Search Results (870)

This paper presents a fully automated platform for real-time monitoring of fatigue-induced microstructural changes in metallic materials, using Rayleigh surface waves and Laser Doppler Vibrometry (LDV). The system integrates ultrasonic excitation, non-contact optical sensing, and high-speed signal processing in a unified LabVIEW environment. Rayleigh waves are generated via a contact transducer, while LDV captures surface vibrations with sub-nanometric velocity resolution, ensuring repeatability and eliminating coupling variability. The software automates synchronization, deterministic data acquisition, filtering, FFT analysis, and extraction of nonlinear coefficients (β₂, β₃) at high execution rates without the need for post-processing. Experimental validation under cyclic loading revealed a clear sensitivity hierarchy: the Rayleigh wave velocity remained invariant, the acoustic attenuation responded gradually, while the nonlinear parameters exhibited the earliest and steepest response to fatigue damage, confirming their superiority as early-stage indicators. The system offers low-latency timing, long-term stability, and modular design, establishing a robust data-streaming foundation that can support future integration with digital twin frameworks and machine learning models. Furthermore, the acoustic findings were successfully cross-validated using Infrared Thermography, which confirmed the critical damage transition phase. This work bridges nonlinear acoustics and software automation, providing a scalable diagnostic solution for predictive maintenance within structural health monitoring systems. Full article

Musculoskeletal (MSK) pain is a prevalent clinical condition that significantly impairs quality of life, and current treatment options are not effective on all patients or have severe, long-term side effects. Sustained Acoustic Medicine (SAM) delivers therapeutic ultrasound, providing diathermic and mechanical stimulation to local tissue and facilitating healing. Additionally, therapeutic ultrasound has been shown to enhance transdermal drug delivery via sonophoresis. Cannabidiol (CBD) is a small molecule that has been shown to have anti-inflammatory effects drug delivery. However, CBD has never been studied in conjunction with therapeutic ultrasound, and its potential effects on ultrasound efficacy are unknown. Therefore, this study compares standard high viscosity ultrasound (US) gel and commercially available CBD gel both in terms of acoustic properties and in an ex vivo bovine muscle model with SAM treatment. The acoustic properties of CBD & US gels were measured using a hydrophone, an oscilloscope and a function generator. The function generator propagated a pulsed wave through each gel, and the time between the original and reflected waves was used to determine the acoustic coefficients. Then, a SAM transducer was positioned and placed into the coupling bandage and gel depot on the bovine muscle with 3 mL of US gel or CBD gel. Tissue was stimulated by SAM for 240 min with a 60-min cooldown, and internal muscle temperatures at 1 cm, 2 cm, and 5 cm were continuously monitored. US gel and CBD had no significant differences in their acoustic properties. There were no significant differences in the change in temperature for SAM treatment with CBD gel compared to SAM treatment with US gel at 1 cm (Δ12.06 ± 1.04 °C vs. Δ12.52 ± 1.84 °C, p > 0.05), 2 cm (Δ8.13 ± 1.01 °C vs. Δ8.97 ± 1.04 °C, p > 0.05), and 5 cm (Δ4.83 ± 0.91 °C vs. Δ3.83 ± 0.66 °C, p > 0.05). CBD gel does not compromise SAM’s ultrasonic delivery and diathermic efficacy, making this combination a novel option for musculoskeletal rehabilitation. Future studies could explore changes in transdermal CBD delivery with SAM treatment for deep tissue delivery. Full article

Capacitive micromechanical ultrasonic transducers (CMUTs), as microelectromechanical systems (MEMS) devices, have broad application prospects in ultrasonic imaging and sensing. This study investigates the influence of surface acoustic waves (SAWs) using periodically arranged CMUTs as the fundamental unit cells. We first utilize finite element analysis (FEA) to calculate and analyze the band structure and bandgap characteristics of phononic crystals under infinite periodic conditions. Subsequently, for finite periodic structures in practical applications, acoustic transmission spectra were further simulated using FEA to verify the bandgap characteristics of the structure for SAWs. Accordingly, this paper leverages a deep learning framework based on a multilayer perceptron (MLP) architecture to achieve the inverse design and optimization of CMUT geometric parameters, tailored to specific target bandgap requirements. The results demonstrate that this approach can efficiently and accurately determine the optimal structural configurations, offering a robust and novel technical paradigm for the precise control of SAWs using CMUT-based periodic arrays. Full article

Acoustic emission (AE) monitoring in metal additive manufacturing (AM) requires compact sensors capable of high-frequency operation, broad bandwidth, and high sensitivity. However, increasing structural stiffness to achieve high resonance frequencies typically reduces electromechanical sensitivity. This work presents a finite element study of a coupled-resonator capacitive micromachined ultrasonic transducer (CMUT) designed to address this trade-off. The proposed architecture integrates three mechanically coupled silicon membranes with a stepped capacitive cavity that increases capacitance while preserving structural stiffness, enabling enhanced sensitivity without compromising high-frequency operation. COMSOL Multiphysics simulations were used to evaluate modal characteristics and frequency response under DC pre-stressed conditions. Modal coupling produced closely spaced resonances that broadened the effective bandwidth, while the stepped cavity significantly increased voltage output through improved electromechanical coupling. Compared to a single-resonator flat-cavity design, the coupled stepped-cavity configuration demonstrated nearly a threefold enhancement in output voltage while maintaining operation near 100 kHz. Additionally, adjusting the central resonator length enabled controlled frequency tuning for scalable array implementation. These results establish a proof of concept for a high-frequency, high-sensitivity micro-electro-mechanical systems (MEMS) CMUT architecture suitable for distributed AE monitoring in advanced manufacturing environments. Full article

This paper addresses the challenge of accurately measuring liquid level interfaces in multiphase mixed media by proposing a detection method based on ultrasonic transmission. First, a mathematical model of the ultrasonic measurement system was established, and the acoustic field characteristics of transducers with different frequencies and diameters in slurry were simulated and analyzed to determine the optimal excitation frequency and probe diameter. On this basis, an echo sound pressure calculation model based on the side-incidence method was constructed, and a formula for calculating the liquid level interface height was derived. Finally, an experimental test platform with a multi-layer steel container was built to measure the propagation velocity, attenuation coefficient, and acoustic impedance coefficient of ultrasound in the slurry, verifying the feasibility of the liquid level interface measurement method. Full article

The miniaturization of medical ultrasound imaging transducers is currently limited by the thick backing layers required to dissipate backward acoustic energy. To address this, a novel hybrid composite backing material was developed by interpenetrating a three-dimensional open-cell nickel foam skeleton with a traditional tungsten-powder/epoxy-resin matrix. Two groups of composite samples with varying pores per inch (PPI) were fabricated, and their acoustic properties were systematically characterized. Experimental results indicated that the 100 PPI composite achieved macroscopic acoustic attenuation coefficients of 62.6 dB/cm at 5 MHz and 84.2 dB/cm at 7.5 MHz. These values are roughly three times higher than conventional backing materials, while maintaining a suitable acoustic impedance of 10.81 MRayl. A 5 MHz transducer utilizing a 5.0 mm layer of this proposed backing achieved a −60 dB two-way pulse-echo insertion loss, effectively eliminating backside interference with performance comparable to a 16.5 mm conventional backing. This structural strategy successfully reduces the required backing axial dimension by over 60% without compromising transducer bandwidth, offering a viable material solution for miniaturized ultrasonic transducers. Full article

A novel broadband ultrasonic transducer design based on a non-uniform-thickness double-layer piezoelectric structure and a variable-thickness matching layer is proposed to overcome the limitations of conventional thickness-mode piezoelectric ultrasonic transducers, such as weak even-order harmonic responses and restricted bandwidth. The implementation of a non-uniform-thickness double-layer piezoelectric structure enables the simultaneous excitation and reception of ultrasonic signals containing both fundamental and second-harmonic frequencies. Furthermore, through the integration of variable-thickness matching layers with a backing material of non-uniform acoustic impedance, the dual resonant frequency responses are effectively merged into a broad bandwidth. The broadband transducer prototype is manufactured and characterized through electrical input impedance, time-domain pulse-echo signals, and corresponding frequency spectrum. Experimental results indicate a center frequency of 411.5 kHz, with dual resonant peaks observed near 298.6 kHz and 585.6 kHz, achieving a −6 dB relative bandwidth of 116%. The findings demonstrate that the self-developed broadband transducer is capable of effectively generating and receiving broadband signals containing both fundamental and second-harmonic components, thereby offering a new design strategy for broadband piezoelectric transducers. Full article

A capacitive micromachined ultrasonic transducer (CMUT) was engineered and functionalized with either zeolitic imidazolate framework-8 (ZIF-8) dispersed in an AZ1512HS photoresist matrix or with graphene oxide (GOx) to operate as a gravimetric sensor for organic vapors. The sensor response was investigated under controlled humidity conditions during pulsed exposure to acetone, ethyl methyl ketone, isopropanol, kerosene, and diesel vapors. The impedance of the device was monitored by observing and tracking the resonance frequency shift as well as the resistance maximum shift, giving us the possibility to track two response parameters simultaneously. Different combinations of shifts in the sensor resonance frequency and the resistance maximum values were observed for the ZIF-8 functionalized device when exposed to the selected vapors, ranging from 12.4 kHz for ethyl methyl ketone to 2.4 kHz for diesel, and from 580 Ω for acetone to 20 Ω for isopropanol. Sensors functionalized with GOx did not demonstrate any significant response to either ethyl methyl ketone or isopropanol in the frequency domain. GOx-functionalized sensors were used for relative humidity monitoring in test gases. Besides the conventional response of the produced gravimetric sensing system, we also observed a strong relationship between the humidity of the gas mixture and the strength of the interaction of target gases with the functional film of the sensor. The results highlight the multidimensional nature of the sensor response and demonstrate how humidity influences the interaction between vapor molecules and the functional coating. This paper focuses on the characterization of the coupled behavior of resonance frequency and resistance shifts under controlled operating conditions. The presented experimental setup provides a basis for future concentration-dependent investigations and functional material comparisons in CMUT-based gravimetric sensing systems and provides a necessary foundation for accurate interpretation of future concentration-resolved measurements. Full article

Capacitive micromachined ultrasonic transducers (CMUTs) have been developed over the past 30 years and achieved practical applications in both medical imaging and industrial non-destructive testing. This article presents the fundamental principles of CMUTs and surveys fabrication technologies, offering a comprehensive review of major advances and challenges in medical ultrasound and photoacoustic imaging applications. The article further reviews and analyzes three primary challenges currently confronting CMUTs in medical imaging applications: lower output acoustic pressure, dielectric charging effects, and the need for high bias voltage. It also presents and discusses a potential combined approach to comprehensively address these challenges, with the aim of enhancing CMUT performance and broadening clinical adoption. Full article

Ensuring the durability and safety of modern infrastructure critically depends on the quality and strength of concrete. The Ultrasonic Pulse Velocity (UPV) method is a widely used non-destructive testing technique for evaluating concrete properties; however, factors such as aggregate size distribution, compaction methods, and surface quality can significantly influence UPV results and their correlation with compressive strength. This study investigates the effects of different aggregate sizes and an innovative vibration-assisted compaction method—developed using piezoelectric (PZT) transducers—on the mechanical, ultrasonic, and surface properties of concrete. Four distinct aggregate size distributions were employed to produce sixteen concrete specimens with constant mix proportions. Unlike conventional low-frequency, high-power vibration practices, a high-frequency (40 kHz), low-power (120 W) vibration protocol was applied through PZT elements placed within the molds to enhance compaction and reduce entrapped air. Experimental results indicated that the heaviest specimen (7.13 kg) was the medium-aggregate sample compacted using tamping and rodding methods. The highest UPV value (4143 m/s) was obtained from the coarse-aggregate specimen subjected to three minutes of vibration. In contrast, the best compressive strength performance (22.73 MPa) was observed in the medium-aggregate specimen without any vibration treatment. The findings revealed that both aggregate size and advanced vibration techniques have significant effects on the mechanical properties, ultrasonic response, and surface quality of concrete. In addition, a proof-of-concept portable surface-finishing prototype consisting of a steel plate instrumented with multiple PZT transducers was developed, and preliminary trials qualitatively suggested improved surface leveling when applied in contact with the concrete surface. Surface roughness was quantified via image processing (Light Map 150 and Specular Map 150). The rough-area fraction decreased from ~29.8% in the untreated specimen to ~4.3% after ultrasonic application, indicating a marked improvement in surface leveling and overall surface quality. The results indicate that the applied PZT vibration protocol did not improve compressive strength; in several cases, particularly under prolonged excitation, a reduction in strength was observed. In contrast, a significant improvement in surface quality was achieved, with the rough-area fraction decreasing from approximately 29.8% to 4.3%. However, due to the limited number of specimens, the findings should be interpreted as preliminary. Overall, the method appears more promising as a surface enhancement technique rather than a direct alternative to conventional compaction methods. Full article

Multifrequency operation in micromachined ultrasonic transducers, enabled by targeted excitation of specific vibrational modes, has emerged as an attractive approach for achieving tunable performance and configurability, well-suited for advanced ultrasound imaging and therapeutic applications. This paper presents a dual-electrode rectangular piezoelectric micromachined ultrasonic transducer (PMUT) designed for efficient dual-frequency operation through mode-selective actuation. The proposed architecture employs segmented electrodes that are spatially aligned with the strain distributions of two distinct flexural modes, enabling selective excitation of Mode 1 (fundamental) and Mode 3 (higher order) through appropriate electrode actuation. Finite element simulations and impedance analysis were used to guide the electrode configuration and validate the mode-selective behavior. The dual-mode PMUT was fabricated alongside a conventional single-electrode PMUT using identical membrane dimensions and material stack for direct comparison. Comprehensive electrical and underwater acoustic characterization confirmed that the conventional PMUT is limited to single-frequency operation at the fundamental resonance. In contrast, the proposed design achieved a substantial improvement in higher-order performance, with a threefold increase in acoustic pressure at Mode 3 compared to the conventional device. These results demonstrate that mode-aligned electrode segmentation enables efficient dual-mode operation without added fabrication complexity, making the design highly suitable for multifrequency ultrasonic applications such as biomedical imaging and sensing. Full article

The failure of impedance matching between the ultrasonic power supply and the transducer can degrade machining quality, decrease machining efficiency, and reduce tool life. To enhance the detection efficiency of impedance matching status in ultrasonic machining systems, an impedance matching detection method based on the Voltage Standing Wave Ratio (VSWR) is proposed. First, by constructing a fitting model for the forward and reverse voltage and power of ultrasonic power supply, the relationship between VSWR and voltage is determined. Subsequently, a correlation model between the VSWR and tool tip amplitude, which reflects the working state of the ultrasonic system, is established. And the range of VSWR for optimal performance of system impedance matching is obtained by means of the model. Finally, the detection effectiveness of this method is verified through experiments on tool tip output amplitude under varying working conditions, and a comparison is made between this method and the phase method. The results indicate that using VSWR as a detection parameter to characterize impedance matching yields measurement values within 7% of the theoretical values. These results confirm the evaluation interval for a good working state of the system. Furthermore, experiments under varying force loads and temperatures demonstrate the reliability of the VSWR-based characterization. Compared to the traditional phase method, this approach reduces the cost of impedance matching performance detection and meets the requirements for impedance matching status detection during ultrasonic machining. Full article

This work investigates how ultrasonic vibration can enhance friction stir welding (FSW) of an AA6082-T6 aluminium alloy and develops a data-driven tool to predict joint performance from process settings. A custom ultrasonic transducer and horn were designed and tuned using finite element modal and harmonic analyses, confirming a strong longitudinal resonance near 27.9 kHz with a tip amplitude of about 46 µm. A 27-run factorial experiment varied tool rotation (600–900 rpm), welding speed (45–55 mm/min), and plunge depth (0.10–0.25 mm). Welded joints were assessed using tensile strength and Vickers hardness. Four predictive models, support vector regression (SVR), Gaussian process regression (GPR), artificial neural networks (ANNs), and multiple linear regression (MLR) were trained and compared under five-fold cross-validation. The best joint quality was obtained at 900 rpm, 55 mm/min, and a 0.25 mm plunge depth, yielding a tensile strength of 188.7 MPa and a hardness of 102 HV. Overall, MLR provided the strongest predictive performance while remaining interpretable (UTS R² = 0.81, RMSE = 11.84 MPa; hardness R² = 0.67, RMSE = 2.36 HV), matching the ANN for UTS prediction and outperforming the ANN, GPR, and SVR for hardness. A coupling physics-based ultrasonic design with an interpretable predictive model offers a practical route to reduce trial and error, improve parameter selection, and accelerate the process development for ultrasonic vibration-assisted FSW of aluminium alloys; however, modest models can outperform complex ones when the dataset is limited. Full article

The detection of micro-defects within cemented carbides necessitates a high-frequency, high-sensitivity ultrasonic non-destructive testing transducer (UNDTT), whose performance is highly sensitive to geometric structural parameters. Conventional design approaches rely heavily on empirical trial-and-error, resulting in low efficiency and difficulty in achieving globally optimal solutions. To address this limitation, an intelligent multi-objective optimization method is proposed for transducer structural parameters—namely, radius, matching layer thickness, and backing layer thickness—to simultaneously maximize sensitivity ($V_{pp}$), center frequency ($f_c$), and bandwidth (BW). By investigating the relationship between structural parameters and performance metrics, a dataset was constructed and used to develop a convolutional neural network (CNN) surrogate model that captures their nonlinear mapping. The CNN was integrated with the NSGA-III multi-objective optimization algorithm to iteratively generate a Pareto-optimal solution set, from which the best design was selected using the entropy-weighted Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). Finite element analysis (FEA) validation confirmed prediction errors below 7.0%. Compared to conventional designs, the proposed approach delivers a 46.1% higher sensitivity and a 7.7% broader bandwidth while maintaining a thinner matching layer. These results confirm the effectiveness and practical advantage of the proposed framework. This data-driven approach offers an efficient alternative for designing a high-performance UNDTT. Full article

This review paper provides a comprehensive overview of the functional materials and assembly technologies used in intracardiac echocardiography (ICE) and intravascular ultrasound (IVUS) transducers. ICE and IVUS are advanced medical imaging technologies that play significant roles in the diagnosis and treatment of cardiovascular diseases, involving material selection and fabrication processes for miniature piezoelectric ultrasonic transducers. The review begins with an introduction to the principles and applications of ICE and IVUS, highlighting their advantages over other imaging modalities, then delves into the materials and assembly processes of the transducers, presenting the mainstream trends and research progress in various directions in this field in recent years. Finally, the paper summarizes the future technological development and clinical application trends of ICE/IVUS ultrasonic transducers. Full article