Conventional Transducers Research Articles

CRISPR–Cas Systems Associated with Electrolyte-Gated Graphene-Based Transistors: How They Work and How to Combine Them

In this review, recent advances in the combination of CRISPR–Cas systems with graphene-based electrolyte-gated transistors are discussed in detail. In the first part, the functioning of CRISPR–Cas systems is briefly explained, as well as the most common ways to convert their molecular activity into measurable signals. Other than optical means, conventional electrochemical transducers are also developed. However, it seems that the incorporation of CRISPR/Cas systems into transistor devices could be extremely powerful, as the former provides molecular amplification, while the latter provides electrical amplification; combined, the two could help to advance in terms of sensitivity and compete with conventional PCR assays. Today, organic transistors suffer from poor stability in biological media, whereas graphene materials perform better by being extremely sensitive to their chemical environment and being stable. The need for fast and inexpensive sensors to detect viral RNA arose on the occasion of the COVID-19 crisis, but many other RNA viruses are of interest, such as dengue, hepatitis C, hepatitis E, West Nile fever, Ebola, and polio, for which detection means are needed.

Research on the Characteristics of High-Performance Textured Ceramic Materials and Their Application in Composite Rod Transducers

Recently, textured piezoelectric ceramics have become a hot topic in the field of piezoelectric materials. Due to their high cost-effectiveness, textured ceramics are expected to be the material of choice for the next generation of acoustic transducers. In this study, we investigated the coercive field (Ec), piezoelectric constant (d33), and dielectric constant (ε33) of textured PIN-PSN-PT ceramics under different torques, in response to the demand for the development of composite rod transducer technology for transmitting and receiving. Based on the obtained data, a wideband composite rod transducer was designed and fabricated using textured PIN-PSN-PT ceramics with high performance. Compared with conventional PZT piezoelectric ceramic transducers of the same size, the wideband composite rod transducer made with textured ceramics extends the frequency band to a lower frequency of 6.5 kHz, improves the emission performance by 2 dB, and enhances the reception performance by 2 dB. Compared with conventional PZT piezoelectric ceramics in the same frequency band, the acoustic performance is comparable, but there is a volume reduction of 59.23% and a weight reduction of 49.7%, solving the technical bottleneck of developing composite rod transducers that are miniaturized and lightweight. The research results of this study have important reference value for the engineering application of textured ceramic materials in acoustic transducers.

Simulation and Optimization of Transmitting Transducers for Well Logging.

Piezoelectric transducers are commonly used in acoustic well logging. However, the low frequency and narrow range of the acoustic waves limit the achievable detection accuracy. In addition, the low amplitude of the waves causes useful information to be easily masked by noise during detection, which affects the accuracy of geological identification and makes it difficult to detect formations tens of meters away. This paper proposes a microporous liquid-electric transmission transducer, in which the microporous electrode structure generates a powerful shock wave through a high-energy instantaneous discharge. First, a model of the liquid-electric microporous transmitting transducer was constructed by combining simulations with numerical calculations, and its electro-acoustic characteristics were analyzed. Then, based on the survey requirements, two innovative optimization schemes for the microporous electrode structure were proposed, namely a triangular pyramid microporous electrode structure and a rectangular microporous electrode structure, and their performances were compared. The results show that the newly optimized triangular pyramid microporous electrode liquid-electric transducer generates acoustic waves with higher amplitude and a wider frequency range than conventional piezoelectric transducers and other microporous structures. It maintains high energy while achieving high frequencies, enabling detection at distances of up to hundreds of meters and the precise characterization of small geological bodies. This has significant implications for applications in marine exploration, land exploration, clean energy, and new energy fields.

Metallic material microstructure grain size measurements from backscattering signals in ultrasonic array data sets

Ultrasound backscattering signals from material microstructures can be used to evaluate the material microstructure grain size. This typically involves making pulse-echo immersion measurements at multiple locations using a focused ultrasonic transducer in order to obtain an accurate estimate of the root-mean-square amplitude of the back-scattered signal at a specified focal position. However, this restricts some practical applications of using such techniques in, for example, on-line measurements in high-value manufacturing and in-service inspections where multiple immersion measurements are not feasible to use. The main benefit of using ultrasonic phased arrays is that one array probe at one position can focus ultrasound beams at multiple points using different focal laws either physically or in data postprocessing. Potentially this means that accurate grain size measurements can be obtained from a single array measurement. In this paper, the classic backscattering method for conventional transducers is adapted to be used for full matrix capture datasets from an ultrasonic array. Three-dimensional ultrasonic models are developed in the proposed inverse process to measure material microstructure grain size. Experimental validations were performed on two metallic materials: copper (EN1652) and bright mild steel (BS970). A good agreement is shown between the experimentally measured grain sizes from array data and metallography measurements. Compared to the classic pulse-echo immersion back-scattering measurements, the proposed method enables accurate measurement of grain size in a direct contact configuration at fewer locations. This has potential to make on-line grain size measurements possible.

Development of PMUT based ultrasonic gas flowmeter with conical transducer cavities for the validation of industrial standards

The recessed installation of transducers in ultrasonic gas flowmeters (USFMs) creates cylindrical transducer cavities that induce local flow distortions and vortex formations, resulting in significant measurement uncertainty. Currently, USFMs with small diameters predominantly rely on conventional bulk-PZT ultrasonic transducers, which are relatively large and hinder the optimization of vortices. Miniaturized piezoelectric micromachined ultrasonic transducers (PMUTs) present an effective solution for mitigating vortex effects; however, their acoustic performance is constrained by the sensor area, resulting in PMUT-based USFMs that fail to meet industrial measurement requirements. This article introduces a small-diameter USFM utilizing a single PMUT element integrated with the specially designed conical transducer cavity. This design effectively reduces the half-power beamwidth (HPBW) of the single PMUT element to one-fifth of its original size and increases the transmit signal amplitude by 7.2 dB. Computational fluid dynamics (CFD) simulations demonstrate that the conical transducer cavity optimizes vortex distribution within the cavity, reducing vortex intensity. The experimental result demonstrates that the proposed USFM achieves an indicated error of less than ±1 % and repeatability of less than 0.5 %, which meets the class 1.5 accuracy level. This design fully complies with the accuracy standards set in GB/T 39841–2021, validating the PMUT-based USFM for industrial flow measurement.

CMUT for ultrafast passive cavitation detection during ultrasound-induced blood–brain barrier disruption: proof of concept study

Objective.Cavitation dose monitoring plays a key role in ultrasound drug delivery to the brain. The use of capacitive micromachined ultrasonic transducer (CMUT) technology has a great potential for passive cavitation detection (PCD).Approach.Here, a circular (diameter 7 mm) CMUT centered at 5 MHz was designed to be inserted into a therapeutic transducer (1.5 MHz) used for ultrasound-induced blood-brain barrier (BBB) disruption on mice. CMUT-based real-time cavitation detection was performed during the ultrasound procedure (50μl intravenous injection of SonoVue microbubbles, frequency 1.5 MHz, PNP 480 kPa, duty Cycle 10%, PRF 10 Hz, duration 60 s). BBB disruption were confirmed by contrast-enhanced 7T-MRI.Main results.The CMUT device has a fractional bandwidth of 140%, almost twice a conventional piezocomposite PCD transducer. As expected, the CMUT device was able to detect the occurrence of harmonic, subharmonic and ultraharmonic frequencies as well as the increase of broadband signal indicating inertial cavitation in a wide frequency range (from 0.75 to 6 MHz). Signal-to-noise ratio was high enough (>40 dB) to perform ultrafast monitoring and follow the subtle intrapulse variations of frequency components at a rate of 10 kHz.Significance. This firstin vivoproof of concept demonstrates the interest of CMUT for PCD and encourages us to develop devices for PCD in larger animals by integrating an amplifier directly to the CMUT front-end to considerably increase the signal-to-noise ratio.

Association Between Arterial Pulse Waveform Analysis and Mortality in Patients With Septic Shock: A Retrospective Cohort Study Using Japanese Diagnosis Procedure Combination Data.

Purpose: Specialized pressure transducers for arterial pulse waveform analysis (S-APWA) devices are dedicated kits connected to an arterial pressure catheter that monitors hemodynamic parameters, such as cardiac output, pulse pressure variation, and stroke volume variation, less invasively. While the association between the use of S-APWA devices and clinical outcomes in perioperative patients has been previously evaluated, its assessment in patients with septic shock remains inadequate. Materials and Methods: This retrospective cohort study utilized a nationwide Diagnosis Procedure Combination database in Japan. Adult patients with septic shock admitted to the intensive care unit (ICU) with arterial pressure catheter placement on the admission day from August 2012 to February 2021 were included. Hospitalizations meeting the eligibility criteria were categorized into groups based on S-APWA device usage. The primary outcome, evaluated using Cox regression analysis, was 30-day all-cause mortality in the propensity score overlap-weighted population. Secondary outcomes included in-hospital mortality, ICU duration, and overall hospital stay. Results: Among 5130 eligible hospitalizations, 643 were in the S-APWA group and 4487 were in the conventional pressure transducer group. Cox regression analysis within the propensity score overlap-weighted population showed no significant difference in 30-day mortality (adjusted hazard ratio: 0.94; 95% confidence interval: 0.9-1.38; P = .58). Logistic regression analysis indicated no significant differences in the in-hospital mortality. While the S-APWA group had prolonged ICU stays, no significant difference in the overall hospital stay was observed according to linear regression analyses. Conclusions: Our study found no significant association between S-APWA use and 30-day mortality in patients with septic shock. These findings offer insights into optimizing monitoring systems in ICUs.

Synthetic aperture probe and ultrasonic testing

Application of synthetic aperture probes to ultrasonic testing is discussed using as an illustration the dry-contact between two metal surfaces. Synthetic aperture concept uses the motion of the realistic probe over a target region to provide finer spatial resolution than conventional realistic transducer. Typically, the larger the aperture, the higher the image resolution is. We compared results, obtained applying synthetic aperture procedure to standard spherically focused probe with goal to synthesize the large aperture, and results, obtained using novel cylindrically focused transducer with real large aperture. Obtained experimental results confirmed efficiency of synthetic aperture concept in time domain and frequency domain.

Radiation Impedance of Rectangular CMUTs.

Recently, capacitive micromachined ultrasound transducers (CMUTs) with long rectangular membranes have demonstrated performance advantages over conventional piezoelectric transducers; however, modeling these CMUT geometries has been limited to computationally burdensome numerical methods. Improved fast modeling methods, such as equivalent circuit models, could help achieve designs with even better performance. The primary obstacle in developing such methods is the lack of tractable methods for computing the radiation impedance of clamped rectangular radiators. This paper presents a method that approximates the velocity profile using a polynomial shape model to rapidly and accurately estimate radiation impedance. The validity of the approximate velocity profile and corresponding radiation impedance calculation was assessed using finite element simulations for a variety of membrane aspect ratios and bias voltages. Our method was evaluated for rectangular radiators with width:length ratios from 1:1 up to 1:25. At all aspect ratios, the radiation resistance was closely modeled. However, when calculating the radiation reactance, our initial approach was only accurate for low aspect ratios. This motivated us to consider an alternative shape model for high aspect ratios, which was more accurate when compared with FEM. To facilitate the development of future rectangular CMUTs, we provide a MATLAB script that quickly calculates radiation impedance using both methods.

Monitoring of cementitious materials hydration using 2–2 cement-based piezoelectric transducers based on electromechanical impedance method

Monitoring cementitious materials hydration enhances construction efficiency by providing crucial information regarding the optimal timing for shoring removal and pre-stress transferring. In recent years, many scholars have utilized the lead zirconate titanate (PZT)-based electromechanical impedance method (EMI) to monitor the cementitious materials hydration process. However, conventional piezoelectric transducers are less compatible with cementitious materials. In addition, the currently commonly used statistical-based metrics lack a clear physical meaning. The 2–2 cement-based transducer (2−2), composed of multiple PZT elements, demonstrates excellent electromechanical performance and good compatibility with cementitious materials. In this study, the 2–2 was employed to monitor the cementitious materials hydration, and an electromechanical impedance model for describing the interaction between the 2–2 and the structure was presented. Taking into account both resonance frequency and peak value of the conductance signatures, an objective function was defined. Genetic algorithm (GA) was employed to minimize the disparity between theoretical and experimental results, thus extracting equivalent stiffness and damping. The empirical relationship between equivalent stiffness, damping, and compressive strength was established to predict the compressive strength. The experimental results show that for the same monitoring process, the normalized equivalent stiffness and damping extracted from different 2–2 sensors are in some agreement. It is more sensitive to hydration processes than statistical indicators. More importantly, the equivalent parameters have a clear physical meaning and can better portray the hydration process of the cementitious materials.

Investigation of an Active Focusing Planar Piezoelectric Ultrasonic Transducer.

Ultrasonic focusing transducers have broad prospects in advanced ultrasonic non-destructive testing fields. However, conventional focusing methods that use acoustic concave lenses can disrupt the acoustic impedance matching condition, thereby adversely affecting the sensitivity of the transducers. In this paper, an active focusing planar ultrasonic transducer is designed and presented to achieve a focusing effect with a higher sensitivity. An electrode pattern consisting of multiple concentric rings is designed, which is inspired by the structure of Fresnel Zone Plates (FZP). The structural parameters are optimized using finite element simulation methods. A prototype of the transducer is manufactured with electrode patterns made of conductive silver paste using silk screen-printing technology. Conventional focusing transducers using an acoustic lens and an FZP baffle are also manufactured, and their focusing performances are comparatively tested. The experimental results show that our novel transducer has a focal length of 16 mm and a center frequency of 1.16 MHz, and that the sensitivity is improved by 23.3% compared with the conventional focusing transducers. This research provides a new approach for the design of focusing transducers.

An ultrasonic transducer focusing ultrasound into a thin waveguide by two elliptical reflectors

A high-power ultrasonic transducer for minimally invasive treatments is proposed, capable of treating areas inaccessible by high-intensity focused ultrasound treatments. This transducer employs two elliptical reflectors that efficiently focus ultrasound waves into a thin waveguide by utilizing mode conversion. Additionally, a slit structure is introduced to suppress wave diffraction, further enhancing the focusing capabilities of the transducer. Finite element analysis demonstrates that the proposed transducer achieves an impressive energy density magnification factor of 325, with an energy efficiency of 24.2 %. This efficiency is 3.4 times higher than that of a conventional transducer, Double Parabolic refLector wave-guided Ultrasonic transducer.

Design and experimental validation of a broadband multi-modal coupled capsule-shaped transducer for underwater acoustics

This paper introduces a novel approach to expand the working frequency band of underwater acoustic transducers through multi-modal coupling. We designed a broadband multi-modal coupled piezoelectric capsule-shaped transducer structure by leveraging the advantages of conventional piezoelectric spherical-shell and piezoelectric cylindrical-tube transducers. First, the finite element method (FEM) was employed to scrutinize the influence of key structural parameters on the acoustic performance of the capsule-shaped transducer, thereby establishing the foundation for the final transducer design. Subsequently, the designed transducer was characterized through modal analysis and harmonic response analysis of electrical-mechanical-acoustical multiphysics field coupling. Finally, a prototype of the capsule-shaped transducer was fabricated and measured, with the results compared with those of a spherical-shell transducer. A comparative analysis of the measured outcomes revealed that the capsule-shaped transducer exhibits coupling among three modes within the frequency range of 10 kHz to 30 kHz. The transmitting voltage response (TVR) values exceeded 143.5 dB, reaching a maximum of 151.9 dB, and the working frequency bandwidth achieved 18 kHz. Compared with the spherical-shell transducer, the average TVR value demonstrates a 3.7 dB improvement, and the bandwidth exhibited an 8.4 % increase. According to the experimental findings, the proposed capsule-shaped piezoelectric transducer offers advantages such as high voltage response, a broad working frequency band, compact size, low weight, and easy installation. This technology can be further applied to small underwater platforms, enhancing their acoustic detection range and spatial coverage performance.

Rayleigh wave excitation with an elliptical reflector for high-power ultrasound

This study proposes a Rayleigh wave transducer with an elliptical reflector for high-power ultrasound (ELIPS). In contrast to conventional transducers using IDT with single crystal piezoelectric plates or wedge transducers, our ELIPS enables high-power Rayleigh wave excitation in the megahertz range, which will be useful for applications such as surface acoustic wave (SAW) motors, SAW tactile devices, and SAW atomizers. The driving principles of the transducer are Rayleigh wave excitation with a transverse wave source and transverse wave focusing with a dilatational wave source and an elliptical reflection surface. The effectiveness of this mechanism was confirmed with an FEM simulation, and the Rayleigh wave excitation was validated using a prototype transducer. Finally, the high-power characteristics were examined, and a maximum vibration amplitude of 15.5 nm at 1.0 MHz was successfully obtained. It should be noted that this vibration amplitude is not a saturated value, and a much higher value could be realized with higher input power.

A novel strategy of concrete monitoring: The application of the integrated sensing element (ISE)

This study strategically provides an innovative pattern for concrete monitoring at the service and deterioration stages by the integrated sensing element (ISE). The advantage of the ISE is that it can independently respond to loading variation and cooperate with other sensors. The results show that the ISE can independently identify the cracking state, monitor stress conditions, and distinguish the creep behavior of concrete with different compressive strength levels. By applying this novel monitoring pattern, the relationships between stress and relative velocity change (∆v/v) can be accurately traced; meanwhile, concrete with different creep degrees can be identified. Additionally, by tracing the de-correlation coefficients (Kd), this study also reveals that the binding behavior between sensors and concrete has a significant impact on signal variation. Specifically, the maximum Kd value derived from the signal of ISE at the loading process (46.5% of the maximum uniaxial compressive strength) is lower than 0.1, while that value derived from the signal of the conventional contact transducers can exceed 0.5. At a short-time fixed loading experiment, the Kd values derived from the signal of ISE show no significant increasing trend.

Multipoint Energy-Balanced Laser-Ultrasonic Transducer Based on a Thin-Cladding Fiber.

This study proposes a novel multipoint transducer system by utilizing the single-mode-multimode-thin-cladding fiber (SMTC) structure. This structure leverages the disparity in mode field diameter between the multimode fiber (MMF) and thin-cladding fiber (TCF) to generate high-amplitude ultrasonic signals safely and efficiently. The fabricated transducer exhibits signal amplitudes 2-3-fold higher compared to conventional laser-ultrasonic transducers. Simulation analysis investigates the impact of the length of the MMF and the diameter of the TCF on coupling efficiency. The coupling efficiency of individual transducer units can be accurately controlled by adjusting the length of the MMF. A three-point energy-balanced laser-ultrasonic transducer system was achieved, with improved energy conversion efficiencies, and the optimal thickness of candle soot nanoparticles (CSNPs) is experimentally determined. Additionally, we carried out experiments to compare the performance of the proposed SMTC-based transducer system under different material conditions using two different photoacoustic materials: graphite-epoxy resin and candle soot nanoparticle-polydimethylsiloxane (CSNP-PDMS) composite. CSNPs, as a cost-effective and easy-to-prepare composite material, exhibit higher photoacoustic conversion efficiency compared to graphite-epoxy resin. The proposed system demonstrates the potential for applications in non-destructive testing techniques.

A Novel Nondestructive Testing Probe Using AlN-Based Piezoelectric Micromachined Ultrasonic Transducers (PMUTs).

Ultrasonic nondestructive testing (NDT) usually utilizes conventional bulk piezoelectric transducers as transceivers. However, the complicated preparation and assembly process of bulk piezoelectric ceramics limits the development of NDT probes toward miniaturization and high frequency. In this paper, a 4.4 mm × 4.4 mm aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT) array is designed, fabricated, characterized, and packaged for ultrasonic pulse-echo NDT of solids for the first time. The PMUT array is prepared based on the cavity silicon-on-insulator (CSOI) process and packaged using polyurethane (PU) material with acoustic properties similar to water. The fabricated PMUT array resonates at 2.183 MHz in air and at around 1.25 MHz after PU encapsulation. The bandwidth of the packaged PMUT receiver (244 kHz) is wider than that of a bulk piezoelectric transducer (179 kHz), which is good for axis resolution improvement. In this work, a hybrid ultrasonic NDT probe is designed using two packaged PMUT receivers and one 1.25 MHz bulk transmitter. The bulk transmitter radiates an ultrasonic wave into the sample, and the defect echo is received by two PMUT receivers. The 2D position of the defect could be figured out by time-of-flight (TOF) difference, and a 30 mm × 65 mm detection area is acquired. This work demonstrates the feasibility of applying AlN PMUTs to ultrasonic NDT of solids and paves the way toward a miniaturized NDT probe using AlN PMUT technology.

An ultrasensitive and broadband transparent ultrasound transducer for ultrasound and photoacoustic imaging in-vivo

Transparent ultrasound transducers (TUTs) can seamlessly integrate optical and ultrasound components, but acoustic impedance mismatch prohibits existing TUTs from being practical substitutes for conventional opaque ultrasound transducers. Here, we propose a transparent adhesive based on a silicon dioxide-epoxy composite to fabricate matching and backing layers with acoustic impedances of 7.5 and 4–6 MRayl, respectively. By employing these layers, we develop an ultrasensitive, broadband TUT with 63% bandwidth at a single resonance frequency and high optical transparency ( > 80%), comparable to conventional opaque ultrasound transducers. Our TUT maximises both acoustic power and transfer efficiency with maximal spectrum flatness while minimising ringdowns. This enables high contrast and high-definition dual-modal ultrasound and photoacoustic imaging in live animals and humans. Both modalities reach an imaging depth of > 15 mm, with depth-to-resolution ratios exceeding 500 and 370, respectively. This development sets a new standard for TUTs, advancing the possibilities of sensor fusion.

Predicting the coefficient of friction in a sliding contact by applying machine learning to acoustic emission data

It is increasingly important to monitor sliding interfaces within machines, since this is where both energy is lost, and failures occur. Acoustic emission (AE) techniques offer a way to monitor contacts remotely without requiring transparent or electrically conductive materials. However, acoustic data from sliding contacts is notoriously complex and difficult to interpret. Herein, we simultaneously measure coefficient of friction (with a conventional force transducer) and acoustic emission (with a piezoelectric sensor and high acquisition rate digitizer) produced by a steel–steel rubbing contact. Acquired data is then used to train machine learning (ML) algorithms (e.g., Gaussian process regression (GPR) and support vector machine (SVM)) to correlated acoustic emission with friction. ML training requires the dense AE data to first be reduced in size and a range of processing techniques are assessed for this (e.g., down-sampling, averaging, fast Fourier transforms (FFTs), histograms). Next, fresh, unseen AE data is given to the trained model and the resulting friction predictions are compared with the directly measured friction. There is excellent agreement between the measured and predicted friction when the GPR model is used on AE histogram data, with root mean square (RMS) errors as low as 0.03 and Pearson correlation coefficients reaching 0.8. Moreover, predictions remain accurate despite changes in test conditions such as normal load, reciprocating frequency, and stroke length. This paves the way for remote, acoustic measurements of friction in inaccessible locations within machinery to increase mechanical efficiency and avoid costly failure/needless maintenance.

On the strength of the piezoceramic transducer in the system of structural health monitoring

The aim of the presented paper is the more detailed investigation and improvement of pre-stressing technology for the piezoelectrical transducer (PET) protection from degradation at action of extreme overload and longtime variable load in operation. Earlier developed 1D model of embedded PET is verified by the finite element analysis. Using this model, the parametrical assessment of stress state and strength of conventional transducer is done. It is shown that there is specific class of PET for which satisfying solution cannot always be obtained by optimization of parameters of the conventional piezoelectrical transducer (CPET). Therefore, further analysis is focused on the stress state and strength of the pre-stressed piezoelectrical transducer (PPET) it comparison with CPET. The electromechanical impedance (EMI) and its integral indicis are used for assessment of PET operability. Numerical simulation of EMI response to possible damages of PET and the outcome of static and fatigue tests are shown the significantly higher resistance of PPET against operational degradation in comparison with CPET.