Search Results (229)

Structural Health Monitoring (SHM) is an essential technique for continuously assessing structural conditions using integrated sensor systems during operation. SHM technologies have evolved to address the increasing demand for efficient maintenance strategies in advanced engineering fields, such as civil infrastructure, aerospace, and transportation. However, developing a miniaturized, cost-effective, and multi-sensor solution based on Wireless Sensor Networks (WSNs) remains a significant challenge, particularly for SHM applications in weight-sensitive aerospace structures. To address this, the present study introduces a novel WSN-based Multi-Sensor System (MSS) that integrates multiple sensing capabilities onto a 3 × 3 cm flexible Printed Circuit Board (PCB). The proposed system combines a Piezoelectric Transducer (PZT) for impact detection; a strain gauge for mechanical deformation monitoring; an accelerometer for capturing dynamic responses; and an environmental sensor measuring temperature, pressure, and humidity. This high level of functional integration, combined with real-time Data Acquisition (DAQ) and precise time synchronization via Bluetooth Low Energy (LE), distinguishes the proposed MSS from conventional SHM systems, which are typically constrained by bulky hardware, single sensing modalities, or dependence on wired communication. Experimental evaluations on composite panels and aluminum specimens demonstrate reliable high-fidelity recording of PZT signals, strain variations, and acceleration responses, matching the performance of commercial instruments. The proposed system offers a low-power, lightweight, and scalable platform, demonstrating strong potential for on-board SHM in aircraft applications. Full article

Phased-array ultrasonic transducers using sol–gel composites face challenges in terms of polarization uniformity when using conventional corona poling. Pb(Zr, Ti)O₃ (PZT)/PZT composites with a thickness of 25 µm were fabricated on 3 mm thick titanium substrates, and the samples were poled by AC poling, DC poling, and corona discharge poling at RT. It was found that the polarization direction could be controlled by the voltage off-phase angle. When poling was performed with a voltage off-phase angle of 90°, applied voltage of 200 V (rms), 10 cycles, and frequency of 1 Hz, average values and standards of measured piezoelectric constant d₃₃ of −35.1 ± 0.8 pC/N and ultrasonic sensitivity of 11.4 ± 0.1 dB were obtained. Furthermore, the AC-poled samples demonstrated smaller variations in d₃₃ and ultrasonic sensitivity compared with the corona-poled samples, and higher values of d₃₃ and ultrasonic sensitivity compared with the DC-poled samples, indicating the potential of AC poling for PZT/PZT sol–gel composites with large areas. Full article

Piezoelectric energy harvesting in roadways can power distributed sensors and electronics by capturing underutilized mechanical energy from traffic. In this research, 1-3 stacked piezocomposites were developed and evaluated to determine optimal designs for multiple applications. The design of these transducers aimed at operating in a multitude of scenarios, under compressive loads (1–10 kN) at low-frequency (10 Hz) applications, intended to simulate vehicular forces. Power comparison was utilized between numerous transducers to determine the most efficient configuration for electromechanical energy conversion. Design guidelines were based on mechanical integrity, output power, active piezoelectric volume percentage, aspect ratio, and geometric factors. The forces applied in this study were reliant on the average vehicle weight. An intermediate PZT volume fraction and moderate pillar aspect ratios were found to yield the highest power output, with the stacked 1-3 composite significantly outperforming a monolithic PZT of a similar size. Full article

In the context of autonomous environmental monitoring, this study investigates a surface acoustic wave (SAW) sensor designed for selective carbon dioxide (CO₂) detection. The sensor is based on a LiTaO₃ piezoelectric substrate with copper interdigital transducers and a polyetherimide (PEI) layer, chosen for its high electromechanical coupling and strong CO₂ affinity. Finite element simulations were conducted to analyze the resonance frequency response under varying gas concentrations, film thicknesses, pressures, and temperatures. Results demonstrate a linear and sensitive frequency shift, with detection capability starting from 10 ppm. The sensor’s autonomy is ensured by a piezoelectric energy harvester composed of a cantilever beam structure with an attached seismic mass, where mechanical vibrations induce stress in a piezoelectric layer (PZT-5H or PVDF), generating electrical energy via the direct piezoelectric effect. Analytical and numerical analyses were performed to evaluate the influence of excitation frequency, material properties, and optimal load on power output. This integrated configuration offers a compact and energy-independent solution for real-time CO₂ monitoring in low-power or inaccessible environments. Full article

This article investigates energy harvesting methods designed to capture energy from the alternating magnetic field surrounding a current-carrying conductor. The study focuses on the use of piezoelectric transducers in both monolithic and bimorph configurations. Experimental tests were conducted using vibrating beam structures composed of a single-layer piezoelectric material as well as bimorph piezoelectric composites, both utilizing lead zirconate titanate (PZT) as the active material. The results demonstrate a significant improvement in energy harvesting efficiency when using the bimorph configuration. Specifically, the bimorph-based system generated a peak voltage of 4.26 V and a current of 127.16 μA, resulting in an RMS power output of 272.48 μW. The operating principles, signal conditioning strategies, and structural differences in the evaluated designs are discussed in detail. The outcomes indicate the potential of such systems for powering autonomous sensors in low-power industrial monitoring applications. Full article

Ultrasonic applications such as non-destructive testing, biomedical imaging or range measurements are currently based on piezoelectric bulk transducers. Yet, these kinds of transducers with their mm to cm dimensions are rather impractical in fields in which both frequencies in the kHz region and small-feature sizes are required. This fact mainly relates to the inverse relationship between the resonance frequency constant and the transducers’ dimension, yielding a higher frequency and attenuation with a decreasing size. Piezoelectric micromachined ultrasonic transducers (PMUTs), in comparison, incorporate a small-scale µm design while preserving the operating frequency in the desired kHz range. This contribution presents the detailed manufacturing of such a PMUT with a multiple ring electrode‑based structure to additionally adjust the sound pressure fields. The PMUT will be characterized by its deflection in air along with the characterization of the piezoelectric material lead zirconate titanate (PZT) itself. The measurements showed a maximum polarization of 21.8 µC/cm² at 50 kV/cm, the PMUT’s displacement of 30.50 nm/V in air when all electrodes are driven, and an adjustable deflection via different electrode excitations without the need for additional hardware. The ring design also offered the possibility to emit two distinct frequencies simultaneously. These results demonstrate the potential of the designs for small-feature-size applications as they are in high demand for implantable devices, miniaturized ultrasonic-based communication or drug delivery. Full article

Distribution cabinets are of paramount importance in power supply systems. Internal partial discharge may result in power interruption or even the outbreak of fire. This paper proposes a partial discharge (PD) detection approach based on a fiber-optic Mach–Zehnder interferometer (MZI). The MZI method utilizes a fiber wound with a certain size and number of turns as the sensing element, which is mounted on the wall of the low-voltage distribution cabinet to monitor the partial discharge within the cabinet in real time. A true-type distribution cabinet partial discharge experimental platform is developed to validate the proposed method. Three 10 m long fiber-optic sensors with diameters of 50 mm, 80 mm, and 100 mm are designed and compared with a traditional piezoelectric transducer (PZT) for analysis. The experimental results indicate that the fiber-optic MZI sensor can effectively capture PD acoustic pulses, and the pulse amplitude is consistent with that of the PZT sensor. Moreover, compared with the PZT sensor, the fiber-optic MZI system possesses a higher frequency response and a longer effective detection time for PD pulses, demonstrating superior PD detection performance. The fiber-optic coil sensor with a diameter of 8 cm performed optimally in the experiment. The fiber-optic sensing method based on the MZI has significant potential application value in the partial discharge detection of power distribution cabinets, providing a theoretical basis for its application in engineering practice. Full article

An emerging alternative to conventional piezoelectric technologies, which continue to dominate the ultrasound medical imaging (US) market, is Capacitive Micromachined Ultrasonic Transducers (CMUTs). Ultrasound transducers based on this technology offer a wider frequency bandwidth, improved cost-effectiveness, miniaturized size and effective integration with electronics. These features have led to an increase in the commercialization of CMUTs in the last 10 years. We conducted a review to answer three main research questions: (1) What are the commercially available CMUT-based clinical sonographic devices in the medical imaging space? (2) What are the medical imaging applications of these devices? (3) What is the performance of the devices in these applications? We additionally reported on all the future work expressed by modern studies released in the past 2 years to predict the trend of development in future CMUT device developments and express gaps in current research. The search retrieved 19 commercially available sonographic CMUT products belonging to seven companies. Four of the products were clinically approved. Sonographic CMUT devices have established their niche in the medical US imaging market mainly through the Butterfly iQ and iQ+ for quick preliminary screening, emergency care in resource-limited settings, clinical training, teleguidance, and paramedical applications. There were no commercialized 3D CMUT probes. Full article

State-of-the-art research on narrow-linewidth external cavity semiconductor lasers has provided limited discussion on the capability of continuous wavelength tuning. In this study, we present a 780 nm tunable external cavity diode laser (ECDL) with narrow linewidth. An angle-adjustable interference filter (IF) is employed as the mode-selection element, enabling a wide wavelength tuning range. Precise, mode-hop-free continuous tuning is achieved through a combination of current modulation and piezoelectric ceramic transducer (PZT) control, with a tuning accuracy of 1.65 pm/mA. Experimental optimization of the interference filter external cavity diode laser (IF-ECDL) operating conditions resulted in a narrow linewidth of 55 kHz and a high output power of 51 mW. Furthermore, by integrating current and PZT tuning, continuous wavelength tuning of the IF-ECDL output is demonstrated over a specified range. Full article

Establishing dependable and resilient methodologies for identifying damage that may compromise the integrity of reinforced concrete (RC) infrastructures is imperative for preventing potential catastrophic failures. Continuous evaluation and Structural Health Monitoring (SHM) can play a key role in extending the lifespan of new or existing buildings. At the same time, early crack detection in critical members prevents bearing capacity loss and potential failures, enhancing safety and reliability. Furthermore, implementing discrete fibers in concrete has significantly improved the ductility and durability of Fiber-Reinforced Concrete (FRC). The present study employs a hierarchical clustering analysis (HCA) to identify damage in FRC by analyzing the raw Electromechanical Impedance (EMI) signature of piezoelectric lead zirconate titanate (PZT) transducers. The experimental program consisted of three FRC standard cylinders subjected to repeated loading. The loading procedure consists of 6 incremental steps carefully selected to gradually deteriorate FRC’s structural integrity. Additionally, three PZT patches were adhered across the height of its specimen using epoxy resin, and their EMI response was captured between each loading step. Subsequently, the HCA was conducted for each PZT transducer individually. The experimental investigation demonstrates the efficacy of HCA in detecting load-induced damage in FRC through the variations in the EMI signatures of externally bonded PZT sensors. Full article

Forcecardiography (FCG) uses force sensors to record the mechanical vibrations induced on the chest wall by cardiac and respiratory activities. FCG is usually performed via piezoelectric lead-zirconate titanate (PZT) sensors, which simultaneously record the very slow respiratory movements of the chest, the slow infrasonic vibrations due to emptying and filling of heart chambers, the faster infrasonic vibrations due to movements of heart valves, which are usually recorded via Seismocardiography (SCG), and the audible vibrations corresponding to heart sounds, commonly recorded via Phonocardiography (PCG). However, PZT sensors are not flexible and do not adapt very well to the deformations of soft tissues on the chest. This study presents a flexible FCG sensor based on a piezoelectric polyvinylidene fluoride (PVDF) transducer. The PVDF FCG sensor was compared with a well-assessed PZT FCG sensor, as well as with an electro-resistive respiratory band (ERB), an accelerometric SCG sensor, and an electronic stethoscope for PCG. Simultaneous recordings were acquired with these sensors and an electrocardiography (ECG) monitor from a cohort of 35 healthy subjects (16 males and 19 females). The PVDF sensor signals were compared in terms of morphology with those acquired simultaneously via the PZT sensor, the SCG sensor and the electronic stethoscope. Moreover, the estimation accuracies of PVDF and PZT sensors for inter-beat intervals (IBIs) and inter-breath intervals (IBrIs) were assessed against reference ECG and ERB measurements. The results of statistical analyses confirmed that the PVDF sensor provides FCG signals with very high similarity to those acquired via PZT sensors (median cross-correlation index of 0.96 across all subjects) as well as with SCG and PCG signals (median cross-correlation indices of 0.85 and 0.80, respectively). Moreover, the PVDF sensor provides very accurate estimates of IBIs, with R² > 0.99 and Bland–Altman limits of agreement (LoA) of [−5.30; 5.00] ms, and of IBrIs, with R² > 0.96 and LoA of [−0.510; 0.513] s. The flexibility of the PVDF sensor makes it more comfortable and ideal for wearable applications. Unlike PZT, PVDF is lead-free, which increases safety and biocompatibility for prolonged skin contact. Full article

Nitrogen dioxide (NO₂) is broadly acknowledged as one of the six key air pollutants, posing a significant threat to environmental stability and human health. The profile of atmospheric nitrogen dioxide is required for quantifying NO₂ emissions from fossil fuel combustion and industry. In continuous-wave differential absorption lidar (CW-DIAL) systems, the laser sources employed are subject to the issues of varying output characteristics and poor instability. This study presents a CW-DIAL system for remote sensing of atmospheric NO₂ that employs a compact grating-based external cavity diode laser (ECDL) and Scheimpflug imaging. The laser in this system utilizes a piezoelectric transducer (PZT) for precise wavelength tuning, emitting at 448.1 nm and 449.7 nm with an output power of 2.97 W and a narrow linewidth of 0.16 nm. Signal capturing was achieved through a Newtonian telescope with a diameter of 200 mm and a 45° inclined CCD image sensor, satisfying the Scheimpflug principle. A case study near road traffic was used to verify the feasibility of ECDL-DIAL, which took place from 1 October to 2 October 2023 over an industrial park. The system generates precise NO₂ distribution maps with sub-50 m resolution over 3 km, updating every 10 min. Full article

Today’s ultrasonic transducers find broad application in diverse technology branches and most often cannot be replaced by other actuators. They are typically based on lead-containing piezoelectric ceramics. These should be replaced for environmental and health issues by lead-free alternatives. Multiple material alternatives are already known, but there is a lack of information about their technological readiness level. To fill this gap, a small series of prestressed longitudinally vibrating transducers was set up with a standard PZT material and two lead-free variants within this study. The entire process for building the transducers is documented: characteristics of individual ring ceramics, burn-in results, and free vibration and characteristics under load are shown. The main result is that the investigated lead-free materials are ready to use within ultrasonic bolted Langevin transducers (BLTs) for medium-power applications, when the geometrical setup of the transducer is adopted. Since lead-free ceramics need higher voltages to achieve the same power level, the driving electronics or the mechanical setup must be altered specifically for each material. Lower self-heating of the lead-free materials might be attractive for heat-sensitive processes. Full article

For those piezoelectric materials that operate under high-power conditions, the piezoelectric and dielectric properties obtained under small signal conditions cannot be directly applied to high-power transducers. There are three mainstream high-power characterization methods: the constant voltage method, the constant current method, and the transient method. In this study, we developed and verified a combined impedance method that integrated the advantages of the constant voltage and current methods, along with an improved transient method, for high-power testing of PZT-5H piezoelectric ceramics. The results from both methods indicated that with increasing power, the electromechanical coupling coefficient $k_{31}$ , the piezoelectric constant $d_{31}$, and the elastic compliance $s_{11}^{\mathrm{E}}$ of the PZT-5H showed increasing trends, while the mechanical quality factor $Q_{\mathrm{m}}$ first decayed rapidly and then stabilized at a fixed level. Additionally, under the combined impedance method, the temperature of the vibrators rose significantly due to self-heating, whereas the transient method generated almost no heat, and the vibrators remained at room temperature. By comparing the results from the two methods, we decoupled the effects of temperature and power on the high-power piezoelectric performance. The results showed that the self-heating temperature amplified the effects of power on $k_{31}$, $d_{31}$, and $s_{11}^{\mathrm{E}}$, while its influence on $Q_{\mathrm{m}}$ remained negligible. Full article

The effect of residual stress or heat on ferroelectrics used to convert photons into electricity was investigated. The data analysis reveals that when the PET-PZT piezoelectric transducer is UV-irradiated with a 405 nm wavelength, it becomes a photon–heat–stress electric energy converter and capacitator. Our objective was to evaluate the PET-PZT photon–heat–stress electric energy conversion performance and the role of the light’s wavelength and intensity. Converting waste energy from energy-intensive processes and systems is crucial to reducing the environmental impact and achieving net-zero emissions. To achieve these, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. Full article