Ultrasonic Transducer Research Articles

The resonant behavior of airborne standing-wave acoustic levitators based on arrays of ultrasonic transducers

Recently airborne standing-wave acoustic levitation has seen great advances, and its applicability has been broadened due to the development of cavities constructed with arrays of compact ultrasonic sources. Yet, the numerical methods employed to study and predict the pressure distributions inside these cavities do not consider the effect of multiple reflections on the boundaries, hiding their resonant effects. This work presents an analytical, numerical, and experimental study of the effect of multiple reflections inside ultrasonic cavities based on arrays of transducers exhibiting their influence on the pressure amplitudes of focused standing waves. Our numerical results come from a modified version of the Matrix Method to numerically compute the multiple wave reflections of cavities constructed by two opposite arrays of multiple compact sources as boundaries. The correlation between numerical and experimental results reveals that intra-cavity reflections are relevant in focused axisymmetric cavities based on two arrays of multiple ultrasonic sources having a considerable impact on the amplitude of the standing waves and consequently, on the acoustic levitation performance. Thus, intra-cavity reflections must be considered for optimal cavity designs.

High Sensitivity Performance of Piezoelectric Micromachined Ultrasonic Transducer Employing Sc-Doped AlN Thin Film

Abstract Aluminum Nitride (AlN) based piezoelectric micromachined ultrasonic transducers (PMUTs) have been the prime choice in acoustic imaging, because it has advantages of high frequency and thus high resolution. However, low piezoelectric constants of AlN gives rises to limitation in transmitting sensitivity. Scandium (Sc) doping method for AlN can be used to improve its piezoelectricity. In this paper, single element PMUT based on ScAlN thin film was proposed and modeled by performing finite element method (FEM). Influence of different electrode configurations on PMUT performance were studied. The results show that, compared with other electrode configurations, PMUT has the best overall performance when the upper electrode is platinum (Pt) and the lower electrode is molybdenum (Mo). In addition, the acoustic field characteristics and its dynamic analysis of PMUT based on ScAlN in water were studied. The investigation results demonstrated that the relative pulse-echo sensitivity level M of PMUT is significantly improved with the increase of Sc doping concentration in AlN thin film. When the Sc concentration is 40%, the M reaches -44 dB, which is 20 dB higher than that without Sc (-64 dB). The PMUT based on the high Sc-doped AlN thin film has a larger effective electromechanical coupling coefficient and sensitivity, which is beneficial to the application in high sensitivity ultrasound imaging.

An integrated dual-frequency IVUS system with interleaved sampling and parallel signal processing based on FPGA

Abstract Due to the lack of high voltage and low frequency pulse transmission channels, commercial high frequency IVUS imaging system cannot meet the hardware requirements of ultrasound angiography. Therefore, it is of great research significance to develop a dual-frequency IVUS rotary imaging system with high integration, high sampling rate and sampling accuracy. In this work, an integrated dual-frequency IVUS system with interleaved sampling and parallel signal processing based on FPGA was developed. The central frequency of low-frequency channel is up to 10MHz, and the peak voltage range is 80-200V. The central frequency of the high-frequency channel is up to 60MHz, and the voltage peak-to-peak range is 40-80V. The acquisition channel is 500MHz and 12bit, which is realized by interleaved sampling of two ADC. The motor controlled ultrasonic transducer acquires 400-800 lines per turn, and eventually form a 360-degree IVUS hybrid imaging successfully.

Sound Field Visualization of Specified Frequency by Combining Scanning System with Lock-in Amplifier

Abstract Sound field visualization of specified frequency is an essential method for acoustic studies, especially in nonlinear acoustics. In this paper, we designed a sound field visualization system of specified frequency (SVSF). By combining the traditional sound field scanning system with the lock-in amplifier (LIA), the SVSF can visualize the amplitude distribution of multiple arbitrary specified frequencies with only one-time sound field scanning. Further, depending on the SVSF, we analysed the nonlinear acoustic effects around the focus of a spherical coronal ultrasonic transducer array. The excitation signal is a sinusoidal signal at 40 kHz. The results show that the acoustic waves at the focus contain fundamental frequencies at 40 kHz and harmonic frequencies at 80 kHz, 120 kHz, and 160 kHz. Comparing the amplitude distribution of those frequencies, we found that higher harmonics own smaller focus areas as well as lower amplitude, which conforms to the nonlinear acoustic theory. The system is convenient for those similar studies involving the multi-frequency amplitude field comparison.

A novel theoretical analysis method for the longitudinal cascaded piezoelectric transducer based on equivalent circuit

Abstract High power ultrasonic transducers are widely used in the fields of ultrasonic cleaning, ultrasonic welding and therapeutic ultrasound. To further improve the ultrasonic intensity and power of piezoelectric transducers for power ultrasound applications, the cascaded piezoelectric transducer have received tons of attention. The electromechanical equivalent circuit, as a classical transducer analysis method, translates the structural and mechanical parameters into the corresponding circuit parameters and helps us to better understand and analyze the performance characteristics of the transducer, which is of great significance for the design and optimization of the transducer. In this paper, a new theoretical analysis method based on the equivalent circuit is proposed for cascaded piezoelectric transducer. In this method, the equivalent circuit of each component of the longitudinal piezoelectric transducer is cascaded, and equivalent circuit is analyzed using the Kirchhoff’s law to obtain the frequency resonance equation of the piezoelectric transducer. This analysis method avoids the complex equivalent transformation of the equivalent circuit including multiple excitation sources and also obtains the vibration velocity of the piezoelectric transducer radiation surfaces, more information on the vibration characteristics of the transducer was gained from the theoretical aspect. Finally, the theoretical analysis results are compared with the finite element simulation analysis and the traditional analysis results for verification.

In vitro experimental study on interventional ultrasound-mediated microbubble cavitation lithotripsy

Abstract Ultrasound-mediated microbubble cavitation lithotripsy as a new minimally invasive approach has received great attention for the treatment of urinary stones. However, the attenuation of ultrasonic waves in human tissues and stone displacement during lithotripsy are two key issues limiting the development of this technology. In this paper, a method of interventional ultrasound-mediated microbubble cavitation lithotripsy is proposed, which can realize the in-situ delivery of ultrasonic waves and microbubbles. A piezoelectric ultrasound transducer with the center frequency of 461 kHz and output peak to peak acoustic pressures of 3.2 MPa is fabricated, and microbubbles with the concentration of 1.33×109/ml are synthesized. An extracorporeal experiment platform is built and in vitro tests of ultrasound mediated microbubble cavitation lithotripsy are conducted by using microbubbles with different concentrations and water. The results show that the proposed interventional ultrasound-mediated microbubble cavitation lithotripsy is an efficient method for the fragmentation of ureteral stones. The maximum mass reduction of the stone is 9.4 mg within 30 minutes of treatment under the combined action of ultrasound with the peak-negative pressure of 1.6 MPa and center frequency of 461 kHz and microbubbles with the concentration of 3.325×107/ml. The research results will provide a technical basis for further optimization of subsequent tentative schemes, in vivo experiments with animals and future clinical applications.

A comparison of handheld versus cart-based ultrasound in the evaluation and diagnosis of carpal tunnel syndrome

BackgroundCarpal tunnel syndrome (CTS) is responsible for over 90 % of median nerve neuropathies. Though a clinical diagnosis, evaluation of nerve conduction via electrodiagnostic studies (EDX) and median nerve cross sectional area (CSA) through sonographic imaging provides supporting evidence and insight into disease severity. The advent of handheld ultrasound devices offers a portable, cost-effective and non-invasive method for median nerve assessment, yet its accuracy compared to traditional cart-based ultrasound has not been assessed in this setting. Methods43 consecutive patients who presented to an outpatient orthopedic clinic within a large academic institution for symptoms consistent with CTS between August 2023 and April 2024 were included. Handheld sonography was performed with the Clarius Convex L20 HD3 8–20 MHz transducer. The GE Venue Go with a 4–20 MHz linear transducer was used for conventional cart-based ultrasound evaluation. A paired t-test was performed to compare the mean cross-sectional area (CSA) measured with the GE machine to the mean CSA measured with the Clarius transducer (p < 0.05). ResultsThe average CSA measurement obtained with the GE was 14.21 ± 4.89 mm2. The average CSA measurement obtained with the Clarius handheld transducer was 13.54 ± 4.50 mm2. The mean difference between the GE and Clarius groups was 0.62 mm2 (95 % CI = −1.47 to 2.71), p = 0.55. ConclusionCSA measurements of the median nerve obtained by a handheld ultrasound transducer are comparable to those measured by a traditional cart-based ultrasound machine for carpal tunnel diagnosis. The adoption of handheld ultrasounds in clinical settings holds the potential for quicker, more precise diagnoses and broader access to imaging.

Diagnostic Dilemmas in Fetal Scalp Cystic Lesions: A Case Series

AbstractFetal Scalp cystic lesions are occasionally encountered during the routine mid trimester scan. Some may be benign scalp cysts like an epidermal or dermal cyst, and some may contain neural tissue with associated calvarial defects like meningocele or encephalocele. Prenatally, differentiating them and arriving at an exact diagnosis is challenging. This case study describes seven cases diagnosed with fetal scalp cysts and normal intracranial anatomy. Seven cases with normal intracranial anatomy were included. Out of seven cases, four turned out to be scalp cysts, two turned out to be meningocele, and one was atretic encephalocele. Of four cases of scalp cysts, three regressed spontaneously and one required surgical excision. All instances of meningocele and encephalocele required surgical correction. In the case of fetal scalp cystic lesions, the presence of normal intracranial anatomy and head circumference, the absence of other associated anomalies, and the use of high frequency ultrasound transducers to rule out calvarial defects can aid in delineating the diagnosis of benign fetal scalp cysts.

Vehicle Autonomous Driving System

Autonomous vehicles or self-driving cars industry and technology have played an important role in research industry and automotive industry. Autonomous cars are those vehicles have the ability to sense there surrounding and navigate and drive themselves on roads through traffic without human interventions. In other words, they can move from one location to another one without human interaction. In this paper, an autonomous vehicle system prototype is proposed. The vehicle is able to sense its surrounding and keep going on the road on its own through traffic and other barriers such as people and traffic lights. That is, the vehicles are able to drive and detect the road signals and take decision accordingly, whether to continue or to make a turn. The proposed system uses raspberry pi microcontroller and ultrasonic sensors to detect any object, obstacle, or pedestrians in front of the vehicle and to measure the distance. In addition, a raspberry pi camera is connected to the raspberry pi to continuously take pictures of the road. These pictures will be analyzed by the raspberry pi microcontroller. The vehicle is able to reach its destination safely. A self-driving car prototype has been designed and implemented. The porotype autonomous vehicle system was tested and performed as expected.

Online ultrasonic monitoring of FDM nozzle temperature based on metamaterial buffer rod

Abstract Fused deposition modeling (FDM) has been widely used for fabricating parts with complex geometries. However, during the printing process the nozzle temperature fluctuates which may cause nozzle blockage, inter-filament delamination, over-melting, etc. Therefore, it is of significance to develop an online and in-situ nozzle monitoring system which could overcome such drawbacks for quality assurance. In this work, a multifunctional system is designed by incorporating a traditional ultrasonic probe and a metamaterial buffer rod to online monitor the nozzle temperature and ensure a correct extrusion force and speed. A parametric simulation model is first constructed implicitly based on thermal-acoustic metamaterial structures for the buffer rod. Secondly, since the high-fidelity calculation is computationally expensive, an efficient surrogate model with kriging approach is constructed based on the dataset drawn from limited trials for rapid prediction. Thirdly, multidisciplinary optimization is performed by the NSGA-III algorithm considering the thermal insulation performance, ultrasonic attenuation and structure integrity. The rod is fabricated according to the best parameters decided. A cross-correlation algorithm is calibrated with thermocouple measurement after waveform recording at different temperatures. The online and in-situ temperature measurement can be realized during 3D printing successfully eventually. This will help to improve the printing quality with potential feedback strategies.

Photoacoustic/ultrasound dual-modality imaging of Sentinel lymph node with carbon nanoparticles

Abstract Sentinel lymph node (SLN) biopsy is a widely used method for identifying axillary lymph node metastasis in breast cancer patients, offering an avoidance of unnecessary axillarydissections and a lower incidence of lymphedema and other complications. However, the nuclide localization has added complexity to the procedure due to its accessibility. Methylene blue and other small molecule dyes have been widely used due to their convenience, but they have been found to have lower specificity and sensitivity. Carbon nanoparticles (CNPs), as a new type of tracer, are safe and show improved specificity. However, the significant optical absorption in human tissues still renders the detection of deep lymph nodes challenging. To overcome these challenges, we developed a high-sensitivity ultrasound probe optimized for photoacoustic imaging. Based on the new probe, we constructed a high-sensitivity photoacoustic/ultrasound dual-modality imaging system. A pilot clinical study has been conducted on two patients, preliminarily verifying the system’s ability to locate SLN when combined with the CNPs.

Single-Plane Versus Synchronous Biplane Ultrasound Imaging During Vascular Access Procedures: Which Is Better and How Can We Improve?

Highlights Biplane ultrasound imaging reduces need for probe manipulation during procedure. Providers note clinical benefit of biplane ultrasound imaging for vascular access. Biplane disadvantages include probe size, imaging quality, size of the screen. Thorough didactic and practical education is essential for biplane success. Abstract Background: Use of ultrasound guidance for vascular access procedures is commonplace in inpatient and outpatient care settings. Standard ultrasound probes offer the operator a single-plane view, necessitating rotation of probe to attain dual complimentary views. This mechanical probe rotation increases technical difficulty of ultrasound use. The purpose of this study is to evaluate the rate of cannulation success and efficiency of a synchronous biplane ultrasound mode in ultrasound-guided arterial line placement as compared with a standard single-view ultrasound mode in the operating room setting. Methods: Patients scheduled for elective surgery in which a radial arterial catheter would be used for hemodynamic monitoring were approached for consent to this study. Patients were randomized to either undergo placement with single-plane view versus synchronous biplane view; outcomes were recorded. Providers were provided preprocedural ultrasound education as well as the option of a short hands-on experience; their level of experience was noted. Results: Placement time of a peripheral arterial catheter was longer and required more attempts to be successful using synchronous biplane imaging as compared with single-plane imaging across providers of all skill/experience levels. Subjectively, providers noted the benefit of synchronous biplane imaging in vascular access; however, disadvantages including probe size, quality of imaging, and size of the screen were noted. Discussion: Thorough education regarding the use and functionality of biplane synchronous imaging in vascular access is essential. Additional guided-practice time with experienced operators could also be helpful to overcome the challenges observed in this study.

Abstract P444: Radial pulse wave velocity measurement method with dual ultrasound probe for low power wearables

Background: Wearables for continuous blood pressure monitoring hold the promise to drastically improve hypertension management, but current solutions still lack the required accuracy. Ultrasounds might be able to overcome this limitation because they can measure quantitative parameters highly correlated with blood pressure, such as artery diameter, its motion over the cardiac cycle (AWM) and local pulse wave velocity (PWV). Here we validate radial PWV measurement with an ultrasound method that can be integrated in low power wearables. Methods: The study was conducted on 8 healthy subjects at rest. The ultrasound scan was performed on the left arm with a research scanner and two linear probes held at a fixed distance and used to image two transversal sections of the radial artery at 11.5 kHz for 10 seconds. The first image of each section is segmented to identify the artery walls and AWM is reconstructed by tracking the phase of the wall echo. PWV is extracted from the delay of artery wall motion waveforms on the 2 sections. Reference values of carotid-radial PWV were acquired with Diatecne PulsePen ETT immediately after the ultrasound acquisition on the same arm. Results: The estimate and accuracy of the local radial PWV of proposed ultrasound method is in agreement with the reference carotid-radial PWV obtained with the tonometer. The accuracy of the methods is estimated from the beat-to-beat variability of the delays between the waves used for the estimates. Conclusions: The proposed method allows to measure the radial pulse wave within shorter distances compatible with integration in wearables. Leveraging TDK ultrasound MEMS platform, this paves the route for low power wearable for continuous cardio-vascular monitoring.

Mechanical properties and damage characterization of 310S steel using laser ultrasonic inspection under extreme temperature condition

Abstract To evaluate the mechanical properties of 310S stainless steel under extreme working conditions, and realize the damage characterization function, in this study, the longitudinal wave and Rayleigh wave of materials are measured by the method of coaxial inspection on reverse surface and ipsilateral ectopic inspection, respectively, and surface cracks and internal voids are detected by the scanning laser source technology and transmission scanning detection, respectively. The detection methods are designed based on the energy distribution characteristics of Rayleigh wave and longitudinal waves in laser ultrasound. The laser ultrasonic detection systems coupled with a temperature loading device (high temperature: vacuum chamber; low temperature: refrigerating chamber) developed by the laboratory enable on-site monitoring of laser ultrasonic technology in harsh environments. Experimental results demonstrate that the error in mechanical properties (elastic modulus, shear modulus, Poisson ratio) is less than 5% over a wide temperature range (-180-1000°C). At 1000°C, surface cracks wider than 0.5mm and deeper than 1.9mm as well as internal hole defects larger than 1.0mm can be detected with an error rate below 5%.

Microcontroller-based track axle counter system design

Abstract Axle counting technology is an extremely important part of many aspects in ensuring the safety of railroad operation. Axle counting equipment is set up on the railroad tracks, and through the operation of sensors, it detects the trains that drive into the train operating area where the axle counting equipment is arranged. A common axle counting system uses a detection device that utilizes a wheel sensor that senses the movement of the wheel cutting through magnetic lines of inductance causing a change in the magnetic field within the zone. This paper introduces a track axle counter system, the system will be a microcontroller as the core, the use of ultrasonic detection in the train interval of the train wheel distance changes, instead of the existing axle counting system using wheel sensors to sense the electromagnetic signals generated by the wheels, to achieve the axle counting and counting function, so as to determine the track occupancy.

Autonomous Robot Navigation Using Adaptive Potential Field

This work presents a novel approach to mobile robot autonomous navigation, utilizing enhanced artificial potential fields in conjunction with path planning,obstacle avoidance and SLAM . In traditional adaptive potential fields, which integrate sensor data to enable robots to navigate safely and efficiently through various environments. The robot's perception of its surroundings, obtained through sensors like cameras, ultrasonic devices, is processed to create a dynamic potential field that reflects the spatial distribution of obstacles, goals, and other relevant features.We propose the design and implementation of an autonomous robot-based real-time vision-based system for detecting and tracking features in a structured environment ensuring robust obstacle avoidance and path planning. Keywords- Adaptive Potential Fields, Autonomous Navigation, Autonomous Systems, Machine Learning in Robotics, Motor driver, Obstacle Avoidance, Path Planning, Raspberry Pi, Real-time Adaptation, ROS (Robot Operating System), Sensor-based Navigation, Servo Motor, SLAM (Simultaneous Localization and Mapping),Ultrasonic Sensors

Fine-Tuning of Optical Resonance Wavelength of Surface-Micromachined Optical Ultrasound Transducer Arrays for Single-Wavelength Light Source Readout.

This article reports the fine-tuning of the optical resonance wavelength (ORW) of surface-micromachined optical ultrasound transducer (SMOUT) arrays to enable ultrasound data readout with non-tunable interrogation light sources for photoacoustic computed tomography (PACT). Permanent ORW tuning is achieved by material deposition onto or subtraction from the top diaphragm of each element with sub-nanometer resolution. For demonstration, a SMOUT array is first fabricated, and its ORW is tuned for readout with an 808 nm laser diode (LD). Experiments are conducted to characterize the optical and acoustic performances of the elements within the center region of the SMOUT array. Two-dimensional and three-dimensional PACT (photoacoustic computed tomography) is also performed to evaluate the imaging performance of the ORW-tuned SMOUT array. The results show that the ORW tuning does not degrade the optical, acoustic, and overall imaging performances of the SMOUT elements. As a result, the fine-tuning method enables new SMOUT-based PACT systems that are low cost, compact, powerful, and even higher speed, with parallel readout capability.

Performance and mechanism of carbon sequestration of air-entraining wet shotcrete

CO2 curing concrete technology refers to the CO2 reacts with cement clinker minerals to obtain high-performance concrete and achieve the purpose of energy saving and emission reduction. The researches of air entrainment agent (AEA) focus on the development of new AEA and the study of concrete performance after adding some AEA. In the background of CO2 curing concrete technology, there are relatively few researches on the influence mechanism of different characteristics of bubbles introduced by different AEAs on carbon fixation performance of concrete. This paper demonstrates the characteristics of air bubbles introduced by SY-5 AEA (main component: triterpene saponin) and LAS AEA (main component: sodium dodecylbenzene sulfonate), compares the strength of concrete mixed with above two types of AEAs cured for 28 days and analyzed them by carbonization depth test, ultrasonic detection of fissure test, SEM, XRD and TG. Results show that different AEAs introduced different characteristics of air bubbles, which affected the internal pore characteristics of concrete, and then affected its mechanical properties and carbon sequestration properties. Compared with SY-5 AEA, LAS AEA had a slightly lower air-entraining effect. But the bubbles introduced were even and stable, the internal pores of the hardened concrete were uniform. Although the former had a high carbon sequestration, the latter had a higher intensity at 28 d, about 2.69 % higher. Under carbonization curing conditions, the improvement of concrete properties was more evident when appropriate AEAs were incorporated. The compressive strength and the splitting strength were increased by 5.57 % and 4.5 % respectively under the carbonization curing condition.

Automatic PAUT crack detection and depth identification framework based on inspection robot and deep learning method

Orthotropic steel bridge decks (OSD) are widely acclaimed for their lightweight, high load-carrying capacity, and adaptability, making them a popular choice in steel structure bridges. However, the complex nature of their structure makes them susceptible to fatigue cracking, posing significant safety concerns. To address the issues above, this study employs a robot equipped with an ultrasonic phased array probe to automate the detection of internal cracks within Orthotropic Steel Decks (OSD). A Deep Convolutional Generative Adversarial Network (DCGAN) is utilized to augment the training dataset of Phased Array Ultrasonic Testing (PAUT) images. The YOLO series algorithms are applied and compared for crack localization, with YOLO v7-tiny exhibiting the highest accuracy and speed. Integrating attention mechanisms into the YOLO v7-tiny algorithm to facilliate rapid and high-precision crack detection. Analyzing the echo region with an echo intensity bar enabled the identification of crack depth, with an identification error within 5%.

Design, Fabrication, and Characterization of Capacitive Micromachined Ultrasonic Transducers for Transcranial, Multifocus Neurostimulation.

In a recent study using 3-D fullwave simulations, it was shown for a nonhuman primate model that a helmet-shaped 3D array of 128 transducer elements can be assembled for neurostimulation in an optimized configuration with the accommodation of an imaging aperture. Considering all acoustic losses, according to this study, for a nonhuman primate skull, the assembly of the proposed transducers was projected to produce sufficient focusing gain in two different focal positions at deep and shallow brain regions, thus providing sufficient acoustic intensity at these distinct focal points for neural stimulation. This array also has the ability to focus on multiple additional brain regions. In the work presented here, we designed and fabricated a single 15 mm diameter capacitive micromachined ultrasonic transducer (CMUT) element operating at 800 kHz central frequency with a 480 kHz 3 dB bandwidth, capable of producing a 190 kPa peak negative pressure (PNP) on the surface. The corresponding projected transcranial spatial peak pulse average intensity (ISPPA) was 28 Wcm-2, and the mechanical index (MI) value was 1.1 for an array of 128 of these elements.