Array Of Piezoelectric Transducers Research Articles

A single‐inductor self‐powered SECE interface circuit for dynamic load multi‐PZTs energy harvesting

AbstractThere is always considerable inconsistency between the input energy and the amount of the energy required for the load in piezoelectric transducers (PZTs) energy harvesting interface circuits that often degrades the harvesting performance of most of them. Multiple piezoelectric transducers (multi‐PZTs) vibration scavenging may address this issue by enhancing input power and, consequently, environmental adaptability and reliability. The proposed interface circuit may extract energy from a PZT array regardless of each PZT amplitude, frequency, or phase, even under dynamic or heavy load circumstances. The circuit is thoroughly simulated by LTSpice software and evaluated by post‐simulation calculations and discussions. The simulation findings demonstrate that the proposed self‐powered (SP) SECE‐based multi‐PZT EH interface circuit, named MI‐SP‐SECE, can extract a peak power of 12.8 µW from three PZTs in the provided actual scenario at a dynamic load regime with a simulated excitation of 1.5 g and 50 Hz. The proposed circuit's energy integration and harvesting efficiencies are 75% and 85%, respectively. It can achieve a power enhancement of 2.8× relative to a multi‐input full‐bridge rectifier. In addition, the proposed circuit is scalable effectively because it requires just one inductor component.

A study of the ultrasonic and audible frequency response of commercial loudspeakers for use as parametric acoustic arrays

Parametric acoustic loudspeakers (PAL), also known as parametric acoustic arrays (PAA), are speakers that use ultrasonic waves to generate directive audible sound. They emit an ultrasonic carrier modulated in amplitude by the desired audible signal, and due to non-linear propagation in air, this signal is reproduced in the audible range. Typical applications include audio reproduction for entertainment, but also active noise control and acoustic measurement of material properties. PAA typically consist of an array of piezoelectric transducers set on a surface. However, there are other speakers in the market that, due to their characteristics, could also achieve the PAL effect. This work examines the performance of commercial speakers when reproducing. First, the ultrasonic frequency response of each speaker is examined in free-field conditions using exponential sine sweeps (ESS). This enables searching for potential carrier frequencies to modulate the ESS in the ultrasonic range. The ESS are next modulated in the desired ultrasonic region and emitted through each speaker, obtaining their audible and ultrasonic impulse responses. The results show that some commercial speakers can also operate as PALs, which is interesting from an industrial point of view as it lowers costs and simplifies the assembly process.

Micropower design of energy harvesting based on piezoelectric transducer array circuit

Micropower design of energy harvesting based on piezoelectric transducer array circuit

Design and on-site alert effect of piezoelectric device with amplified displacement for improving clean-energy collection

The installation of road alert devices leads to increased power consumption and electric network complexity on roads, which can be mitigated by cantilever piezoelectric transducers applicable to self-powered road alert devices. However, currently the cantilever piezoelectric transducer does not match the actual pavement deformation. In view of this, the link-type stroke amplification mechanism for road was designed. Then, the factors influencing the magnification were clarified and the size parameters were optimized. Finally, the performance of the piezoelectric transducer array under the amplification mechanism was investigated, and the traffic alert application effect of the amplified displacement road piezoelectric device was tested. The results showed that: The end connecting rod with short length and small distance and the middle connecting rod with longer length were favorable to the magnification. The theoretical magnification of the fabricated stroke amplification mechanism is 2.0. Under its action, the 0.7 mm excitation displacement could result in piezoelectric transducer array electrical outputs of 48 V, 103.96 mW, and power densities of 32.1 W/m2. And the alert piezoelectric self-powered effect was good based on the actual road test. The results will help improve the level of road alert self-powered, and promote the development of clean energy on the road.

Relating Hydro‐Mechanical and Elastodynamic Properties of Dynamically Stressed Tensile‐Fractured Rock in Relation to Applied Normal Stress, Fracture Aperture, and Contact Area

AbstractWe exploit nonlinear elastodynamic properties of fractured rock to probe the micro‐scale mechanics of fractures and understand the relation between fluid transport and fracture aperture under dynamic stressing. Experiments were conducted on rough, tensile‐fractured Westerly granite subject to triaxial stresses. We measure fracture permeability for steady‐state fluid flow with deionized water. Pore pressure oscillations are applied at amplitudes ranging from 0.2 to 1 MPa at 1 Hz frequency. During dynamic stressing we transmit ultrasonic signals through the fracture using an array of piezoelectric transducers (PZTs) to monitor evolution of interface properties. We examine the influence of fracture aperture and contact area by conducting measurements at effective normal stresses of 10–20 MPa. Additionally, the evolution of contact area with stress is characterized using pressure sensitive film. These experiments are conducted separately with the same fracture and map contact area at stresses from 9 to 21 MPa. The measurements are a proxy for “true” contact area for the fracture surface and we relate them to elastic properties using the calculated PZT sensor footprints via numerical modeling of Fresnel zones. We compare the elastodynamic response of the fracture using the stress‐induced changes in ultrasonic wave velocities for transmitter‐receiver pairs to image spatial variations in contact properties. We show that nonlinear elasticity and permeability enhancement decrease with increasing normal stress. Additionally, post‐oscillation wave velocity and permeability exhibit quick recoveries toward pre‐oscillation values. Estimates of fracture contact area (global and local) demonstrate that the elastodynamic and permeability responses are dominated by fracture topology.

Wave Propagation for Structural Health Monitoring (WaveProSHM): open software with GUI

Guided wave–based SHM methods have been explored extensively in recent decades. The wave propagation modelling including piezoelectric transducers and various damage types helps understand intricacies of guided wave behavior and for designing a robust SHM system. However, modelling aspects are still challenging. Moreover, commercially available software for the modelling of guided waves often lacks appropriate high-order elements and code optimization for fast GPU computations. This research aimed to develop and disseminate to the SHM community the open software based on highly efficient vectorised code of the time domain spectral element method which can be run on GPU. The developed code is written in MATLAB with Graphical User Interface (GUI) and communicates with GMSH – open source finite element mesh generator. It can model signals of propagating guided waves in structures which are excited and registered by an array of piezoelectric transducers. The capabilities of the software are shown in an example of a large-scale problem of interacting guided waves with delamination.

Structural Health Monitoring of Composite Leaf Spring Using Guided Elastic Waves

The integration of advanced materials, such as fiber-reinforced composites, has transformed numerous industries by offering lightweight and high-performance solutions. In the context of automotive applications, these composites enable producing more efficient vehicles. Nevertheless, there are still uncertainties regarding operational safety. Potential emergence of barely visible damages such as fiber fracture, delamination, and debonding accounts for a limited lifespan of the composite components. To address these concerns, permanent monitoring offers a compelling solution, enabling the early detection of damage, thus reducing maintenance costs and the risk of failures regarding human life. In this sense, guided waves based Structural Health Monitoring (SHM) has demonstrated promising results. However, it has so far primarily remained in laboratory settings with limited real-life applications due to some challenges, such as the costs involved and the transparency of results. This contribution focuses on the development of permanent monitoring of a novel spring leaf component manufactured of a carbon and glass fiber-reinforced composite. To establish permanent structural monitoring, piezoelectric transducer arrays have been integrated into the composite spring leaf structure during manufacturing. The placement of these transducers is determined through sensitivity analysis, considering ultrasound wave propagation characteristics. After a series of measurements, state-of-the-art damage identification methods customized to designed SHM setup are employed and compared. Outcomes are discussed with an emphasis on the efficient detection of narrow body composite structures. Additionally, damage detection evaluation of low-sensitive areas in such structures are explored in particular. While reliability assessment and compensation of environmental effects have been left for future research, this study presents tested methods and results, aiming to contribute to the advancement of SHM techniques in practical applications.

Probabilistic impact localization in composites using wavelet scattering transform and multi-output Gaussian process regression

Data-driven machine-learning models offer considerable promise for acoustic source localization. However, many existing models rely on training data that correlates time-of-flight (TOF) measurements with source locations, yet they struggle to handle the complexities arising from nonlinear wave propagation in materials with varying properties. Furthermore, these models overlook the noise and uncertainties inherent in real-world experiments when predicting outputs. This paper aims to bridge a gap in impact localization for such structures, particularly focusing on scenarios involving noisy field measurements. This study proposes a framework based on probabilistic machine learning to identify impact locations, utilizing wavelet scattering transform (WST) and Multi-Output Gaussian Process Regression (moGPR). WST extracts informative features from Lamb waves, capturing relevant signatures for training the probabilistic machine learning model, while moGPR estimates correlated impact location coordinates (x, y) while accounting for inherent uncertainties in the data. To assess the proposed method’s performance in handling measurement uncertainties, an experiment was conducted using a CFRP composite panel instrumented with a sparse array of piezoelectric transducers. The results demonstrate that the probabilistic framework effectively addresses measurement uncertainties, enabling reliable source location estimation with confidence intervals and providing valuable insights for decision-making.

Transdermal drug delivery using low-frequency sonophoresis: COMSOL simulation of piezoelectric array transducers

This study explores the design and simulation of specialized sonophoretic transducers aimed at enhancing the transdermal delivery of large drugs. We examine different elements of the transducer's design, such as the choice of materials, its dimensions, and the matching of acoustic impedance. We selected PZT-4, from the lead zirconate titanate (PZT) group, as the main material due to its excellent piezoelectric features and durability. We also use polymer matrices to make the transducer less rigid. The simulation outcomes, using COMSOL Multiphysics, cover five different transducer array sizes (8x5, 10x6, 12x8, 14x9, and 16x10) within the frequency range of 20-40 kHz. We measure the acoustic pressure at a depth of 0.1 mm under the skin, which is key for successful drug delivery through the skin. Our results show how increasing the size of the array affects the transducer's efficiency. We confirm our simulation results by comparing them with a previously published ANSYS simulation and finding good alignment. This comparison adds reliability to our methods and outcomes. The study also proposes creating a small, wrist-mounted device for drug delivery that could be combined with drug patches, making it user-friendly. Moreover, we stress the need to follow Mechanical Index (MI) guidelines to avoid damaging the skin. Overall, our findings highlight the importance of the array size in the performance of the transducer and confirm the validity of our simulation approach, paving the way for innovative solutions in drug delivery that could have wide applications in healthcare.

Corrosion damage identification based on the symmetry of propagating wavefield measured by a circular array of piezoelectric transducers: Theoretical, experimental and numerical studies

The article investigates the results obtained from numerical simulations and experimental tests concerning the propagation of guided waves in corroded steel plates. Developing innovative methodologies for assessing corrosion-induced degradation is crucial for accurately diagnosing offshore and ship structures exposed to harsh environmental conditions. The main aim of the research is to analyze how surface irregularities affect wave propagation characteristics. An investigation was conducted for antisymmetric fundamental mode A0. Specifically, the study examines the asymmetrical wavefronts generated by nonuniform thickness in damaged specimens. Initially, numerical analysis explores the impact of thickness variation on wave field symmetry. Corroded plates with varying levels of degradation are modeled using the random fields approach, with degradation levels ranging from 0 % to 60 %. Subsequently, the research investigates how the standard deviation of thickness distribution (from 5 % to 20 % of the initial thickness) and excitation frequency (from 50 to 150 kHz) influence recorded signals and the shape of reconstructed wavefronts. Each scenario compares wavefront symmetry levels estimated using rotational and bilateral symmetry degrees as indicative parameters. The numerical simulations are complemented by experimental tests conducted on plates with three different degradation levels. The results demonstrate the efficacy of the proposed wave field analysis approach for assessing structural integrity, as evidenced by the agreement between numerical predictions and experimental observations.

Piezoelectric Micromachined Ultrasonic Transducers with Micro-Hole Inter-Etch and Sealing Process on (111) Silicon Wafer.

Piezoelectric micromachined ultrasound transducers (PMUTs) have gained significant popularity in the field of ultrasound ranging and medical imaging owing to their small size, low power consumption, and affordability. The scar-free "MIS" (micro-hole inter-etch and sealing) process, a novel bulk-silicon manufacturing technique, has been successfully developed for the fabrication of pressure sensors, flow sensors, and accelerometers. In this study, we utilize the MIS process to fabricate cavity diaphragm structures for PMUTs, resulting in the formation of a flat cavity diaphragm structure through anisotropic etching of (111) wafers in a 70 °C tetramethylammonium hydroxide (TMAH) solution. This study investigates the corrosion characteristics of the MIS technology on (111) silicon wafers, arranges micro-pores etched on bulk silicon around the desired cavity structure in a regular pattern, and takes into consideration the distance compensation for lateral corrosion, resulting in a fully connected cavity structure closely approximating an ortho-hexagonal shape. By utilizing a sputtering process to deposit metallic molybdenum as upper and lower electrodes, as well as piezoelectric materials above the cavity structure, we have successfully fabricated aluminum nitride (AlN) piezoelectric ultrasonic transducer arrays of various sizes and structures. The final hexagonal PMUT cells of various sizes that were fabricated achieved a maximum quality factor (Q) of 251 and a displacement sensitivity of 18.49 nm/V across a range of resonant frequencies from 6.28 MHz to 11.99 MHz. This fabrication design facilitates the achievement of IC-compatible and cost-effective mass production of PMUT array devices with high resonance frequencies.

A Lamb-wave based SHM for multi-damage localizations in large composite plates by using piezoelectric transducer array

In this paper, a Lamb-wave based structural health monitoring for multi-damage localizations in large composite plates is presented. The Lamb waves are generated and received by piezoelectric transducers, which are arranged in array on the composite plate. In the experiments, three composite plates with various laminate stacking sequences and taper designs were prepared. The damages were created on the specimens by impact testing. In each specimen, 24 piezoelectric transducers were utilized and mounted on the specimen surface. This study proposed an algorithm to identify the damage localizations. The transducer layout is classified by 10 subsets. In each subset, the wave propagation paths can be grouped into path groups pivoted by actuators and that by sensors. Based on the damage index, the mean angle line for each path group in a subset can be obtained. By assuming that the mean angle line passes through the actual damage, the damage localization can be achieved if there exist more than two mean angle lines in one subset. In this study, two exclusion rules are proposed to exclude a path group from the damage localization calculations. The damage localization results show that, for a composite plate with multiple damages, their locations can be identified by using multiple subsets. The damage localization results show that the damage location can be accurately predicted for the case that a damage exists in the interior of a subset. The experiment results also show that the Lamb wave characteristics and the localization results are not affected by the thickness variation of the plate, indicating that the proposed algorithm is available for tapered composite plate.

Optimum Piezo-Electric Based Energy Harvesting for Low-Power Wireless Networks with Power Complexity Considerations

Low-power wireless sensing-based networks suffer from many constraints and challenges. In this research work, efficient power source has been designed to provide the need of energy for the Wireless Sensor Networks (WSNs) and Wireless Body Area Networks (WBANs). The energy sources are the main challenge and constraint these wireless networks applications. This paper discusses recent researcher’s works which considered the energy constraints of the WSN and WMSN with their proposed security techniques. The main idea of this presented work is the energy harvesting through extracting the electrical energy from the audio/acoustic signal/energy, this utilized audio/acoustic source in this scenario is the disk jockey. To maximize the produced power from the proposed acoustic energy harvesting Piezo-based several parameters is studied. The parameters are considered in this research work are the method of Piezo-transducers connections, the distance of sound source, the sound intensity variation and the sound concentrating tube length. These tubes are mounted on slim diaphragm two maximize the energy harvesting. The piezoelectric transducer array scenario is designed using four piezoelectric transducers utilizing different connect ion methods, series, parallel and in hybrid. Several practically experiments are performed on the presented different scenarios to evaluate the proposed energy harvesting efficiency. These experiments reveal that the superiority of the proposed acoustic energy harvesting technique with low power complexity wireless networks and suitable with the different presented scenarios.

Photoacoustic imaging of visually evoked cortical and subcortical hemodynamic activity in mouse brain: feasibility study with piezoelectric and capacitive micromachined ultrasonic transducer (CMUT) arrays.

This study investigates the feasibility of capturing visually evoked hemodynamic responses in the mouse brain using photoacoustic tomography (PAT) and ultrasound (US) dual-modality imaging. A commercial piezoelectric transducer array and a capacitive micromachined ultrasonic transducer (CMUT) array were compared using a programmable PAT-US imaging system. The system resolution was measured by imaging phantoms. We also tested the ability of the system to capture visually evoked hemodynamic responses in the superior colliculus as well as the primary visual cortex in wild-type mice. Results show that the piezoelectric transducer array and the CMUT array exhibit comparable imaging performance, and both arrays can capture visually evoked hemodynamic responses in subcortical as well as cortical regions of the mouse brain.

Wearable ultrasound bioelectronics for healthcare monitoring

Wearable ultrasound bioelectronics for healthcare monitoring

A probabilistic framework for source localization in anisotropic composite using transfer learning based multi-fidelity physics informed neural network (mfPINN)

The practical application of data-driven frameworks like deep neural network in acoustic emission (AE) source localization is impeded due to the collection of significant clean data from the field. The utility of the such framework is governed by data collected from the site and/or laboratory experiment. The noise, experimental cost and time consuming in the collection of data further worsen the scenario. To address the issue, this work proposes to use a novel multi-fidelity physics-informed neural network (mfPINN). The proposed framework is best suited for the problems like AE source detection, where the governing physics is known in an approximate sense (low-fidelity model), and one has access to only sparse data measured from the experiment (high-fidelity data). This work further extends the governing equation of AE source detection to the probabilistic framework to account for the uncertainty that lies in the sensor measurement. The mfPINN fuses the data-driven and physics-informed deep learning architectures using transfer learning. The results obtained from the data-driven artificial neural network (ANN) and physics-informed neural network (PINN) are also presented to illustrate the requirement of a multi-fidelity framework using transfer learning. In the presence of measurement uncertainties, the proposed method is verified with an experimental procedure that contains the carbon-fiber-reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers. The results conclude that the proposed technique based on a probabilistic framework can provide a reliable estimation of AE source location with confidence intervals by taking measurement uncertainties into account.

A Baseline-Free Lamb Wave Damage Localization Method Based on Compressed Sensing

In conventional Lamb wave-based damage detection, estimation is generally performed using the difference between the measured and baseline signals. However, it is difficult to maintain consistent measurement conditions between the measured and baseline signals, likely leading to large measurement errors. This paper proposed a baseline-free Lamb wave-based detection method for locating damage to structures. The damage scattering waves are extracted according to their features in the frequency-wavenumber spectrum and the damage locations are visualized using probability imaging. To reduce the complications of full wavefield acquisition, wavefield data are acquired using piezoelectric transducer (PZT) arrays at sampling rates much lower than the Nyquist frequency, and the original wavefield is reconstructed by applying compressed sensing. Experimental results on an aluminum plate indicate that the proposed method can provide the damage probability at each plate position without requiring a reference signal, suggesting its applicability to damage diagnosis of structures. Moreover, the proposed method achieves a compression ratio of 86.7% compared with the use of Nyquist sampling.

Multiperspective Photoacoustic Imaging Using Spatially Diverse CMUTs.

Photoacoustic imaging (PAI) is a promising technique to assess different constituents in tissue. In PAI, the propagating waves are low-amplitude, isotropic, and broadband. A common approach in PAI is the use of a single linear or curved piezoelectric transducer array to perform both PA and ultrasound imaging. These systems provide freedom, agility, and versatility for performing imaging, but have limited field of view (FOV) and directivity that degrade the final image quality. Capacitive micromachined ultrasonic transducers (CMUTs) have a great potential to be used for PAI since they provide larger bandwidth and better cost efficiency. In this study, to improve the FOV, resolution, and contrast, we propose a multiperspective PAI (MP-PAI) approach using multiple CMUTs on a flexible array with shared channels. The designed array was used to perform MP-PAI in an in vitro experiment using a plaque mimicking phantom where the images were compounded both incoherently and coherently. The MP-PAI approach showed a significant improvement in overall image quality. Using only three CMUTs led to about 20% increase in generalized-contrast-to-noise ratio (gCNR), 2-dB improvement in peak signal-to-noise ratio (PSNR), and double the structural coverage in comparison to a single CMUT setup. In numerical studies, the MP-PAI was thoroughly evaluated for both the coherent and incoherent compounding methods. The assessments showed that the image quality further improved for increased number of transducers and angular coverage. For 15 transducers, the improvement for resolution and contrast could be up to three times the amount in a single-perspective image. Nonetheless, the most prominent improvement of MP-PAI was its ability to resolve the structural information of the phantoms.

Flexible ultrasound transceiver array for non-invasive surface-conformable imaging enabled by geometric phase correction

Ultrasound imaging provides the means for non-invasive real-time diagnostics of the internal structure of soft tissue in living organisms. However, the majority of commercially available ultrasonic transducers have rigid interfaces which cannot conform to highly-curved surfaces. These geometric limitations can introduce a signal-quenching air gap for certain topographies, rendering accurate imaging difficult or impractical. Here, we demonstrate a 256-element flexible two-dimensional (2D) ultrasound piezoelectric transducer array with geometric phase correction. We show surface-conformable real-time B-mode imaging, down to an extreme radius of curvature of 1.5 cm, while maintaining desirable performance metrics such as high signal-to-noise ratio (SNR) and minimal elemental cross-talk at all stages of bending. We benchmark the array capabilities by resolving reflectors buried at known locations in a medical-grade tissue phantom, and demonstrate how phase correction can improve image reconstruction on curved surfaces. With the current array design, we achieve an axial resolution of ≈ 2 mm at clinically-relevant depths in tissue, while operating the array at 1.4 MHz with a bandwidth of ≈ 41%. We use our prototype to image the surface of the human humerus at different positions along the arm, demonstrating proof-of-concept applicability for real-time diagnostics using phase-corrected flexible ultrasound probes.

Development of a 16-Channel Broadband Piezoelectric Micro Ultrasonic Transducer Array Probe for Pipeline Butt-Welded Defect Detection.

Butt welding is extensively applied in long-distance oil and gas pipelines, and it is of great significance to conduct non-destructive ultrasonic testing of girth welds in order to avoid leakage and safety accidents during pipeline production and operation. In view of the limitations of large transducer size, single fixed beam angle, low detection resolution and high cost of conventional ultrasonic inspection technologies, a 16-channel piezoelectric micro ultrasonic transducer (PMUT) array probe was developed through theoretical analysis and structural optimization design. After the probe impedance characterization, the experimental results show that the theoretical model can effectively guide the design of the ultrasonic transducer array, offering the maximum operating frequency deviation of less than 5%. The ultrasonic echo performance tests indicate that the average −6 dB bandwidth of the PMUT array probe can be up to 77.9%. In addition, the fabricated PMUT array probe has been used to successfully detect five common internal defects in pipeline girth welds. Due to the multiple micro array elements, flexible handling of each element, large bandwidth and high resolution of defect detection, the designed PMUT array probe can provide a good application potential in structural health monitoring and medical ultrasound imaging fields.