Search Results (990)

This work presents the design, fabrication, and experimental characterization of microelectromechanical system (MEMS) ultrasonic transducers engineered for multi-frequency operation in photoacoustic imaging (PAI). The proposed devices integrate multiple resonant geometries, including circular diaphragms, floated crosses, anchored cross membranes, and cantilever arrays, within compact footprints to overcome the inherently narrow frequency response of conventional MEMS transducers. All devices were fabricated using the PiezoMUMPs commercial microfabrication process, with finite element simulations guiding modal optimization and laser Doppler vibrometry used for experimental validation in air. The circular diaphragm exhibited a narrowband response with a dominant resonance at 1.69 MHz and a quality factor (Q) of 268, confirming the bandwidth limitations of traditional geometries. In contrast, complex designs such as the floated cross and cantilever arrays achieved significantly broader spectral responses, with resonances spanning from 275 kHz to beyond 7.5 MHz. The cantilever array, with systematically varied arm lengths, achieved the highest modal density through asynchronous activation across the spectrum. Results demonstrate that structurally diverse MEMS devices can overcome the bandwidth constraints of traditional piezoelectric transducers. The integration of heterogeneous MEMS geometries offers a viable approach for broadband sensitivity in PAI, enabling improved spatial resolution and depth selectivity without compromising miniaturization or manufacturability. Full article

To address the issue of voice leakage during the rapid deployment of meeting rooms, a piezoelectric flexible interference structure (PFIS) for active sound masking is developed in this paper. The PFIS uses rubber as the base, allowing it to bend or fold, offering good flexibility. The PFIS generates vibration through direct contact with the target object, without the need for adhesives or installation, fulfilling the need for rapid deployment. The experiment studied the driving of PFIS under three types of interference signals, analyzing the interference performance of PFIS by combining the vibration response of the surface of the table. The results show that the vibration response generated by PFIS on the surface of the table is significantly greater than when only a human voice is present. When a 3.5 kg weight is added to the surface of PFIS, its vibration performance increases by 5.6 times. Furthermore, increasing the voltage enhances the vibration interference effect of the PFIS across the entire frequency range; after adding weight, the vibration interference performance of the PFIS is significantly improved for frequencies above 2500 Hz. It has been verified that PFIS has strong vibration interference performance, effectively masking the vibrations of objects under human voice, providing a new technical solution for information security protection in sensitive areas. Full article

Flexible and wearable pressure sensors are essential for monitoring of human motion and are distinguished by their increased sensitivity and outstanding mechanical robustness. In this study, we systematically engineered a flexible and wearable pressure sensor with a multilayer conductive architecture, arranging a sponge substrate coated in a consecutive manner with a barium zirconium titanate thin film, followed by polypyrrole, multiwalled carbon nanotubes, and eventually polydimethylsiloxane. The foundation of additional conductive pathways is enabled via the utilization of a porous framework and the hierarchical arrangement, causing the achievement of an excellent sensitivity of 9.71 kPa^–1 (0–9 kPa), a rapid 40 ms response time, and a fast 60 ms recovery period, combined with a particularly low detection limit (125 Pa) and an extended pressure range from 0 to 225 kPa. Furthermore, the integration of a rough and porous barium zirconium titanate/barium titanate thin film is expected to deliver a voltage output (1.25 V) through piezoelectric working mechanisms. This study possesses the potential to provide an innovative architecture design for advancing the development of future electronic devices for health and sports monitoring. Full article

Biofuels have emerged as a promising alternative to conventional fuels, offering improved environmental sustainability. Nevertheless, inadequate control of their physicochemical properties can lead to increased emissions and potential engine damage. Existing methods for regulating these properties depend on costly and sophisticated laboratory equipment, which poses significant challenges for integration into industrial production processes. Three-dimensional printing technology provides a cost-effective alternative to traditional fabrication methods, offering particular benefits for the development of low-cost designs for detecting liquid properties. In this work, we present a sensor system for assessing biofuel solutions. The presented device employs piezoelectric sensors integrated with 3D-printed, liquid-filled cells whose structural design is refined through experimental validation and novel optimization strategies that account for sensitivity, recovery and resolution. This system incorporates discrete electronic circuits and a microcontroller, within which artificial intelligence algorithms are implemented to correlate sensor responses with fluid viscosity and density. The proposed approach achieves calibration and resolution errors as low as 0.99% and $1.48\times {10}^{-2}$ mPa·s for viscosity, and 0.0485% and $1.9\times {10}^{-4}$ g/mL for density, enabling detection of small compositional variations in biofuels. Additionally, algorithmic methodologies for dimensionality reduction and data treatment are introduced to address temporal drift, enhance sensor lifespan and accelerate data acquisition. The resulting system is compact, precise and applicable to diverse industrial liquids. Full article

Transition metal (TM)-doped zinc oxide (ZnO) and zirconium dioxide (ZrO₂) nanocrystals exhibit complex correlations between crystal structure, defect chemistry, vibrational properties, and magnetic behavior that are strongly governed by synthesis route and dopant incorporation mechanisms. This review critically summarizes recent progress on Fe-, Mn-, and Co-doped ZnO and ZrO₂ nanocrystals synthesized by wet chemical, hydrothermal, and microwave-assisted hydrothermal methods, with emphasis on synthesis-driven phase evolution and apparent solubility limits. ZnO and ZrO₂ are treated as complementary host lattices: ZnO is a semiconducting, piezoelectric oxide with narrow solubility limits for most 3d dopants, while ZrO₂ is a dielectric, polymorphic oxide in which transition metal doping may stabilize tetragonal or cubic phases. Structural and microstructural studies using X-ray diffraction, electron microscopy, Raman spectroscopy, and Mössbauer spectroscopy demonstrate that at low dopant concentrations, TM ions may be partially incorporated into the host lattice, giving rise to diluted or defect-mediated magnetic behavior. When solubility limits are exceeded, nanoscopic secondary oxide phases emerge, leading to superparamagnetic, ferrimagnetic, or spin-glass-like responses. Magnetic measurements, including DC magnetization and AC susceptibility, reveal a continuous evolution from paramagnetism in lightly doped samples to dynamic magnetic states characteristic of nanoscale magnetic entities. Vibrational spectroscopy highlights phonon confinement, surface optical phonons, and disorder-activated modes that sensitively reflect nanocrystal size, lattice strain, and defect populations, and often correlate with magnetic dynamics. Rather than classifying these materials as diluted magnetic semiconductors, this review adopts a synthesis-driven and correlation-based framework that links dopant incorporation, local structural disorder, vibrational fingerprints, and magnetic response. By emphasizing multi-technique characterization strategies required to distinguish intrinsic from extrinsic magnetic contributions, this review provides practical guidelines for interpreting magnetism in TM-doped oxide nanocrystals and outlines implications for applications in photocatalysis, sensing, biomedicine, and electromagnetic interference (EMI) shielding. Full article

The precision drive industry has seen rapid growth, leading to an increased demand for actuators that are both highly accurate and responsive. Among these, non-resonant piezoelectric motors are particularly noteworthy. These motors are extensively employed in applications such as high-precision manufacturing, precision drug delivery, and cellular puncture, owing to their adaptable drive control and resistance to external disturbances. Given the specific requirements of these applications, it is crucial to quickly determine the relationship between the motor input parameters and output characteristics—a challenging endeavor. In this research, we examine a typical non-resonant piezoelectric motor using multiple sets of experimental data. A machine learning algorithm is employed to swiftly establish the correlation between electromechanical input parameters and output trajectory characteristics. Data are analyzed using a random forest model to understand the underlying influence mechanisms. Based on this analysis, predictions and recommendations are made to achieve optimal operating conditions for the motor. This study demonstrates that machine learning serves as an effective tool for predicting piezoelectric motor performance, facilitating rapid assessment of motor output capabilities. Full article

Z-cut lithium niobate single crystal demonstrates considerable promise for contact-based ultrasonic nondestructive testing and structural health monitoring (SHM) transducers due to its high piezoelectric coefficients, strong electromechanical coupling capability, and environmentally friendly lead-free composition. As a simulation-based theoretical exploration, this study systematically investigates the impact of gap spacing and electrode width in concentric ring configurations on the resonant characteristics and pulse-echo response of ultrasonic transducers by establishing a parametrized finite element model. Numerical simulations reveal that electrode geometry plays a critical role in determining both the effective electromechanical coupling coefficient and echo signal strength. Optimizing the electrode ring width achieved an effective electromechanical coupling coefficient ($k_{\mathit{eff}}$) of 35.2%, while systematic enlargement of the electrode gap further enhanced this value to 50.8%. The study also demonstrates that optimized ring width and adjusted electrode spacing increased the echo signal’s peak-to-peak amplitude ($V_{pp}$) by factors of 4.94 and 2.03, respectively, compared to the poorest-performing configuration within each parameter group. This study establishes that precise design of concentric electrode configurations serves as an effective strategy for tuning lithium niobate ultrasonic transducer characteristics, providing critical design guidelines for developing high-performance ultrasonic transducers for solid medium coupling. Full article

The ZnO piezoelectric coatings were deposited on the surface of 15CrMo steels by magnetron sputtering to directly excite the ultrasonic signal, effectively solving the coupling problem between the traditional probe and the pipe surface. The microstructure, mechanical properties, and ultrasonic longitudinal wave velocity of the aged samples were carried out systematically. The spheroidization grade of pearlite, evolution of carbide morphology, hardness, strength, and ultrasonic wave velocity were systematically analyzed. As the degree of aging intensifies, the material undergoes significant pearlite spheroidization and carbide coarsening. The Vickers hardness drops from 158 HV in the original state to 134.2 HV, and the yield strength and tensile strength decrease by 22.7% and 17.9%, respectively. The ultrasonic longitudinal wave velocity shows a monotonically upward trend with the increase in spheroidization grade, increasing from 5925.6 m/s in the original state to 5976 m/s at the highest spheroidization grade. Full article

Flexible piezoelectric sensors based on electrospun poly(vinylidene fluoride) (PVDF)/polyacrylonitrile (PAN)/graphene nanofibers were fabricated and evaluated for passive human body motion detection. Optimized electrospinning yielded smooth, continuous fibers with diameters of 200–250 nm and uniform films with thicknesses of 20–25 µm. Fourier transform infrared (FTIR) spectroscopy confirmed a high fraction of the piezoelectrically active β-phase in PVDF, which was further enhanced by post-deposition thermal treatment. Graphene and lithium phosphate were incorporated to improve electrical conductivity, β-phase nucleation, and piezoelectric response, while PAN provided mechanical reinforcement and flexibility. Custom test platforms were developed to simulate low-amplitude mechanical stimuli, including finger bending and pulsatile pressure. Under applied pressures of 40, 80, and 120 mmHg, the sensors generated stable millivolt-level outputs with average peak voltages of 25–30 mV, 53–60 mV, and 80–90 mV, respectively, with good repeatability and an adequate signal-to-noise ratio. These results demonstrate that PVDF/PAN/graphene nanofiber films are promising candidates for flexible, wearable piezoelectric sensors capable of detecting subtle physiological signals, and highlight the critical roles of electrospinning conditions, functional additives, and post-processing treatments in tuning their electromechanical performance. Full article

With the rapid development of high-voltage DC (HVDC) power systems, accurate measurement of surface electrostatic potential on insulating components has become critical for electric field assessment and insulation reliability. This paper proposes an electrostatic potential sensor based on cantilever micro-vibration modulation, which employs piezoelectric actuators to drive high-frequency micro-vibration of cantilever-type shielding electrodes, converting the static electrostatic potential into an alternating induced charge signal. An electrostatic induction model is established to describe the sensing principle, and the influence of structural and operating parameters on sensitivity is analyzed. Multi-physics coupled simulations are conducted to optimize the cantilever geometry and modulation frequency, aiming to enhance modulation efficiency while maintaining a compact sensor structure. To validate the effectiveness of the proposed sensor, an electrostatic potential measurement platform for insulating components is constructed, obtaining response curves of the sensor at different potentials and establishing a compensation model for the working distance correction coefficient. The experimental results demonstrate that the sensor achieves a maximum measurement error of 0.92% and a linearity of 0.47% within the 1–10 kV range. Surface potential distribution measurements of a post insulator under DC voltage agreed well with simulation results, demonstrating the effectiveness and applicability of the proposed sensor for HVDC insulation monitoring. Full article

To enhance the actuation performance of artificial muscles, a thermo-piezoelectric coupled model was developed based on the inverse piezoelectric effect of piezoelectric bimorphs. By altering the effective piezoelectric coefficient, elastic modulus, and effective thermal expansion coefficient of the thermo-piezoelectric bimorph model, the bending motion of artificial muscles was simulated. The effects of multi-walled carbon nanotube (MWCNT) and Genipin crosslinking on the bending force and output displacement of the artificial muscles were analyzed, illustrating how crosslinking affects the equivalent actuation response. The results showed that MWCNT and Genipin crosslinking significantly improved the actuation performance of the artificial muscles. Through numerical simulation, the optimal crosslinking ratio was determined to be 43.34% MWCNT and 0.1% Genipin, at which the best actuation performance was achieved. Compared to non-crosslinked techniques, the artificial muscles with crosslinked structures exhibited markedly enhanced actuation behavior. Full article

Stick–slip piezoelectric actuators are widely used in high-precision positioning systems, yet their performance is limited by backward motion during the slip stage. Although the effects of preload force, driving voltage, and driving frequency have been extensively examined, the specific influence of mover mass and its coupling with these parameters remains insufficiently understood. This study aims to clarify the mass-dependent stepping behavior of stick–slip actuators and to provide guidance for structural design. A compact stick–slip actuator incorporating a lever-type amplification mechanism is developed. Its deformation amplification capability and structural reliability are verified through motion principle analysis, finite element simulations, and modal analysis. A theoretical model is formulated to describe the inverse dependence of backward displacement on the mover mass. Systematic experiments conducted under different mover masses, preload forces, voltages, and frequencies demonstrate that the mover mass directly affects stepping displacement and interacts with input conditions to determine motion linearity and backward-slip suppression. Light movers exhibit pronounced backward motion, whereas heavier movers improve smoothness and stepping stability, although excessive mass slows the dynamic response. These results provide quantitative insight into mass-related dynamic behavior and offer practical guidelines for optimizing the performance of stick–slip actuators in precision motion control. Full article

This study comprehensively analyzes the free vibration and transient response for a sandwich piezoelectric laminated beam with elastic boundaries in a thermal environment. Quasi-3D shear deformation beam theory (Q3DBT) and Hamilton’s principle are used to obtain the thermo-electro-mechanical coupling equations, and the method of reverberation-ray matrix (MRRM) is utilized to integrate the phase and scattering relationship of the structure in a unified approach. Specifically, the scattering relationship established by the Mixed Rigid-Rod Model (MRRM) via dual coordinate systems describes the general dynamic model of the beam using generalized displacements and generalized forces at the two endpoints. This analytical solution is compared with the finite element numerical results based on Solid5 and Solid45 elements. The similarity of this approach lies in the fact that solid elements can account for the Poisson effect of thick beams, while the difference is that solid elements have a certain width; here, the error is minimized by adopting a single-element division in the width direction. Comparison of the numerical results under different geometric parameters and boundary conditions with the simulation software proves that MRRM has good accuracy and stability in analyzing the dynamic performance of sandwich piezoelectric laminated beams. On this basis, a spring-supported boundary technology is introduced to expand the flexibility of classical boundary conditions, and a detailed parameterization study is conducted on the material properties of the base layer, including the material parameters, geometric property, and the external temperature. The study in this article provides many new results for sandwich-type piezoelectric laminated structures to help further research. Full article

Self-powered sensors, leveraging their integrated energy harvesting–signal sensing capability, effectively overcome the bottlenecks of traditional sensors, including reliance on external power resources, high maintenance costs, and challenges in large-scale distributed deployment. As a result, they have become a major research focus in fields such as flexible electronics, smart healthcare, and human–machine interaction. This paper reviews the core technical paths of six major types of self-powered sensors developed in recent years, with particular emphasis on the working principles and innovative material applications associated with frictional charge transfer and electrostatic induction, pyroelectric polarization dynamics, hydrovoltaic interfacial streaming potentials, piezoelectric constitutive behavior, battery integration mechanism, and photovoltaic effect. By comparing representative achievements in fields closely related to self-powered sensors, it summarizes breakthroughs in key performance indicators such as sensitivity, detection range, response speed, cyclic stability, self-powering methods, and energy conversion efficiency. The applications discussed herein mainly cover several critical domains, including wearable medical and health monitoring systems, intelligent robotics and human–machine interaction, biomedical and implantable devices, as well as safety and ecological supervision. Finally, the current challenges facing self-powered sensors are outlined and future development directions are proposed, providing a reference for the technological iteration and industrial application of self-powered sensors. Full article

Colorectal cancer (CRC) remains a major cause of morbidity and mortality worldwide, with its incidence and biological behavior influenced by both genetic and environmental factors. Emerging evidence highlights notable sex differences in CRC, with men generally exhibiting higher incidence rates and poorer prognoses, while women often display stronger immune responses and distinct molecular profiles. Traditional screening tools, such as colonoscopy and fecal-based tests, have improved survival through early detection but are limited by invasiveness, cost, and adherence issues. In this context, biosensors have emerged as innovative diagnostic platforms capable of rapid, sensitive, and non-invasive detection of CRC-associated biomarkers, including genetic, epigenetic, and metabolic alterations. These technologies integrate biological recognition elements with nanomaterials, microfluidics, and digital systems, enabling the analysis of biomarkers such as proteins, nucleic acids, autoantibodies, epigenetic marks, and metabolic or VOC signatures from blood, stool, or breath and supporting point-of-care applications. Electrochemical, optical, piezoelectric, and FET platforms enable label-free or ultrasensitive multiplexed readouts and align with liquid biopsy workflows. Despite challenges related to standardization, robustness in complex matrices, and clinical validation, advances in nanotechnology, multi-analyte biosensing with artificial intelligence are enhancing biosensor performance. Integrating biosensor-based diagnostics with knowledge of sex-specific molecular and hormonal pathways may lead to more precise and equitable approaches in CRC detection, selection of therapeutic regimes and management. Full article