orthomode transducers (OMTs) for the L- (1.2–1.8 GHz), the S- (2–3 GHz) and the P- (0.56–1.12 GHz) band receiver systems of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These OMTs operate at the cryogenic temperature of 70K to reduce their thermal noise contribution to the receiver chains. The development on the FAST L- and S-band quad-ridged waveguide (QRWG) OMTs is carried out based on the theoretical mode analysis. In view of the miniaturization of FAST cryogenic receiver system at P-band, a novel wideband compact bowtie dipole OMT is designed with an octave bandwidth as well as a length of only quarter wavelength. The proposed L-, S- and P-band OMTs are designed and optimized by using Ansys High Frequency Structure Simulator (HFSS), and then manufactured, tested at room temperature. Measurement of FAST cryogenic receiver system noise is also performed with the L-, S- and P-band OMTs installed. The measured results fully comply with the design specifications.

Integration of Fe3O4 with Bi2S3 for Multi-Modality Tumor Theranostics.

The combination of reactive oxygen species (ROS)-induced chemodynamic therapy (CDT) and photothermal therapy (PTT) holds a promising application prospect for their superb anticancer efficiency. Herein, we created a novel Fe3O4@polydopamine (PDA)@bovine serum albumin (BSA)-Bi2S3 composite as a theranostic agent, by chemically linking the Fe3O4@PDA with BSA-Bi2S3 via the amidation between the carboxyl groups of BSA and the amino groups of PDA. In this formulation, the Fe3O4 NPs could not only work as a mimetic peroxidase to trigger Fenton reactions of the innate H2O2 in the tumor and generate highly cytotoxic hydroxyl radicals (•OH) to induce tumor apoptosis but also serve as the magnetic resonance imaging (MRI) contrast agent to afford the precise cancer diagnosis. Meanwhile, the PDA could prevent the oxidization of Fe3O4, thus supporting the long-term Fenton reactions and the tumor apoptosis in the tumor. The Bi2S3 component exhibits excellent photothermal transducing performance and computed tomography (CT) imaging capacity. In addition, the PDA and Bi2S3 endow the Fe3O4@PDA@BSA-Bi2S3 composite with an excellent photothermal transforming ability whichcould lead to tumor hyperthermia. All of these merits play the synergism with the tumor microenvironment and qualify the Fe3O4@PDA@BSA-Bi2S3 NPs for a competent agent in the MRI/CT-monitored enhanced PTT/CDT synergistic therapy. Findings in this research will evoke new interests in future cancer therapeutic strategies based on biocompatible nanomaterials.

Optimization and characterization of a wideband multimode Tonpilz transducer for underwater acoustical arrays

A multimode underwater acoustical transducer is well-known for providing wider bandwidth than a conventional single-mode transducer. However, the design of a low-frequency multimode transducer to achieve the desired wideband characteristics for an underwater array is challenging when considering the array’s size and weight limitations. Therefore, this study focused on the development of a multimode transducer structure for superior wideband characteristics. The effect of various structural parameters on the performance of the multimode Tonpilz transducer was first analyzed with emphasis on its bandwidth using the finite element method (FEM). Then, the structure of the transducer was improved by analyzing the effect of the side acoustic window and incorporating realistic design considerations. Finally, the improved transducer structure was optimized to have the widest possible bandwidth while maintaining its transmitting voltage response (TVR) level over a typical power requirement. The final design was validated by fabricating a prototype transducer and evaluating its acoustical performance.

Long-distance structural health monitoring of buried pipes using pitch-catch T(0,1) wave piezoelectric ring array transducers

In modern industries, long-distance guided wave inspection has been routinely used for various types of pipelines. The usage of T(0,1) wave is always of great interests since it is the only non-dispersive wave mode in pipes. In this work, a pair of pitch-catch piezoelectric ring arrays were proposed for long-distance structural health monitoring (SHM) of buried pipes. Firstly, the working principle of the proposed transducer was introduced. Next, the performances of thickness-shear (d15) and face-shear (d24) modes based piezoelectric ring transducers in T(0,1) wave generation and reception were comparatively tested. It was found that at most frequencies, it is best to employ the d15 ring as the exciter and the d24 ring as the receiver. Then, the signal-to-noise ratio (SNR) of the generated T(0,1) wave and its attenuation in pipes with different coating conditions were investigated to estimate the detectable distance using the proposed transducer. Results showed that after applying acoustical isolation layer on pipes, the proposed ring transducers can inspect buried pipes over 20 m. Finally, the performance of the ring transducers in defect detection was validated. This work is expected to provide a promising solution to long-distance SHM of buried pipes.

Three-Year Follow-Up with the Bone Conduction Implant

Background: The bone conduction implant (BCI) is an active transcutaneous bone conduction device where the transducer has direct contact to the bone, and the skin is intact. Sixteen patients have been implanted with the BCI with a planned follow-up of 5 years. This study reports on hearing, quality of life, and objective measures up to 36 months of follow-up in 10 patients. Method: Repeated measures were performed at fitting and after 1, 3, 6, 12, and 36 months including sound field warble tone thresholds, speech recognition thresholds in quiet, speech recognition score in noise, and speech-to-noise thresholds for 50% correct words with adaptive noise. Three quality of life questionnaires were used to capture the benefit from the intervention, appreciation from different listening situations, and the ability to interact with other people when using the BCI. The results were compared to the unaided situation and a Ponto Pro Power on a soft band. The implant functionality was measured by nasal sound pressure, and the retention force from the audio processor against the skin was measured using a specially designed audio processor and a force gauge. Results: Audiometry and quality of life questionnaires using the BCI or the Ponto Pro Power on a soft band were significantly improved compared to the unaided situation and the results were statistically supported. There was generally no significant difference between the two devices. The nasal sound pressure remained stable over the study period and the force on the skin from the audio processor was 0.71 ± 0.22 N (mean ± 1 SD). Conclusion: The BCI improves the hearing ability for tones and speech perception in quiet and in noise for the indicated patients. The results are stable over a 3-year period, and the patients subjectively report a beneficial experience from using the BCI. The transducer performance and contact to the bone is unchanged over time, and the skin area under the audio processor remains without complications during the 3-year follow-up.

Fabrication and performance of Tile transducers for piezoelectric energy harvesting

In recent years, pavement piezoelectric energy harvesting has become one of the most promising road energy harvesting system clean energy sources. However, it is difficult for existing piezoelectric transducer structures to meet road power generation requirements. In this study, ceramic grinding and polishing techniques were used to make curved piezoelectric ceramic units with controllable curvatures. A new type of Tile transducer for roadway applications was developed in combination with an elastic metal base. Under the action of traffic load, the Tile transducer was subject to both vertical stress and a horizontal tearing force. Laboratory tests were performed on Tile transducers with simply supported and fixed boundary conditions, and the effects of concentrated and uniformly distributed loads on energy harvesting efficiency were analyzed. When the excitation frequency was 6 Hz and the load was 0.7 MPa, the output power of the Plane transducer was 0.23 mW, while that of the Tile transducer was 24.5 times as large at 5.65 mW. The ultimate compressive yield strength of a single Tile transducer could reach 2.18 kN, and the load limit was 1.5 kN at an excitation frequency of 10 Hz. This meets traffic load requirements. The open circuit voltage peak did not decrease substantially when 360 000 cyclic loading processes were performed. This indicated that Tile transducer structural performance was stable and that the transducer was durable. Based on the test results, an effective Tile transducer packaging method is proposed for application in road power generation systems.

From nuclear physics to applications: detectors for beam handling, medical diagnostics and radioactive waste monitoring

Nuclear physics experiments are always in need of more and more advanced detection systems. During the last years relevant technological developments have come out with many improvements in terms of performance and compactness of detector materials, transducers, electronics, computing and data transmission. In light of these achievements some applications previously prohibitive, mainly because of size and cost, have become feasible. A few applications of nuclear detection techniques are discussed, starting from the neighboring field of particle beam diagnostics, moving to the medical diagnostics and ending up into the radioactive waste handling. New radiation sensors are shown and explained, as exploited in the DMNR project for the radioactive waste online monitoring which merged into the MICADO Euratom project.

Analysis of size dependency on Love-type wave propagation in a functionally graded piezoelectric smart material

This study investigates Love-type wave propagation in a layered structure consisting of a functionally graded piezoelectric material (FGPEM) stratum followed by a semi-infinite couple-stress substrate exhibiting microstructural properties. Dispersion relations are obtained for electrically open and short conditions. Possible particular cases are discussed. The dispersion relation is reduced to the classical Love wave equation to validate the results. The influence of microstructural parameters, electromechanical coupling factor, thickness, functional gradedness and material parameters of the FGPEM stratum on the phase velocity of the Love-type wave has been scrutinized and illustrated graphically for electrically open and short conditions. The findings have meaningful practical application in the enhancement of efficiency and performance of sensors and transducers.

Design and simulation of a flat cap mushroom shape microelectromechanical systems piezoelectric transducer with the application as hydrophone

A microelectromechanical systems piezoelectric transducer capable of measuring static accelerations and acoustic vibrations has been designed and proposed. The transducer is composed of a circular plate on a pillar, which is fixed at the centre and free at the rim so that it resembles a flat cap mushroom. An annular piezoelectric layer has been employed to convert the vibration-induced stress of the plate to a potential difference. The proposed structure has been compared with diaphragm piezoelectric transducers and hydrophones and its superior performance has been verified. Analytical models for both static and dynamic accelerations have been developed, discussed and the output voltage has been formulated, which is in a very good agreement with the finite element analysis. Results show that the maximum sensitivity is achieved when there is an annular piezoelectric layer on the plate around the pillar perimeter. The effect of different geometrical parameters on the transducer performance has been studied. The proposed flat cap mushroom shape piezoelectric transducer could achieve −186.5 dB sensitivity and a very wide bandwidth. Another important advantage of the proposed structure is that by controlling the pillar radius and without changing the plate size, the sensitivity can be enhanced.

Ultrasonic Transceiver with a Regular/Periodic 1-3 Piezocomposite Based on the SAW Resonance Mode on Damping Backing

A novel effective vibrational mode was discovered in the conventional transducer with an array of orthogonal (square) regular piezoelectric rods in 1-3 piezocomposite, containing the damping backing and front matching layers. The operational resonance in the structure was determined as the Surface Acoustic Wave (SAW) on the backing boundary excited by the adjacent piezo-rods, with its frequency typically near 3 times lower the fundamental half-lambda conventional piezocomposite resonance. Pulse-echo sensitivity and transmitting sound pressure level (SPL) in air showed that the signal strength is roughly comparable to the industrial similar air transducers at the frequency range 100–700 kHz, where at these frequencies the lateral and longitudinal piezoelement dimensions in the conventional transducer design are typically close to each other causing interference with unwanted coupling modes. As was determined theoretically and proved in experiments, the backing SAW resonance effect in the transducer performance is inherent just to the regular periodic 1-3 piezocomposite structure and does occur neither with randomly located/oriented piezo-rods nor in the homogeneous piezo-plate at least with the same lateral cross-section as the connected to it backing. The purpose of the article is to investigate a newly discovered operational vibrational mode of a SAW type in 1-3 regular piezocomposite, other than piezoelectric resonance. The investigated phenomena can improve the transceiver sensitivity and bandwidth, providing lower drive voltage and smaller and lighter weight ultrasonic transducers. Based on the piezocomposites with thickness’ 1–1.5 mm (rod resonance near 2–3 MHz), pillar width 0.2–0.8 mm, kerf width 0.1–0.4 mm, the transceivers with an operating frequency from 140 kHz to 650 kHz were designed and fabricated with a conventional backing of a mixture of high-density tungsten powder and epoxy and a matching layer of a mixture of low-density glass bubbles and epoxy. Experimental evaluation of their acoustical performance showed expected characteristics suitable for practical applications.

An optimization design strategy of 1–3 piezocomposite ultrasonic transducer for imaging applications

An optimization design strategy based on finite element method (FEM) and particle swarm optimization (PSO) algorithm is developed to fabricate high-performance 1–3 piezocomposite ultrasonic transducer. In this strategy, the structure and performance of ultrasonic transducer are simulated by FEM based PZFlex software to analyze the effect of design parameters (ceramic volume fraction and kerf width) on its performance. Due to the time-consuming of FEM simulation, based on the data obtained by simulations, artificial neural network models are established to describe the mapping relation of the design parameters and performance parameters (center frequency and high electromechanical coupling coefficient). The multi-objective optimization criterion is constructed for ultrasonic transducer, and then the modified PSO algorithm are adopted to optimize design parameters. According to the optimized design parameters, the FEM simulation and experiment are conducted to validate the effectiveness of the developed strategy. The simulation and experiment results are in agreement with the designed performance, which indicates that the developed strategy can be used to optimize design parameters for fabricating high-performance ultrasonic transducer. In addition, the imaging experiments of tungsten wires and RMB coin prove the high imaging performance of the ultrasonic transducer fabricated by the developed strategy.

Improving transducers for rotational energy harvesting

Researchers exploit the static instability of the centrifugal softening effect to increase power performance of piezoelectric transducers for rotational energy harvesting.

Electrical conduction in dielectric elastomer transducers

Dielectric elastomers are considered to be promising materials for applications in energy harvesting, haptic interface or biomedical actuation, thanks to their high energy density and attractive efficiency. Nevertheless, the performance of dielectric elastomer transducers (DETs) are affected by losses, especially losses induced by leakage current. This work reports an extensive investigation into the stability of the current-time characteristics of VHB4910 dielectric elastomers, currently in use for such applications. It should be noted that conductive pastes that act as compliant electrodes play an important role in the behavior of the current. The Schottky current is thus disturbed at the electrode — elastomer interface and an increase in current is observed over time when the device is subjected to electrical voltages over long periods of time. Pre-stress, commonly applied for application using VHB4910, influences also significantly the electrical response. Thus, for a same stretching of the material, asymmetric stretching is preferred over symmetric stretching in order to obtain a lower leakage current. This difference in behavior is explained by the fact that the polymer chains are stretched in preferential directions which will then lead to specific responses of both the dipoles and other conduction mechanisms such as hopping. Finally, a simple analytical model is proposed to report the current behavior in these materials according to the nature of the electrodes and the pre-stretching applied.

Microwave-to-optical transduction using a mechanical supermode for coupling piezoelectric and optomechanical resonators.

The successes of superconducting quantum circuits at local manipulation of quantum information and photonics technology at long-distance transmission of the same have spurred interest in the development of quantum transducers for efficient, low-noise, and bidirectional frequency conversion of photons between the microwave and optical domains. We propose to realize such functionality through the coupling of electrical, piezoelectric, and optomechanical resonators. The coupling of the mechanical subsystems enables formation of a resonant mechanical supermode that provides a mechanically-mediated, efficient single interface to both the microwave and optical domains. The conversion process is analyzed by applying an equivalent circuit model that relates device-level parameters to overall figures of merit for conversion efficiency η and added noise N. These can be further enhanced by proper impedance matching of the transducer to an input microwave transmission line. The performance of potential transducers is assessed through finite-element simulations, with a focus on geometries in GaAs, followed by considerations of the AlN, LiNbO3, and AlN-on-Si platforms. We present strategies for maximizing η and minimizing N, and find that simultaneously achieving η > 50 % and N < 0.5 should be possible with current technology. We find that the use of a mechanical supermode for mediating transduction is a key enabler for high-efficiency operation, particularly when paired with an appropriate microwave impedance matching network. Our comprehensive analysis of the full transduction chain enables us to outline a development path for the realization of high-performance quantum transducers that will constitute a valuable resource for quantum information science.