Ceramic Transducers Research Articles

The Orientation Dependence of the Fingerprint Effect for Slip Speed Estimation and Control

The phenomenon through which vibrations are produced with frequencies related to the period of fingerprint ridges and the speed they slide across a surface is known as the fingerprint effect. Here, we use a simple bioinspired sensor with parallel, straight, fingerprint-like ridges and a single ferroelectric ceramic transducer to show that the fingerprint effect is orientation dependent and that, if the orientation is known, it can be used to estimate slip speed. Our results, obtained at sliding speeds of 15, 20, and 25 mm/s and orientations from 0° to 90°, clearly demonstrate this dependence. We then describe a simple algorithm for estimating slip speed in real time. Using experimental results as input, we use that algorithm to run simulations, using MATLAB software, of real-time slip speed estimation. From these simulations, we identify some tradeoffs in parameter selection for the slip speed estimation algorithm. Finally, the fingerprint effect is used for real-time slip speed estimation for feedback in a controlled slip experiment.

Energy harvesting and storage with ceramic piezoelectric transducers coupled with an ionic liquid-based supercapacitor

One of the main issues of wearable electronic devices regards their power supply and autonomy. The exploitation of mechanical energy from body motion and vibrations can be realized by using piezoelectric materials coupled with a proper energy storage device. To this aim, Self-Powered Supercapacitors (SPSCs) have been investigated over the last decades, either as internally integrated SPSC (iSPSC), where the piezoelectric element of the device is used as Super Capacitor (SC) separator, or via an external integration (eSPSC), where the piezoelectric unit and the SC are connected by a bridge rectifier. In this paper, an eSPSC power supply is developed by integrating a stuck of commercial ceramic piezoelectric disks and an ionic liquid-based micro-SC. In detail, a stack of 15 commercial lead zirconate titanate (PZT) disks is used as the energy harvesting unit and mechanically stressed by a compressive force of 85 N at 2 Hz. The piezoelectric output successfully charged the 22 mF supercapacitor up to 3.1 V after 2 h of test, achieving a stored energy value equal to 110 mJ. The proposed integrated system outperforms the state-of-the-art SPSC assembled with micro-SC (both iSPSC and eSPSC). The use of the two different units (piezo-energy harvesting unit and micro-SC energy storage unit) allows an independent sizing and tuning of the supercapacitor according to the output current of the piezoelectric unit.

An Impact Localization Solution Using Embedded Intelligence-Methodology and Experimental Verification via a Resource-Constrained IoT Device.

Recent advances both in hardware and software have facilitated the embedded intelligence (EI) research field, and enabled machine learning and decision-making integration in resource-scarce IoT devices and systems, realizing "conscious" and self-explanatory objects (smart objects). In the context of the broad use of WSNs in advanced IoT applications, this is the first work to provide an extreme-edge system, to address structural health monitoring (SHM) on polymethyl methacrylate (PPMA) thin-plate. To the best of our knowledge, state-of-the-art solutions primarily utilize impact positioning methods based on the time of arrival of the stress wave, while in the last decade machine learning data analysis has been performed, by more expensive and resource-abundant equipment than general/development purpose IoT devices, both for the collection and the inference stages of the monitoring system. In contrast to the existing systems, we propose a methodology and a system, implemented by a low-cost device, with the benefit of performing an online and on-device impact localization service from an agnostic perspective, regarding the material and the sensors' location (as none of those attributes are used). Thus, a design of experiments and the corresponding methodology to build an experimental time-series dataset for impact detection and localization is proposed, using ceramic piezoelectric transducers (PZTs). The system is excited with a steel ball, varying the height from which it is released. Based on TinyML technology for embedding intelligence in low-power devices, we implement and validate random forest and shallow neural network models to localize in real-time (less than 400 ms latency) any occurring impacts on the structure, achieving higher than 90% accuracy.

Large-scale piezoelectric ultrasonic transducers with tubular near-period phononic crystal point defect structure

<sec>The coupling vibration of large-scale piezoelectric ultrasonic transducer will make the average value of the longitudinal displacement amplitude of its radiation surface small and the amplitude distribution uneven, which seriously affects the performance and reliability of the system. In order to improve the performance of large-scale ultrasonic vibration system, a two-dimensional hole/slot near-periodic phononic crystal structure is used to suppress the transverse vibration, but the structure will in turn affect the mechanical strength of the transducer while achieving the suppression of the transverse vibration. The working bandwidth and other performance parameters have adverse effects. Based on this, a new idea of optimizing the large-scale sandwich longitudinal vibration piezoelectric ceramic transducer by using the tubular near-periodic phononic crystal point defect structure is proposed. This method can not only use the point defect mode of the constructed solid/gas two-dimensional near-periodic phononic crystal structure to obtain extremely low energy loss, but also effectively improve the longitudinal displacement amplitude and amplitude distribution uniformity of the radiation surface of the system. The double annular holes in the pipe string structure can also be used to enhance the multiple scattering of sound waves, so that the transducer can also produce a band gap under the low conditions of the pipe string, effectively suppressing the transverse vibration, at the same time, significantly broadening the working bandwidth of the transducer system, enhancing the stability and mechanical strength of the system, and reducing the processing cost. Simulation results and experimental processing test results also prove the effectiveness of the optimization.</sec><sec>In order to find the best parameters for the performance of the large-scale longitudinal vibration piezoelectric ultrasonic transducer, in the paper the finite element analysis software is used to study the influence of the inner radius <i>r</i><sub>1</sub> of the pipe string, the width <i>r</i> of the pipe string ring, the radius <i>R</i> of the outermost air cylinder hole, and the height <i>h</i><sub>2</sub> of the pipe string at the longitudinal resonance frequency of the transducer performance, the longitudinal displacement amplitude distribution uniformity of the radiation surface, and the average longitudinal displacement amplitude. In the research is finally found the range of parameters that can make the performance of the transducer reach a relatively ideal state. The simulation results show that the tubular near-periodic phononic crystal point defect structure can improve the performance of large-scale longitudinal vibration piezoelectric ultrasonic transducer.</sec>

A self-powered wearable seizure-monitoring/brain-stimulating system for potential epilepsy treatment

A new self-powered wearable body-detecting/brain-stimulating system for monitoring and restraining epilepsy has been fabricated. The system can monitor body motion in real time and transmit the stimulus signals to brain for restraining the epileptic seizures. The system is composed of energy harvesting module, the body motion detection sensor, the data processing center, and neural stimulator. An arch-shaped device made of piezoelectric ceramic transducer (lead zirconate titanate; PZT) as energy harvesting module can convert the mechanical energy generated by body movement into electricity power. The motion detection sensor is made of polyvinylidene fluoride (PVDF) doped with zinc oxide (ZnO) nanostructures, which can detect the tiny movements of the human body and transmit sensing signals to the data processing center. The data processing center can determine the epileptic seizure and generate neural stimulating signals. By stimulating the dentate gyrus/hilus brain region of mice, the total duration of epileptic seizures in mice is significantly reduced by 40–50%. This new self-powered strategy demonstrates the potential of brain-machine-interface system for personalized treatment of brain disease.

Study of wavelength-switchable watt-level blue external cavity diode laser for NO2 S-DIAL

A 2.3 W wavelength-switchable blue external cavity diode laser (ECDL) was studied. The laser was built on Littrow configuration and a piezoelectric ceramic transducer (PZT) driver was employed to change the Littrow angle for wavelength tuning. Its emitting wavelength can be switched between 447.46 nm and 448.10 nm which are the required wavelengths for NO2 differential absorption lidar application. The measured spectral linewidth of the proposed ECDL was 0.08 nm. The main peak was at least 35 dB stronger than its adjacent freely running emission peak and background amplified spontaneous emission (ASE). The wavelength switching dynamics were inspected and shows good repeatability at frequencies of 16.7 Hz and 50 Hz.

Optimization of a sandwich longitudinal vibration transducer with a large radiation surface based on hole structure of near-periodic phononic crystal

<p indent="0mm">The existence of radial vibration in a large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer will reduce the longitudinal radiated sound power and shorten the service life of the transducer, which seriously affects its performance and reliability. To reduce the strong coupling between longitudinal and radial vibration, ensure high longitudinal working efficiency and reliability, and overcome the disadvantages of narrow working bandwidth, poor uniformity of amplitude distribution, and small displacement amplitude, the large-dimension sandwich longitudinal vibration piezoelectric ceramic transducer is optimized through machining several periodic holes on the front cover plate of the transducer to form a multi-point deformation defect structure. In this study, the simulation software is used to simulate and analyze the performance index of the optimized transducer, and the optimization effect is verified through experiments. The results show that the large-dimension piezoelectric ceramic transducer based on a multi-point deformation defect near-periodic phononic crystal structure has a single longitudinal vibration mode, which can effectively improve the displacement amplitude and amplitude distribution uniformity of the radiation surface of a large-dimension transducer and broaden the transducer’s working bandwidth.

Research on Inherent Frequency and Vibration Characteristics of Sandwich Piezoelectric Ceramic Transducer

Great progress has been made in the field of ultrasonic processing in recent years, and piezoelectric ceramic transducers have been widely used as drive sources. In this paper, a sandwich piezoelectric ceramic transducer is designed, and the vibration of each part of the transducer is analyzed by elastic mechanics and piezoelectric theory. According to its mechanical and electrical boundary conditions, the vibration model of the piezoelectric transducer was established. Based on the equivalent elastic modulus method for simplifying the pre-stressed bolts into a one-dimensional transducer vibration model, the relationship between the one-dimensional axial response frequency of the transducer and the length of each component was obtained. Based on the half wavelength theory, a transducer with the vibration node in the crystal stack and an inherent frequency of 15 kHz was designed and fabricated. In order to verify the natural frequency and vibration characteristics of the piezoelectric transducer, a laser vibration measurement system was built in this study. The vibration characteristics of the transducer under different parameters such as voltage and frequency were analyzed, and the accuracy of the vibration model was verified. The vibration states of the end surface of the transducer and the radial surface were evaluated at the first-order inherent frequency and second-order inherent frequency. The results show that the equivalent simplified model established in this study can effectively design the inherent frequency of the transducer, and the operation at the first-order inherent frequency meets the one-dimensional assumptions of this study. The transducer operating conditions measured in this study also provide a more detailed reference for ultrasonic processing applications.

A probe-based nanometric morphology measurement system using intermittent-contact mode.

In the present study, a homemade probe-based nanometric morphology measurement system is proposed, which can be easily integrated with other probes, such as a diamond probe and an electrochemical electrode. In this system, an intermittent-contact mode is adopted, which is based on a set of micro-force servo modules. The micro-force serve module is mainly composed of a piezoelectric ceramic transducer, a capacitive displacement sensor, an excitation piezoelectric ceramic ring, and a four-beam spring. The four-beam spring integrated with a diamond probe is driven by the excitation piezoelectric ceramic ring. The mechanical structure and the control system of the measurement system are also designed. The vibration amplitude and the resolution of a normal load are calibrated during the engagement process under open-loop control. Moreover, the optimal values for parameters P, I, and D are obtained for the closed-loop measurement. The performance of the developed system is verified by measuring a standard sample. The measured depths agree well with the results obtained by commercial atomic force microscopy. The developed system can be used to measure nanostructures with high precision.

Research and Experimental Verification of a Flextensional Disk Transducer Based on Relaxor Ferroelectric Single Crystals

In this article, the electroacoustic properties of the flextensional disk transducer based on relaxor ferroelectric single crystals are studied. First, the transducer structure, consisting of relaxor ferroelectric single crystals, metal plates, and air cavity, and an operating principle are introduced. Then, we investigate, by finite element modeling, the influence of different air cavity sizes on the transducer behavior. Furthermore, we optimize the size of the air cavity and analyze the performance of flextensional disk transducers based on relaxor ferroelectric single crystals and piezoelectric ceramics, such as the resonant frequency and transmitting voltage response (TVR). Finally, transducers of the same size are manufactured using the two kinds of materials, and the experimental measurements are carried out in an anechoic water tank. The measured maximum TVR of the single-crystal transducer is 141.04 dB at 22.2 kHz. Compared with the piezoelectric ceramic transducer, the maximum TVR of the single-crystal transducer is increased by 12.51 dB, and the corresponding resonant frequency is reduced by 4.8 kHz, which extends the working frequency.

Design and experimental study of a rotational piezoelectric energy harvester

This article presents the characterization of an rotational generator with ceramic piezoelectric transducers, applied to energy harvesting. The physical structure developed, presents flexibility in relation to the number of beams, piezoelectric elements and coupling of generator modules, and keeps the piezoelectric transducers without direct contact with extern environment, which allows the device adaptation for practical applications. The prototype developed has two generator modules, totaling four beams with two piezoelectric transducers PZT C-64 each, and it worked for approximately 670 hours, without waste signs. An experimental configuration was developed to analyze the behavior of the proposed generator, with the generator being driven by a motor coupled to its axis with a rotation speed of 1 Hz to 35 Hz. The signals generated by the beans were connected to variable resistors, obtaining different power values in each one of the blades, justified by the manual manufacturing process. The results showed that the suggested harvester has high durability and the potential to power wireless sensors that are integrated into rotating machines.

Ultrabroad-bandwidth ultrasonic transducer based on Sm-doped PMN-PT ceramic/epoxy 1–3 composite

Ultrasonic transducers for nondestructive testing (NDT) require wide bandwidth and high sensitivity to obtain good axial resolution and strong signal reception, which requires active materials with high electromechanical coupling performance. In this work, 2.5 mol% Sm-doped Pb(Mg1/3Nb2/3)O3-30PbTiO3 (PMN-30PT:2.5Sm) piezoelectric ceramics with excellent piezoelectric properties (d33 =1065 pC/N, and k33 = 77 %) were synthesized and a ceramic/epoxy 1–3 composite ultrasonic transducer was fabricated. The center frequency is around 2.3 MHz, the − 6 dB bandwidth reaches 135.9 %, and the insertion loss is −18.7 dB. Compared with the transducer made of PZT-5H composite, the −6 dB bandwidth is increased by 45.3 % and the insertion loss is increased by 2.2 dB. The imaging experiments also show that the PMN-30PT:2.5Sm ceramic transducer has a better axial resolution (at −6 dB).

An intelligent barrier using ultrasonic technology

Abstract The article is devoted to the complete design of an intelligent barrier that uses piezoelectric ceramic transducers as transmitter of an acoustic signal and as a receiver. There is a relatively rich device base on the market for these transducers. These transducers are also not economically demanding. The barrier is composed of three identical bars. A continues wave rectangular signal generation is used for excitation of the converters on the transmitting side. The receiving side is more complex. A signal from the receiving transducer is first analog pre-processed and converted to logical values of 0 or 1. Subsequently, these signals are processed in a microcontroller system, evaluated and a possible alarm of a presence of an intruder is signaled using a display, a light-emitting diode and a piezoelectric siren. The display also shows the number of alarms. Some intelligence is added to the system by classifying a potential intruder. The functionality of the system is verified in a detail and discussed.

ZnO/NiO heterostructure-based microsensors used in formaldehyde detection at room temperature: Influence of the sensor operating voltage.

Recently the emissions of volatile organic compounds (VOCs) in the atmosphere have increased dramatically with rapid development of urbanization and industry. This led to a large decline in air quality around the world, which resulted in a heavy impact on human health. Therefore, new/cheap detection devices for VOCs are of high interest. Formaldehyde (FA) is a very toxic VOC, which damages the respiratory system even in the smallest doses and short exposure time. Zinc oxide (ZnO)/nickel oxide (NiO) heterostructures were synthesized using an economical route: firstly, NiO was prepared by liquid exfoliation technique and deposited by dip-coating on alumina ceramic transducers with two interdigital gold (Au) electrodes, followed by low—temperature hydrothermal growth of ZnO. The as-prepared sensors were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM-EDAX), and X-Ray fluorescence (XRF). The response/recovery of ZnO/NiO heterostructure-based microsensors for formaldehyde was investigated at room temperature, in agreement with modern sensing requirements. The sensor operating voltage was varied between 1.5 and 5.0 V direct current (DC), to achieve the best sensor performance.

Piezoelectric transducer comparison for vibrational motion energy harvesting

Mechanical waste energy can be used to generate naturally responsive power. Vibration is a frequent type of mechanical energy source. This work describes the use of unimorph, bimorph, and ceramic disc piezoelectric transducers to capture vibrational motion energy to fulfil the energy requirements of mobile electronic gadgets. The piezoelectric transducer is one of the most widely utilised mechanisms for vibration energy collecting due to its design versatility. The ability to collect vibration energy from motorcycle engines was conceptually and experimentally assessed on different motorcycle engine speeds, frequency and comparable time length, acceleration, and output voltages. The study’s goal was to empirically confirm the idea that bimorph piezoelectric transducers outperform unimorph and ceramic disc piezoelectric transducers. We also show that increased motor speeds and varied frequencies provided to the output voltage production.

Performance enhancement of ultrasonic transducer made of textured PNN-PZT ceramic

In this paper, 0.36Pb(Ni[Formula: see text]Nb[Formula: see text])O3–0.24PbZrO3–0.40PbTiO3(PNN-PZT) ceramic was prepared, and texture engineering was performed on this PNN-PZT ceramic to improve its electromechanical properties and temperature stability. Single element ultrasonic transducers were prepared using PNN-PZT, PNN-PZT textured ceramics, and their performance were evaluated and compared using a PZT-5H ceramic based transducer as the benchmark. It is shown that the sensitivity and bandwidth of the PNN-PZT textured ceramic-based transducer are much superior to regular PNN-PZT ceramic and PZT-5H ceramic based transducers.

Lamb waves-based technologies for structural health monitoring of composite structures for aircraft applications

The most common researched area of damage in a composite material such as carbon fibre reinforced plastics (CFRP) used currently in aircraft construction is barely visible impact damage (BVID), significantly reducing mechanical properties. Early detection and qualification would improve safety and reduce the cost of repair. In this context, structural health monitoring (SHM) techniques have been developed that could monitor a structure at any time by using a network of sensors. Widely used discrete ceramic transducers can generate and sense Lamb waves travelling in the structure. Wave propagation must then be analysed for effective damage identification. An effective SHM system is desired to meet several demands, such as minimised weight penalty, non-intrusive system not interfering with the structure performance, cost-effectiveness for implementation with targeted sensitivity and area coverage, capability of monitoring non-accessible and critical hot spot regions, robustness, and reliability. This review starts with an introduction on Lamb waves fundamentals and their use in SHM, and then particularly focuses on methods using piezoelectric transducers and mode selection. Some relevant applications on different structural configurations are discussed. Finally, recent developments on piezoelectric coating and direct-write sensor technology for tailored transducers are highlighted with some thoughts for near future research work.

Optical high repetition rate stabilization based an all-polarization-maintaining figure-of-nine Er-fiber laser

Optical frequency comb (OFC) based on mode-locked fiber lasers has abstracted extensive interest in the field of laser ranging and precision spectroscopy with its extremely high time–frequency accuracy. Therefore, the repetition rate stabilization plays a notably key role in OFC. Mechanical motion is generally used to change the geometric length of the laser cavity to stabilize the repetition rate. However, this method has some disadvantages such as high feedback voltage and mechanical disturbance caused by the characteristics of the piezoelectric ceramic transducer (PZT). To overcome these problems, the refractive index of the gain fiber can be regulated via controlling the pump power, thereby optically stabilizing the repetition rate. In this study, we reported the optical repetition rate stabilization via regulating the nonlinear refractive index of Er-fiber in an all-polarization-maintaining (PM) figure-of-nine laser cavity. The repetition rate reached 80.1 MHz and was stabilized for more than 1 h. The standard deviation (SD) was 178 μHz within 1-s gate time. As far as we know, in terms of optical repetition rate stabilization, the mode-locked Er-fiber laser achieved the highest repetition rate.

Coupling Effects of Crosstalk and Parasitic Loss on Capacitive Micromachined Ultrasonic Transducers

Capacitive micromachined ultrasonic transducers (CMUTs) have been widely utilized in applications of biomolecule monitoring, ultrasound medical diagnosis, and ultrasound therapy because of their advantages in high-level integration with integrated circuits, good impedance matching for acoustic transmission, and flexible element and array configuration compared with conventional piezoelectric ceramic transducers. Crosstalk effects on dynamics of a CMUT element, <i>i.e.</i> electrical, mechanical, and acoustic performance, would lead to unexpected spurious resonances. In this study, the mutual interaction from fluid and nearby cells in a CMUT element is newly investigated specially aiming to characterize their coupling effects with series and parallel parasitic effects based on a nonlinear Equivalent Circuit Model (ECM). The mutual interaction is evaluated with the electromechanical and acoustic characteristics by comparison between ECM and 3D Finite Element Analysis (FEA). Two representative CMUT element configurations, that are the rectangular with nine cells and the hexagonal with seven cells, are analyzed with different center-to-center distance. The radii of cells are set to be <inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula>/8 with different edge-to-edge distances. The parasitic effects are modeled by a series parasitic factor and a parallel-capacitance parasitic ratio. The coupling influence of crosstalk and parasitic effects on the performance of a CMUT element is evaluated, such as the impedance, phase, conductance, velocity, and ultrasound pressure field. The results of ECM-FEA-based methods show good agreements, and the improved ECM can be used for co-parasitic extraction with front-end interface.

Effects of radial stress on piezoelectric ceramic tubes and transducers.

Static analysis is performed for fiber windings to quantitatively control the radial stress at the outer radius of the piezoelectric ceramic tube. The radial stress is verified both experimentally and theoretically, and the dependence of the resonant and material properties of the piezoelectric ceramic tubes on the radial stress is clarified. The resonance frequencies and dielectric loss remain relatively stable, but the relative permittivity and the short circuit elastic constant decrease with the radial stress. The variations of the increased bandwidth and decreased electromechanical coupling coefficient (k31), piezoelectric constant (d31 and g31), and mechanical quality factor (Qm) are associated with the height-to-radius ratio. The properties of three cylindrical transducers applied with various radial stress show similar change tendencies, and a difference of 0.34 MPa radial stress results in a variation of approximately 13 in the bandwidth, 14 in Qm, 15 in k31, d31, and g31, and 16 in the amplitude of the first pulse. These results suggest that the consistency of the radial stress is essential, and it should be relatively small. These findings guide the design and preparation of the enhanced transducer.