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Piezoelectric materials with shunt circuits have aroused much research interest due to flexible parameter adjustment. However, shunted piezoelectric elements are difficult to respond to the dynamic changes in the whole system due to the absence of autonomous control ability, which constrains their practical applications. Here, we propose a digital metalayer to control the wave energy transmission across different materials in real time. This digital metalayer comprises a stack of multiple piezoelectric lead zirconate titanate (PZT) disks connected with shunt capacitance circuits (SCCs). The external digital control system adjusts the effective acoustic impedance of the PZT disks through digital potentiometers and microprogrammed control unit, thereby enabling digital manipulation of wave transmission. Utilization of optimized SCCs further enhances adjustment accuracy, supporting both negative and positive capacitance values. The experiments demonstrate that this digital metalayer exhibits remarkable performance in controlling wave transmission. Moreover, the distinct variations in transmitted amplitudes, precisely controlled by the digital metalayer, are harnessed as binary signals for information transmission. An image of letters is encoded into a series of amplitude-modulated waves by the digital metalayer and clearly transmitted. The proposed digital metalayer shows great promise for applications in intelligent impedance matching and the real-time modulation systems. [ABSTRACT FROM AUTHOR]

Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers. [ABSTRACT FROM AUTHOR]

Investigation and implementation of Active Willis Metamaterials (AWM) have been done exclusively, in all the available literature, by approaches that do not rely on any solid control theory basis. When coupled with piezoelectric control elements, the available approaches have not included, from the first principles, the exact form of the constitutive relationship of the piezoelectric materials. Furthermore, in all these approaches, stability analysis, robustness, ability to accommodate uncertainty or parameter changes, or consideration of disturbance rejection has not been addressed at all. More importantly, the available formulations have always mixed the flow and effort variables of the AWM, resulting in a form that is totally incompatible for the use in generating, investigating, or even designing any appropriate sensing or control applications of the material. In this paper, the piezoelectric-based AWM is modeled, from the first principles, to develop a constitutive coupling form that enables its use in actuation, sensing, and as an integrated controller that can be analyzed, designed, and optimized using the classical, optimal, and robust control system theories. Lagrange dynamics formulation is used to generate the equations governing the Willis coupling, the piezoelectric coupling, as well as the active robust controller. With this developed controlled-based structure of the AWM, the inherent and powerful capabilities of the AWM that lie in its ability to robustly control the material properties themselves such as the compliance (or stiffness) and specific volume (or density) are demonstrated in great detail via several numerical examples. Controlling these properties enables the AWM to be used in numerous important and imaginative applications such as cloaking, beam shifting, beam focusing, as well as many other applications that are limited only by our imagination. [ABSTRACT FROM AUTHOR]

The increasing demands of device applications in harsh environments have led to higher expectations for temperature and pressure resistance in high-temperature piezoelectric materials. In order to understand the performance characteristics of BiScO3-PbTiO3 (BS-PT) high-temperature piezoelectric materials in practical device applications, this study focuses on analyzing the dielectric, piezoelectric, and ferroelectric properties of BS-64PT ceramics under uniaxial stress up to 150 MPa, as well as its electromechanical performance under a hydrostatic pressure of up to 400 MPa. As the uniaxial pressure increases, both the bias-field and large-signal piezoelectric coefficients exhibit a pattern of initially increasing and subsequently decreasing. Furthermore, the bias-field piezoelectric coefficient exceeds 450 pC/N and the large-signal piezoelectric coefficient surpasses 630 pC/N under uniaxial pressures below 100 MPa. This highlights their exceptional resistance to depolarization caused by uniaxial stress. To obtain more precise piezoelectric properties for BS-64PT ceramics in the 31 and 33 modes under hydrostatic pressure, the admittance fitting method was utilized. This method takes into account the significant losses at higher pressures. Within the pressure range of 0–400 MPa, the values of d33 and d31 for BS-64PT ceramics exhibited a minor change of 7.6% and 8%, respectively. These findings indicate that BS-64PT ceramics exhibit more stable piezoelectric properties under both uniaxial and hydrostatic pressures when compared to the majority of Pb-based perovskite-structured materials. The exceptional stability of piezoelectric properties in BS-PT ceramics can be primarily attributed to their elevated anisotropy energy or coercivity field compared to other perovskite-structured Pb(Mg1/3Nb2/3)O3 (PMN) / Pb(Zr,Ti)O3 (PZT)-based ceramics reported. [ABSTRACT FROM AUTHOR]

In this paper, a new Stroh formalism for gradient electro-mechanics is derived for the first time, which is both mathematically concise and numerically powerful, applicable to generally coupled anisotropic material systems. Based on this new formalism, the complicated Lamb wave in flexoelectric and piezoelectric plates is investigated. The dispersion equation is obtained by solving the eigenvalue problem along with the unconditionally stable dual-variable and position method. From the obtained dispersion equation, the dispersion curves and mode shapes of the Lamb wave are calculated by the 1D form of the multidimensional moduli ratio convergence method. Two important and interesting features are observed from our analysis: One is the difference in the mode shape symmetry between the piezoelectric and flexoelectric cases, and the other is the size-dependent property of the flexoelectric effect as observed by nondimensionalization. These features are further illustrated by comparing the dispersion curves and wave-mode shapes among the three different material models (purely piezoelectric, purely flexoelectric, and flexoelectric and piezoelectric coupled). The newly derived Stroh formalism offers a robust, concise, and unified approach for dealing with strain gradient electro-mechanic materials with crystal systems of general anisotropy. The present work also explains the physical mechanism of symmetry breaking observed, as induced by flexoelectric coupling in piezoelectric materials. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) piezoelectric nanomaterials have widely been studied recently due to their promise for various applications in technology. Investigation of vertical piezoelectricity will contribute to a deeper understanding of the intrinsic mechanism of piezoelectric effects in the 2D structures. In this paper, we report a first-principle study for the structural, electronic, piezoelectric, and transport properties of new-designed Janus WSi Z 3 H (Z = N, P, and As) monolayers. The structural stability of WSi Z 3 H is theoretically confirmed based on the energetic, phonon dispersion, and also elastic analyses. At the ground state, while WSiN 3 H is an indirect semiconductor, both WSiP 3 H and WSiAs 3 H are predicted to be direct semiconductors with smaller bandgaps. When the spin-orbit coupling effects are taken into account, a large valley spin splitting is observed at the K point of WSi Z 3 H materials. Interestingly, a giant Rashba spin splitting is found in WSiP 3 H and WSiAs 3 H with Rashba constant α R up to 770.91 meV Å. Additionally, our first-principles study indicates that Janus WSi Z 3 H monolayers are piezoelectric semiconductors with high out-of-plane piezoelectric coefficient | d 31 | , up to 0.15 pm/V, due to the broken mirror symmetry. Besides, with high electron mobilities and also possessing direct band gaps, WSiP 3 H and WSiAs 3 H monolayers are favorable for applications in optoelectronics. [ABSTRACT FROM AUTHOR]

Piezoresponse Force Microscopy (PFM) is capable of detecting strains in piezoelectric materials down to the picometer range. Driven by diverse application areas, numerous weaker electromechanical materials have emerged. The smaller signals associated with them have uncovered ubiquitous crosstalk challenges that limit the accuracy of measurements and that can even mask them entirely. Previously, using an interferometric displacement sensor (IDS), we demonstrated the existence of a special spot position immediately above the tip of the cantilever, where the signal due to body-electrostatic (BES) forces is nullified. Placing the IDS detection spot at this location allows sensitive and BES artifact-free electromechanical measurements. We denote this position as x I D S / L = 1 , where x I D S is the spot position along the cantilever and L is the distance between the base and tip. Recently, a similar approach has been proposed for BES nullification for the more commonly used optical beam deflection (OBD) technique, with a different null position at x O B D / L ≈ 0.6 . In the present study, a large number of automated, sub-resonance spot position dependent measurements were conducted on periodically poled lithium niobate. In this work, both IDS and OBD responses were measured simultaneously, allowing direct comparisons of the two approaches. In these extensive measurements, for the IDS, we routinely observed x I D S / L ≈ 1 . In contrast, the OBD null position ranged over a significant fraction of the cantilever length. Worryingly, the magnitudes of the amplitudes measured at the respective null positions were typically different, often by as much as 100%. Theoretically, we explain these results by invoking the presence of both BES and in-plane forces electromechanical forces acting on the tip using an Euler–Bernoulli cantilever beam model. Notably, the IDS measurements support the electromechanical response of lithium niobate predicted with a rigorous electro-elastic model of a sharp PFM tip in the strong indentation contact limit [ d e f f ≈ 12 pm / V , Kalinin et al., Phys. Rev. B 70, 184101 (2004)]. [ABSTRACT FROM AUTHOR]

This article proposes a new formulation of Fourier's heat conduction law by considering the size effect of functionally graded piezoelectric materials. Which contains the Caputo–Fabrizio type fractional-order heat transfer equation. The Kelvin–Voigt model was used to characterize the viscoelastic behavior of the material. The model is applied to the study of the thermodynamic behavior of functionally graded piezoelectric rods under thermal shock. It is assumed that the ends of the functionally graded piezoelectric rod are fixed and insulated, that there is no electric potential between the ends, and that the physical properties of the rod vary exponentially along the axial direction of the rod. The control equation is solved by the Laplace integral transformation and its numerical inverse transformation, and the distribution of the studied physics field is obtained, which is illustrated graphically. Finally, the effects of nonhomogeneity index, fractional-order derivatives, nonlocal parameters, and viscoelastic coefficients on the characteristics of the physical variables are investigated and discussed. [ABSTRACT FROM AUTHOR]

Although technologies and processes for creating smart composite structures have been established, significant limitations still necessitate additional research to overcome. Indeed, numerous studies have highlighted the challenges of embedding active elements, often leading to compromises in the structural integrity of smart composite materials. In contrast, this study introduces a novel perspective, offering innovative insights and valuable contributions to the existing knowledge. The primary contribution of this study lies in addressing the critical need for the seamless integration of active materials within composite structures. To demonstrate this, our study considers the potential integration of Polyvinylidene Fluoride (PVDF), a polymer-based piezoelectric material, with pre-impregnated unidirectional flax fibers to produce a smart composite structure. The consolidation molding process was adopted to manufacture the smart composite samples for investigations. Experimental analysis were then considered to evaluate the influence of the embedded PVDF film on the mechanical performance of the structure and to assess the resulting functional properties. X-ray micro-computed tomography and an additional strength-of-material test approach, Interlaminar Shear Strength (ILSS), were performed to explore the impact of the insertion on the integrity of the laminate structure. On the other hand, we conducted vibration tests to assess the electromechanical properties. The tomography results reveal void elimination in the edges of the active material insert, which could be attributed to the choice of thin film materials. Moreover, the ILSS results highlight the minimal impact of PVDF material on mechanical performance, showcasing a mere 0.69% degradation of the material strength. These results are comparable to the recently reported works but with an appreciable margin of improvement. The vibration test response demonstrates the ability of the embedded piezoelectric material to generate voltage, which validates our integration procedure. The smart composite material's sensitivity to ambient vibrations and its power generation potential show promise for sensing and energy harvesting. [ABSTRACT FROM AUTHOR]

Increased consumption of non-renewable energy sources, such as batteries, have led to increased environmental pollution and critical energy crises. Harvesting energy from vibration sources, using piezoelectric cantilevers, may be one of the main solutions to extending the life of the battery of some autonomous devices and either reducing or eliminating the need to replace them in service. This would make sensors self-powered, for instance. To minimize the volume of the Energy Harvester, a configuration with a circular frame supporting a radial set of bimorph piezoelectric beams with a proof mass at the tip is proposed. An analytic model is first developed to investigate the behavior of the electromechanical coupling, preliminarily sizing the design parameters, and to estimate the maximum power converted. A numerical model is then developed, in the COMSOL® Multiphysics software, to analyze all of the system details. Some FEM analyses allow for verifying the accuracy of the analytic model and predicting the dynamic system behavior under different load conditions. A critical issue in properly predicting the performance of such device is the electric circuit which is coupled to extract the charge produced. Therefore, the design of this read-out circuit is herein addressed. The LTspice XVII® software is then used to model the charge readout circuit. The electronic components interconnected within the circuit are first determined, and their electrical dynamic behavior is studied when coupled with the mechanical system. The efficiency of charge production and energy storage is evaluated by integrating the whole electromechanical system, including the readout circuit with the numerical model. The performance looks compatible with the required values proposed for some practical industrial applications, being also described. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of structural optimization for the piezoelectric energy harvesters by summarizing the characteristics, working principles, advantages, disadvantages, performance, evaluation factors, and potential applications of each amplifier structure. This includes the cantilever, flexure structure, combined structure, multistage structure, and derivative designs such as compound and hinge designs. Examples and optimization method of structural design which utilizes the compressive mode, 33-mode configuration, and stacking design of piezoelectric material is provided. The power output, amplification ratio, and the applied mechanism theory of each structure are then compared and discussed to ease the benchmarking process for future research. HIGHLIGHTS: Mechanical amplifier frames relevant to piezoelectric transducer are reviewed. Summarized previous work on design characteristics, applications, pros, and cons. Figure of merit with power density and amplification factor is presented. Design trends and guidance are provided for future research. [ABSTRACT FROM AUTHOR]

To improve the application depth and breadth of intelligent unit devices made from piezoelectric structures, their kinetic properties shall be urgently studied. Herein, based on the basic equations and boundary conditions of piezoelectric materials, an interpolation coverage function of node displacement was introduced into the displacement shape function and potential shape function of coupling electromechanical finite element method (FEM), forming an electromechanical coupling enriched FEM generalized shape function. Together with the variation principle, an electromechanical coupling enriched FEM was put forward, and its motion equations were deduced. Next, the free vibration and transient response of the piezoelectric structure were analyzed, and the accuracy and validity of the new method were validated with numerical cases. Results show this method has high application prospects for analyzing the dynamic properties of piezoelectric material structures. [ABSTRACT FROM AUTHOR]

High-frequency ultrasound plays a vital role in ultrasonic imaging and particle manipulation. However, the control of high-frequency ultrasound fields with traditional acoustic lens presents challenges in impedance matching, precise control, material selection. Therefore, piezoelectric ultrasonic transducers prepared based on traditional methods are difficult to achieve high frequency and efficient sound beam control. To address these challenges, we have developed a piezoelectric metasurface-based ultrasonic transducer, using the encode binary information method to modulate acoustic waves. Simulation results reveal that at a frequency of 50 MHz, the system exhibits efficient acoustic focusing capabilities, which have been successfully applied in the experimental trapping of microspheres with acoustic tweezers. The design and development of high-frequency ultrasound transducers have emerged as a burgeoning research area at the confluence of acoustics and numerous interdisciplinary fields. [ABSTRACT FROM AUTHOR]

Advanced ferroelectrics with a combination of large piezoelectric response and good temperature stability are crucial for high sensitivity and reliability in sensing and actuating devices. However, these two key factors usually do not cooperate with each other especially for lead-free piezoelectric materials, while achieving high piezoelectricity is normally accompanied by poor stability or vice versa. Herein, we report an approach to resolve the incompatibility between piezoelectric coefficient and temperature stability by designing laminated compositions and controlling element diffusion at multi-interfaces, leading to giant piezoelectricity (d 33 ∼450 pC/N) with a minimal variation of about 7 % over a wide temperature range (25°C–90 °C), exceeding the classical lead-free systems. By elaborately modulating the diffusion conditions, the concentration of the element shows a gradually change across the laminated structure, contrast to the terraced distribution of element concentration in traditional laminated structure. Further structure characterization clarifies that the gradually change element concentration contributes to a smooth evolution of crystal structure, which is beneficial for the transition of domain switching between different composition layers, resulting in the improvement of piezoelectric temperature stability. The piezoelectric accelerometer manufactured by modulated ceramics was tested by a vibration system and turned out to be temperature stable compared with commercial PZT-4 sensor. This finding provides an effective and straightforward approach for developing superior ferroelectrics with enhanced temperature stability and high piezoelectric coefficient, promising the potential applications of piezoelectric devices concurrently approaching exceptional sensitivity and thermal reliability. [ABSTRACT FROM AUTHOR]

CaBi 4 Ti 4 O 15 (CBT) ceramics are promising piezoelectric materials that have been widely studied for high-temperature applications. Despite significant advancements in the electrical performance of CBT ceramics, the understanding of their mechanical behaviors remains limited, which is unfavorable for designing ceramics with high stability and reliability during high-temperature service. This work investigated the mechanical properties and fracture behaviors of Nb/Mn co-doped CaBi 4 Ti 4 O 15 (CBTNM) with various doping levels, focusing on stress-strain responses and ferroelastic deformation behaviors under uniaxial compression and multi-field coupling conditions. HRTEM analysis reveals small-scale layered domain wall structures on the surface of plate-like grains. The fracture and compressive strengths of CBTNM ceramics initially decrease and then increase with an increase in doping content, and the underlying mechanisms are related to grain size, defects, and densification. CBTNM ceramics exhibit nonlinear stress-strain responses due to ferroelastic deformation under compressive loading, and the resultant irreversible domain switching strain increases with an increase in doping content, while poling can further increase the residual strain. Under multi-field loading conditions, CBTNM ceramics undergo more ferroelastic deformation events and exhibit larger residual strain. The micro-cracks, pores, complicated fracture modes, and degraded fracture surfaces with fragmental and rough features are mainly responsible for the lower elastic modulus and inferior mechanical response. This work enhances our understanding of the mechanical behaviors of high-temperature piezoelectric ceramics and provides guidance for designing high-performance piezoelectric materials for complex environmental applications. [ABSTRACT FROM AUTHOR]

Antimicrobial materials are crucial for high‐touch surfaces to prevent the adhesion and proliferation of microorganisms, playing a key role in infection control measures. In this work, a magnetoelectric nanocomposite able to exert antimicrobial activity when magnetically stimulated, is obtained by solvent casting. The nanocomposites, composed of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and cobalt ferrite magnetostrictive nanoparticles (CFO NPs), respond to a variable magnetic field by mechanically stimulating the piezoelectric component of the material, thereby inducing an electrical polarization. The antimicrobial properties of the material are determined by exposing it to different frequencies (0.3 and 1 Hz) using a custom‐designed magnetic bioreactor, where the resulting electrical microenvironments are the contributing factor. The growth of Escherichia coli and Staphylococcus aureus over the nanocomposite is highly inhibited when magnetically stimulated (dynamic conditions) mainly at 0.3 Hz, in contrast to static conditions. The electric microenvironment is further measured upon magnetic stimulation, with PHBV films with 20% CFO inducing a voltage variation of ≈20 µV at the surface while the films with 10% CFO induced a voltage variation of ≈12 µV. This work demonstrated that magnetic stimulation, combined with magnetoelectric materials, can be used for remote antimicrobial control, thus preventing the spread of infections. [ABSTRACT FROM AUTHOR]

Energy harvesting from natural sources, including bodily movements, vehicle engine vibrations, and ocean waves, poses challenges due to the broad range of frequency bands involved. Piezoelectric materials are frequently used in energy harvesters, although their effectiveness depends on aligning the device's natural frequency with the frequency of the target energy source. This study models energy harvesters customized for specific applications by adjusting their natural frequencies to match the required bandwidth. We evaluate commercially available piezoelectric transducers and model them using COMSOL Multiphysics alongside an equivalent spring-mass schematic approach, enabling precise adjustments to optimize energy capture. The proposed system achieves a maximum power output of 160 µW and a power density of 187.35 µW/ cm 3 at a natural frequency of 65 Hz. Furthermore, the theoretical maximum power density is calculated as 692.97 W/ m 3 , demonstrating the system's potential for high energy efficiency under optimal conditions. Simulations are validated against experimental data to ensure accuracy. Our findings provide a design framework for optimizing energy harvester performance across diverse energy sources, leading to more efficient and application-specific devices for varied environmental conditions. [ABSTRACT FROM AUTHOR]

Integrally bladed disks (blisks) are extensively used in military and commercial aircraft engines. There are inevitable deviations between blades called mistuning, leading to the vibration localization of blisks, which potentially results in high cycle fatigue (HCF). Furthermore, the dynamic performance is sensitive to mistuning patterns. Hence, to predict the vibration response of mistuned blisks accurately, the mistuning pattern needs to be identified experimentally and verified under traveling wave excitation (TWE). Piezoelectric TWE is a promising testing technique for blisk dynamics in a non-rotating state, offering advantages such as high excitation force, wide bandwidth, and a simple setup. However, piezoelectric materials are generally arranged on blades forming an electromechanically coupled structure, which challenges the existing mistuning identification methods. In this paper, an integral mistuning identification and model updating method with traveling wave excitation verification is developed. The detuning strategy is used to split natural frequencies of blades, whereupon the response is measured blade by blade. Measured response functions of isolated blades can be retrieved by data reconstruction. Then, the mistuning patterns of elastic modulus and damping ratio are identified by Kirchhoff-plate theory and half-power bandwidth method, respectively. Experimental studies are carried out to validate the method. A dummy blisk with piezoelectric patches is designed and the dynamic properties are calculated. Blade-by-blade measurement and TWE test are conducted. Results show that natural frequencies of the updated model are in excellent agreement with the measured ones. Under TWE, the deviations of natural frequencies for all blades are less than 0.25%. The response deviation of the updated model is decreased by 89.4% on average compared with the original model and the average response deviation of the updated model is 7.4%. [ABSTRACT FROM AUTHOR]

This paper presents a new topology optimization scheme for the manufacturable piezoelectric energy harvesters (PEHs). Most of the existing topology optimization schemes for the design of PEHs are difficult to cope with manufacturing constraints producing design results that pose serious challenges for the local poling of the piezoelectric materials. In this work, dual-moving morphable component (dual-MMC) scheme for explicit topology optimization for the design of PEHs is presented. In dual-MMC scheme, two independent sets of MMC are employed to describe the structural topology of the PEH and polarization profile in piezoelectric material in an explicit manner. With the use of the scheme, the shape of electrodes and the opposite polarization directions in the local poling process can be effectively treated as a constraint making the realization of the PEH an easy task. Several examples of the design of cantilever-type PEH are provided to demonstrate the effectiveness of the proposed approach. Furthermore, a designed PEH actually manufactured for demonstration of the production process. [ABSTRACT FROM AUTHOR]

As an emerging sensor technology, the flexible piezoelectric sensor has a very wide range of applications. Therefore, in order to achieve better output performance of flexible piezoelectric sensors, it is particularly important to choose piezoelectric materials with good piezoelectric performance. In this study, polyvinylidene difluoride (PVDF)/polyvinyl chloride (PVC)/graphene oxide (GO) composite fibers were fabricated by the electrospinning technique. FTIR and XRD studies showed that the β-phase content of the composite fibers reached 94.6% with the addition of PVC and GO. The mechanical properties of the composite films doped with PVC and GO were also significantly improved. The sensitivity of the sensor made of composite fibers doped with 0.2 % GO reached 16.2 V/N in the range of 1 N. Compared to other systems, the PVDF/PVC/GO system showed excellent piezoelectric output performance with output voltages of up to 6 V and 3 μA by the action of palm tapping. And after 2000 cycles, the sensor system showed good stability. The resulting flexible piezoelectric sensor can monitor actions such as impacts and bending and has great potential for motion monitoring. [ABSTRACT FROM AUTHOR]

The applications of piezoelectric materials in the field of smart structures have received significant attention from both the communities of science and engineering. Numerous experimental studies have been carried out to endow smart structures with good flexibility. The flexible/stretchable piezoelectric materials are developed to fit this emerging trend. Generally, these materials undergo significant deformation before reaching fracture failure, and they often exhibit a stress-softening phenomenon during the deformation process. However, the traditional linear constitutive model, typically used for rigid piezoelectric ceramics, continues to dominate theoretical and modeling processes in many scenarios. Existing nonlinear constitutive models usually introduce additional coefficients besides elastic, piezoelectric, and dielectric coefficients. Determining these coefficients requires a substantial number of experiments. In this work, based on a Neo-Hookean material model and electromechanical theory, a novel model for flexible piezoelectric material considering large deformation has been established. In contrast with existing models, the present model describes the nonlinear behavior of flexible piezoelectric material without the need for introducing additional parameters. Furthermore, this model exhibits a quadratic dependence of stress on the electric field. To facilitate practical applications, the constitutive model has been implemented using the commercial simulation software ABAQUS through a user subroutine. The accuracy of the subroutine is validated by comparing simulations with analytical solutions for uniaxial stretching of a flexible piezoelectric ribbon. Several numerical examples are followed to demonstrate the robustness of the elements. The proposed model offers a valuable tool for the analysis and design of flexible piezoelectric material. [ABSTRACT FROM AUTHOR]

Defect chemistry that results in the thermal processing of dielectric and piezoelectric films, crystals and ceramics ultimately controls the properties and long‐term performance of materials and devices. This paper reviews several thermochemical defect reactions using important perovskite base composition dielectrics including Pb(Zr,Ti)O3, (Na,K)NbO3, (Bi0.5Na0.5)TiO3‒BaTiO3, and Ca(Hf,Ti,Mn)O3. Within this group of perovskite‐based functional materials, we note ways the point defects can be formed to create non‐stoichiometric compositions changing the overall cation‐to‐anion ratios during the synthesis process. These reactions can be developed with the loss of volatile species such as metal and oxygen ions. The relative concentrations of these can impact the over conductions in terms of the mixed contributions of ionic conductivity from the oxygen vacancies and the electronic conductivity, along with microstructure and properties in some cases. [ABSTRACT FROM AUTHOR]

Specialized sensors in wireless networks monitor the environment with minimal power, which is typically provided by batteries but it can also be powered with renewable sources using smart materials. One such solution is piezoelectric wind energy harvesting to power these sensors. However, the low output power of piezoelectric materials is still a concern. This research aims to improve piezoelectric wind energy harvesting by modifying the geometry of the bluff body. A square-shaped bluff body is used as a reference, and geometric changes are made by attaching square-shaped extensions. The study creates a mathematical model of a cantilever beam system with a piezoelectric material at fix end and a bluff body at the free end, using a multi-physics approach that combines electromechanical and aerodynamic models. The study uses MATLAB Simulink to solve the differential equations and verify the results with experiments. A parametric analysis examines the impact of external resistance, wind speed, and bluff body shape on circuit metrics. The study found that at a wind speed of 6 m/s and an optimal load resistance of 200 kΩ, the system generated 4.984 mW of power. This result demonstrates the potential of wind energy harvesting to power various distributed sensors for a wide range of applications. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel homogenization method for piezoelectric composites with periodic microstructures. In the proposed homogenization method, one can find the analytical expressions for the material properties of the composites in the representative volume element (RVE) via diffused material interface method. The availability of analytical expressions for the material properties in the entire domain of the RVE enables one to determine the effective homogenized material properties with the standard finite element method. As the proposed homogenization method regularizes the discontinuity in material properties across the interfaces, there is no need to explicitly track the material interfaces while implementing the finite element method for determining the effective material properties. Hence, one can implement the proposed homogenized method for any piezoelectric composites with complicated material interfaces and determine the effective material properties. In this study, we have considered the piezoelectric composites to be comprised of periodic microstructures where the RVE constitutes a matrix with an inclusion of a specific shape. We have carried out a study on the effect of the shape of inclusion viz. square-shaped, I-shaped, T-shaped, and plus-shaped, and the size of inclusion on the effective piezoelectric material properties. We have also studied the influence of shape and size of inclusion on the electro-mechanical response of a homogenized piezoelectric continuum. To implement the proposed homogenization method, we have used Gridap, an open-source finite element toolbox in Julia that provides very compact codes freely available to all the researchers and makes a third-party verification of the proposed method straightforward. [ABSTRACT FROM AUTHOR]

Despite the significant advancements in piezoelectric materials for sonodynamic therapy (SDT), the suppression of orthotopic glioma remains challenging, primarily due to the unclear mechanism and the restriction of blood-brain barrier (BBB). Herein, we proposed that layered piezoelectric SrBi 2 Ta 2 O 9 nanoparticles (SBTO NPs) could effectively depolarize the mitochondrial membrane potential (ΔΨ m) of glioma cells under ultrasound (US) exposure. The US-induced band bending in SBTO NPs enhanced redox ability, promoting an increase in reactive oxygen species (ROS) generation. The in vitro results proved that SBTO NPs selectively accumulated in mitochondria under US and induced apoptosis in a mitochondrial depolarization manner mediated by the generation of ROS and free charges. Furthermore, SBTO NPs could cross the BBB and then accumulate in gliomas through US/microbubbles (MBs) procedure and protein-mediated transport. The therapeutic effect of piezoelectric SBTO NPs mediated SDT was proved in the orthotopic glioma mouse model. As validated by the histopathological observation and the long-term evaluation, the good biocompatibility and biosafety of SBTO NPs make it possible for deep tumor therapy, and worthy for further preclinical study. Employing piezoelectric sonosensitizers for sonodynamic therapy (SDT) has emerged as a promising strategy for cancer treatment; however, the unclear mechanism and blood-brain barrier (BBB) limit the effectiveness of SDT in glioma. Herein, we developed piezoelectric SrBi 2 Ta 2 O 9 nanoparticles (SBTO NPs) with a built-in electric field for glioma treatment and explored the underlying therapeutic mechanism. Notably, SBTO NPs selectively accumulated in mitochondria under ultrasound (US) and induced apoptosis in a mitochondrial depolarization manner, which is mediated by the generation of reactive oxygen species (ROS) and free charges. In an orthotopic glioma mouse model, SBTO NPs were delivered into the glioma through US/microbubbles and transferrin-mediated transport pathways, inhibiting tumor growth. This work provides a new paradigm for the treatment of orthotopic glioma and other tumor types. [Display omitted] [ABSTRACT FROM AUTHOR]

The current study analyzed the piezoelectrically driven mechanism responsible for generating force in both rectangular and hummingbird wings, which mimicked the flapping motion of the micro air vehicles, utilizing a combination of numerical simulation and experimental approaches. Digital image correlation technology was employed within the experimental setup to capture the dynamic deformation pattern of the flapping wing, yielding dynamic deformation data. This dataset was subsequently integrated into the computational fluid dynamics (CFD) simulation software to explain the aeroelastic effects. In this way, the dynamic deformation data played a crucial role in computing inertial forces regarding wing flexibility. In addition, temporal force variations generated by the flapping wing were measured using a load cell. The numerical results provided a full understanding of the flapping wing's unsteady aerodynamics, with an emphasis on vortex formations and pressure distribution. We thoroughly examined the force produced by the piezo-actuated flapping wing system. This analysis was then rigorously compared with the data obtained from the load cell measurements. Our primary emphasis was on the vertical forces along the z-axis. Moreover, a thorough comparison of the combined CFD and experimental data inertial results revealed an overall agreement in the total forces from the load cell. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have been proposed as embedded power source, which are capable of converting mechanical energy into electrical energy. However, power generated from a piezoelectric material usually comes with poor characteristics such as high voltage, low current and high impedance. In order to drive the embedded sensor circuit, piezoelectric power needs to be characterized and regulated. In this paper, we present an analysis on the power generation characteristics of the stiff lead zirconate titanate (PZT) ceramics and its equivalent circuit. It is then verified by simulation and experimental results. Since a single PZT element may not meet the needs of real-world embedded applications, we present experiments and analysis using four identical PZTs. Finally, we outline an application where PZT elements are used for power generation in a Total Knee Replacement (TKR) implant. [ABSTRACT FROM AUTHOR]

The kinetic energy is rich in human walking, which may be exploited to provide sustainable energy for portable and miniaturized devices by properly design of the energy harvester. In order to effectively amplify the actual force on the piezoelectric material upon the external load, a beam-shaped piezoelectric energy harvester (PEH) is designed. The PEH is prepared by embedding poly(vinylidene fluoride) (PVDF) piezoelectric strips into the compression zone of the beam. The underlying mechanism is discussed via mechanical theoretical modeling and finite element simulation. It is demonstrated that the actual integrated force on the piezoelectric film of PVDF is about 31.7 times that of the external force applied on the beam's mid-span. The study would pave the way for force amplification mechanism in designing PEHs and holds promises for portable device applications. [ABSTRACT FROM AUTHOR]

BACKGROUND: Piezoelectric catalysis using perovskite‐type barium titanate (BaTiO3) has been applied to the decomposition of refractory organic pollutants through piezoelectric catalytic persulfate (PS). Nevertheless, challenges such as a limited specific surface area, poor electrical conductivity and a tendency towards agglomeration in BaTiO3 necessitate the exploration of novel methods to enhance its piezoelectric efficiency. RESULTS: Sludge carbon (SC) from sewage treatment and BaTiO3 was utilized to develop a novel piezoelectric catalytic material (BaTiO3/SC). The specific surface area of BaTiO3/SC reached 67.92 m2 g−1, which is nine times larger than that of BaTiO3 alone. The inclusion of SC in the composite enhanced the number of active sites and contributed to a higher degree of graphitization, improved electrical conductivity, and provided a more stable structure for BaTiO3/SC. This material was capable of harvesting mechanical vibration energy from ultrasound, thereby generating piezoelectric catalytic properties and activating PS to achieve a 93% decomposition ratio of enrofloxacin (ENR) in water within 80 min. The activation of PS by BaTiO3/SC piezocatalysis led to the production of reactive oxygen species (ROS), such as •OH and SO4−•. These ROS attack the quinolone ring of ENR, which is susceptible to cleavage, resulting in the decomposition of ENR into intermediates of lower toxicity. CONCLUSION: The incorporation of SC has enhanced the piezoelectric performance of BaTiO3, rendering BaTiO3/SC a novel perovskite‐type piezoelectric catalytic material that improves piezoelectric efficiency. The BaTiO3/SC system, through its piezoelectric catalytic activation of PS, demonstrates potential for decomposition of refractory organic pollutants in water treatment. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Despite the promising potential of piezo‐catalysis in environmental remediation applications, the performance of various piezoelectric materials still suffer from low carrier concentrations, limited carrier mobility, and rapid recombination of electron‐hole pairs, and the reported modification strategies are quite intricate and challenging to implement. Herein, MoS2 with varying degrees of crystallinity is synthesized through drying and thermal treatment processes, and the effect of crystal engineering on the performance of the piezo‐activated peroxomonosulfate (PAP) system is investigated. The MoS2 annealed at 700 °C (M‐700) with a crystallization of 60.4% exhibited superior performance in the PAP system, which can degrade 99.6% of bisphenol A within 30 min with a mineralization rate of 57.0%. The positive correlation among the crystallinity of piezoelectric catalysts, the parameters of piezoelectric performance (d33) and piezo‐catalytic performance within a certain range is proposed. From the density functional perturbation theory (DFPT), the crystalline‐amorphous hybrid of M‐700 provided an appropriate charge transfer rate, electron concentration, and mechanical strength, which is more conducive to stimulate the active species chain reaction of PMS. This study provides a novel method for improving the piezo‐catalytic activities and holds great promise for water pollution treatment. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic molecular ferroelectrics have emerged as promising materials for multifunctional piezoelectric devices. However, they present challenges in practical applications because of their inherent brittleness and poor ductility. Herein, we present a flexible mechano-optical dual-responsive molecular ferroelectric composite by incorporating trimethylchloromethyl ammonium (TMCM)-MnCl3 into styrene ethylene butylene styrene (SEBS) matrix. The SEBS/TMCM-MnCl3 exhibits excellent stretchable mechanical properties (tensile strain >1300%, thickness of 30 μm), piezoelectricity, and photoluminescence, enabling advanced visual-tactile- fused anticounterfeiting and encryption applications. Anticounterfeiting and antitampering tags are developed to judge whether the valued items are true or tampered with based on pattern recognition and piezoelectric response, respectively. Additionally, high-security password keyboards featuring triple-layer encryption are designed, offering more password combinations (524,288 times greater than those of traditional password devices relying solely on digital encryption) and enhanced security reliability against cracking attempts. This work can inspire designs of multifunctional optoelectronic materials and enable visual-tactile- fused intelligent applications in human-machine interfaces, information security, and advanced robotics. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are nanoscale tubular materials with superior mechanical strength and electronic properties. However, the conventional CNTs are inherently non‐piezoelectric, mainly due to the lack of polar structures with pure carbon elements. The direct synthesis of fully conjugated and polarized organic nanotubes with desired piezoelectric properties remains a challenge. Herein, we report the bottom‐up synthesis of a new type of covalent triazine‐based nanotube (CTN‐1) as a novel piezoelectric material. The CTN‐1 comprises of high surface area, nitrogen‐rich and fully conjugated structure, which provides a series of merits for piezoelectric catalytic processes. These structural features combined with one‐dimensional tubular morphology endow CTN‐1 with excellent mechanical stimuli response and thus displaying prominent piezoelectric properties via pronounced nanocurvature effect. We further show that the CTN‐1 enables the efficient synthesis of H2O2 from water in the air via mechanical energy conversion, with an excellent piezocatalytic H2O2 evolution rate of 4115 μmol g−1 h−1, which exceeds other reported piezoelectric materials. The piezocatalysis by the CTN‐1 can be practically integrated into a self‐Fenton system, which exhibits excellent pollutant degradation capability. This work demonstrates the enormous potential of a new type of piezoelectric synthetic nanotube from organic frameworks for the in situ synthesis valuable chemicals. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) is a widely recognized piezoelectric ceramic exhibiting excellent dielectric and ferroelectric properties over a wide range of temperature and frequency, making it desirable for applications such as capacitors, piezoelectric transducers, and actuators. Being subjected to repeated electrical loading in various applications, a progressive decrease in the functionality can happen, leading to device failure over time. Therefore, understanding degradation phenomena in all aspects is of importance to expand the lifespan of electronic devices. Despite of many studies focusing on the macroscopic properties of ferroelectrics related to degradation, such as switchable polarization, little is known about the change on local ferroelectric and piezoelectric properties and the domain structure induced by degradation. This paper reports the effect of sub‐coercive electrical cycling on local static and dynamic piezoelectric properties for PZT ceramic using piezoresponse force microscopy (PFM). The piezoelectric properties are probed along the three sample directions (x, y, z) to gain comprehensive insights into the local domain orientation throughout the bulk PZT sample which is then compared with microscopically measured piezoelectric coefficients. The PFM results are analyzed with respect to changes in domain orientation (depolarization) as well as to reduction on piezoelectric material response (degradation) to identify the origin of the degradation behavior. Our results directly show a strong depolarization effect in the direction of the applied electric field because of sub‐coercive cycling although it leads to small or even no degradation in directions perpendicular to the applied electric field. However, the latter is associated with a notable change in dynamic polarization switching properties which are strongly tied to the local domain structure. Our study shows that the origin of the degradation can be identified by analyzing the statistical change of local piezoelectric properties. [ABSTRACT FROM AUTHOR]

This research explored the impact of four different electrolytes on the orientation of cellulose nanocrystals (CNCs) in shear-cast films prepared from aqueous CNC gels. Changes in the aqueous CNC gels' rheological properties with electrolyte addition were correlated to the orientation and optical properties of dried CNC films. Film alignment was qualitatively assessed using cross-polarized optical microscopy and quantified by order parameters computed by UV–Vis transmission spectroscopy. Electrolyte addition resulted in an increased alignment in dried CNC films. For pure CNCs, the film order parameters remained constant at approximately 0.3 for shear rates from 20 s−1 to 100 s−1. However, higher order parameters were achieved in the presence of electrolytes. Notably, an order parameter of 0.88 was achieved at a shear rate of only 20 s−1. In addition, films produced from dispersions containing electrolytes exhibited improved clarity and haze. The results of this work highlight that electrolyte addition can enable higher order parameters at lower shear rates and facilitate the development of aligned CNC films for applications such as polarizers, clear coatings, and piezoelectric materials. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have garnered significant interest owing to width range of applications in sensing and energy harvesting by converting environmental mechanical energy to electricity. Improving the performance of piezoelectric nanogenerators (PENGs) is an important challenge to develop these devices. Herein, a novel method was used to enhance the piezoelectricity of the PENGs based on PVDF NFs (polyvinylidene fluoride nanofibers) and BaTiO3 NPs (barium titanate nanoparticles) by simultaneously electrospinning of PVDF NFs and electrospraying of BaTiO3 NPs. Two set of nanogenerator devices were prepared which differ in piezoelectric layer arrangements and volume fraction of piezopolymer and piezoceramic parts. Results showed that, in case of simultaneously electrospinning and electrospraying (E/E), a significant increase in piezoelectric phase content and voltage output has been observed in comparison with the layer by layer arrangement. The improved piezoelctric performace may result from better dipole alignment facilitated by a more intense electric field during the simultaneously E/E process, along with heightened interactions between the two materials arising from enhanced contact in a multilayer configuration. Moreover, the optimum volume ratio of piezopolymer to piezoceramic to obtain the maximum output was 1.5 to 0.5. Therefore, simultaneously E/E effectively enhance the piezoelectric performance without having the common challenges in the electrospinning process of nanocomposites, as well as decreasing the total preparation time and simplifies the processing steps. Having such features, leads to hold great appeal of these nanogenerators for diverse applications. [ABSTRACT FROM AUTHOR]

In this study, a compact smart bearing with self-sensing and condition monitoring function is proposed. A traditional bearing embedded in a piezoelectric transducer ring with a segmented electrode design is prototyped and tested under different working conditions. Its compact design ensures compatibility for integration with different systems. The segmented electrodes enable possible multidirectional data acquisition and piezoelectric energy generation, suggesting potential integration with Internet of Things (IoT) platforms. Utilizing the high sensitivity, fast response and high signal resolution of the piezoelectric material in conjunction with a novel design that enables close contact between the piezoelectric transducer and the bearing, the smart bearing demonstrates effective performance in detecting weak bearing defects signals. A novel feature characterising method is proposed, and a hybridised feature selection method is employed for reducing the dimension of feature subsets and ensuring defect identification accuracy. A classification model for the identification of defects is developed based on a Long Short-Term Memory (LSTM) network. The performance of the smart bearing and the method for identifying the defects are evaluated through experiments to demonstrate the potential for practical applications. A preliminary experiment for energy harvesting using the smart bearing has been conducted, and it proves the potential to sustain power. [ABSTRACT FROM AUTHOR]

This study proposes a sandwich structure 1-3 piezoelectric composite, incorporating flexible silicone rubber to enhance the thickness vibration mode of piezoelectric ceramics. Rigid aluminum nitride (AlN) is employed to bolster the mechanical stability of the composite. Utilizing equivalent parameter theory, we establish a mathematical model for the sandwich structure composite material. The impact of the piezoelectric phase size and the volume fraction of AlN on several performance parameters of the material are analyzed, including the thickness electromechanical coupling coefficient, density, sound velocity, and characteristic impedance. The sandwich structure piezoelectric composite was fabricated using the "cutting and filling" technique. Experimental outcomes reveal that this material demonstrates concentrated thickness vibration modes, with a thickness electromechanical coupling coefficient reaching as high as 0.72, a 16.6 % increase compared to traditional 1-3 piezoelectric composites. Results from thermal shock tests and tensile tests suggest that the sandwich structure 1-3 piezoelectric composite has considerable potential for use in highly reliable low-frequency receiving transducers. [ABSTRACT FROM AUTHOR]

RF energy harvesting converts ambient signals into electrical power, providing a sustainable energy source. This study demonstrates the use of a piezoelectric transformer for efficient RF energy harvesting. In this work, a piezoelectric transformer (PT) is employed as a high-gain, efficient inverting amplifier to enhance RF wireless energy harvesting. The PT, composed of lead zirconate titanate (PZT), is placed after the receiving loop antenna, with its output connected to an AC-to-DC converter circuit. Maximum harvested power was observed at the PT's resonance frequency of 50 kHz, with an optimal load of 40 kΩ. The system, comprising the antenna, transformer, and rectifier circuit, continues to resonate at 50 kHz, as confirmed by input impedance measurements, demonstrating stable and effective performance. The overall system efficiency was characterized to be 88%. [ABSTRACT FROM AUTHOR]

Cantilever beams with piezoelectric coating are the most widely used form of strain-driven energy harvesting. Almost all prior research on cantilever beam shapes aimed at enhancing energy output accounts for beams fully coated with piezoelectric materials. While a larger coating area, up to a certain limit, can enhance energy output, it also escalates the cost of the structure, as piezoelectric materials are very expensive. Output power density over the length of the beam/piezoelectric material varies significantly. Hence, a partially coated beam with an optimized positioning of piezoelectric material can not only cut the cost of the system but also warrant a higher output power density. On the other hand, optimizing the base beam shape always remains one of the top approaches to increasing the power output. As such, this work aims to select a cantilever beam design by investigating a wide variety of cantilever beam shapes while the beam is partially coated with the piezoelectric material to maximize the power output capacity of the harvester. In the first part of the study, an efficient size of the piezoelectric material and its placement in the host beam are selected based on the power capacity of the system. Next, the selected effective size and placement of the piezoelectric material is implemented in a wide range of cantilever beam shapes (e.g., trapezoidal, triangular, V-cut, concave, and convex) to select a host beam design for maximizing the output power density. To ascertain a comparable argument, the surface area, volume, and mass of all the considered beam shapes are kept consistent, as these parameters influence the power output of the harvester. The geometry of each shape is systematically varied to understand the effect of geometric configuration on the output power density. Additionally, an analysis is conducted to validate that the findings/selection of this study are independent of the thickness of the host beam or piezoelectric material. [ABSTRACT FROM AUTHOR]

In this work, the development of a flexible Double‐Gate (DG) organic thin film transistor (DG‐OTFT), and its employment is reported for the realization of multimodal tactile sensors. Due to the self‐encapsulation of the stacked DG architecture, highly stable organic transistors are obtained that show almost negligible degradation after 6 months. Moreover, such configuration is also very useful for the development of sensing devices. In the case, one of the two gates is used to bias and set the working point of the devices, whereas the second one is connected to a polyvinylidene fluoride(PVDF)‐capacitor, a pyro/piezoelectric material. It is demonstrated that the charge displacement induced by the PVDF capacitor due to an applied external pressure or due to a temperature variation led to a reproducible variation of the device's output current. Using this approach high‐performing multimodal tactile sensors are obtained with sensitivity to up to 241 nA N−1 and 442 nA °C−1 respectively. [ABSTRACT FROM AUTHOR]

This paper has reported a novel ternary system consisting of (1- x - y) BiScO 3 - x PbTiO 3 - y CaZrO 3 (y CZ-BS- x PT). The phase structure, microstructure and electrical parameters of the new piezoelectric material at room temperature were studied in detail. The results showed that d 33 increased significantly with the increase of CZ content. Combined with the results of phase structure, the MPB of 0.02CZ-BS- x PT is located at x = 0.615, which demonstrates optimum piezoelectric performance (d 33 = 470 pC/N， k p = 52.0 %, ε r = 1704). At the same time, the in-situ high-temperature electrical parameters were characterized systematically. It is worth noting that the in-situ electrical parameters are more attractive. When the temperature rises from room temperature to 300 °C, the k t and k p of 0.02CZ-BS-0.615 PT decreases by less than 7 % and the k p reaches the maximum of 60.7 % at 200 °C, and remains 49.8 % even at 300 °C. In addition, the in-situ d 33 test of 0.005CZ-BS-0.63 PT showed that the d 33 of the material increased from room temperature to 424 °C, reaching a maximum of 690 pC/N. From room temperature to 300 °C, the change rate is only 26 %, lower than that of the undoped BS-PT, which is 38.6 %. And the d 33 * reaches a maximum of 994 p.m./V at 200 °C. The improved in-situ piezoelectric properties of y CZ-BS- x PT ternary system makes it a great candidate for high temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

This study reports the characteristics of a piezoelectric nanogenerator (PENG) consisting of a mixture of polydimethylsiloxane (PDMS) and zinc tin oxide (ZTO) particles (ZTO@PDMS) with different shapes and phases. The output performance of PENGs with crystalline Zinc hydroxystannate(ZHS), amorphous ZTO, and crystalline ZTO of different phases was investigated based on annealing temperature. The fabricated PENGs with amorphous ZTO (a-ZTO) cubes showed a maximum output voltage of ∼4.3V and a current of ∼470 nA with a power of 3.14 μW, which is 249 % higher than that of the crystalline ZTO (c-ZTO) cube-based one. The amorphous ZTO (a-ZTO) nanosphere showed the highest output performance. The surface area of the piezoelectric material affected the residual polarization, which led to different piezoelectric properties. Therefore, we investigated the output performance of PENGs with various shapes while maintaining the same volumes of ZTO cubes and spheres. The molar ratio of the materials was varied during synthesis, revealing that the ZTO cubes have a higher output performance. The polarization-electric loops (P-E loops) showed a high remnant polarization (Pr∼25.89μC/cm2) in ZTO@PDMS films with larger 1103 nm cubes. These values were 170.5 %, 143.7 %, and 113.2 % larger than those observed in ZTO@PDMS films with cubes of size 826 nm, 978 nm, and 1047 nm, respectively. The ZTO nanocubes have a significant advantage in the fabrication of high output performance based on PENGs. [ABSTRACT FROM AUTHOR]

Sonopiezocatalytic therapy is an emerging therapeutic strategy that utilizes ultrasound irradiation to activate piezoelectric materials, inducing polarization and energy band bending to facilitate the generation of reactive oxygen species (ROS). However, the efficient generation of ROS is hindered by the long distance of charge migration from the bulk to the material surface. Herein, atomically thin Bi2O2(OH)(NO3) (AT‐BON) nanosheets are rationally engineered through disrupting the weaker hydrogen bonds within the [OH] and [NO3] layer in the bulk material. The ultrathin structure of AT‐BON piezocatalytic nanosheets shortens the migration distance of carriers, expands the specific surface area, and accelerates the charge transfer efficiency, showcasing a natural advantage in ROS generation. Importantly, the non‐centrosymmetric polar crystal structure grants the nanosheets the ability to separate electron‐hole pairs. Under ultrasonic mechanical stress, Bi2O2(OH)(NO3) nanosheets with the remarkable piezoelectric feature exhibit the desirable in vivo antineoplastic outcomes in both breast cancer model and liver cancer model. Especially, the AT‐BON‐induced ROS bursts lead to the activation of the Caspase‐1‐driven pyroptosis pathway. This study highlights the beneficial impact of bulk material thinning on enhancing ROS generation efficiency and anti‐cancer effects. [ABSTRACT FROM AUTHOR]

The concept of multisource energy harvesting has attracted attention in order to harvest multiple types of energy in a single material. In this work, Pb‐free (Ba,Ca)(Zr,Ti)O3 (BCZT) ceramics were used to investigate a combination of piezoelectric and pyroelectric energy harvesting behavior. The temperature dependence of the permittivity and the pyroelectric coefficient was measured, and the pyroelectric properties of BCZT were expected to improve near its orthorhombic–tetragonal phase transition temperature TO–T (∼40°C). The output voltage and current were measured using a BCZT plate, where the BCZT was oscillated under a temperature gradient to apply mechanical stress and temperature fluctuation simultaneously. The measured output voltage from the combined piezo‐ and pyroelectric contributions at a frequency of 2 Hz and with a load resistance of 10 MΩ was 1.4 times higher than the sole piezoelectric output voltage. The resulting combined output voltage was confirmed by finite element simulation. [ABSTRACT FROM AUTHOR]

Design optimization of multilayer piezoelectric transducers is intended for efficient and practical usage of wideband transducers for fault diagnosis, biomedical, and underwater applications through adjusting layer thicknesses and volume fraction of piezoelectric material in each layer. In this context, we propose a parallel differential evolution (PDE) algorithm to mitigate the complexities of multivariate optimization as well as the computation time to achieve an optimized wideband transducer for the particular application. For lead magnesium niobate-lead titanate (PMN PT)- and PZT5h-based piezoelectric materials, the fitness function is formulated based on uniformity of mechanical pressure at the first three harmonics to achieve wide bandwidth in the required functional frequency range. It is carried out using a one-dimensional model (ODM), while input layer thicknesses and volume fractions of active material are evaluated using PDE. The simulation is performed on a parallel computing platform utilizing three different host machines to reduce computational time. Results of the proposed methodology for PDE are statistically represented in the form of minimum, maximum, mean, and standard deviation of fitness value, while graphically represented in terms of speedup and time. It can be observed that the execution time for parallel DE decreases with the increasing number of cores. [ABSTRACT FROM AUTHOR]

AbstractIn this study, using an analytical and precise solution, the dynamic transverse deflection of a five-layer beam with Prussian core with graphene platelet reinforced composite (GPLRC) under a moving harmonic load on a Pasternak elastic substrate is analyzed. First, the properties of the porous core materials and the piezoelectric layer and surface, which were graphene platelet reinforcements (GPLRs), were defined. The constitutive relations were extended using the Bonilla’s higher-order theory and Hamilton’s principle, relationships were extracted. Finally, using the Laplace method and analytical solution. A parametric analysis is provided to investigate impact of temperature distribution, porosity coefficient, thickness ratio, spring constant, voltage and excitation frequency on the responses. [ABSTRACT FROM AUTHOR]

Developing polymer‐based piezoelectric materials with multistimulus responsiveness is highly desirable for advancing multi‐source energy harvesting in wearable electronics. Inspired by the multifunctionality of muscle fibers, a nanostructure interface engineering strategy to create piezoelectric polymeric nanoheterostructures (PNHs) with remarkable responsiveness to both mechanical and nonmechanical contactless stimuli is introduced. Through precise interfacing of polymer nanofibers with nanoparticles via multiscale‐regulated interface electrostatic and chemical interactions, the study achieves a controlled assembly of stabilized and hierarchically organized nanoheterostructures featuring unique interface‐confined configurations. These configurations induce in situ stabilized dipole orientation and significant geometric stress nano‐confinement at interfaces, crucial for amplifying electricity generation. Compared to conventional polymer nanocomposites, engineered PNHs exhibit dramatically enhanced piezoelectricity, boasting a higher sensitivity of 1065 mV kPa−1 and piezoelectric coefficient of 76.2 pC N−1. Furthermore, PNHs demonstrate superior thermo‐actuated electricity generation under temperature fluctuations through cooperative spontaneous polarizations of constituent nanostructures, yielding a higher pyroelectric coefficient of 3.13 µC m2K−1. Additionally, the design enables photothermally‐activated switchable electricity generation and light‐energy harvesting, achieving a photo‐electric conversion efficiency tenfold higher than nanocomposites. This effective and versatile approach inspires the development of multi‐responsive nanogenerators for multi‐energy harvesting and self‐powered multistimulus‐sensing applications. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) is a projection-based vat photopolymerization 3D printing technique that attracts increasing attention due to its high resolution and accuracy. The projection-based layer-by-layer deposition in DLP uses precise light control to cure photopolymer resin quickly, providing a smooth surface finish due to the uniform layer curing process. Additionally, the extensive material selection in DLP 3D printing, notably including existing photopolymerizable materials, presents a significant advantage compared with other 3D printing techniques with limited material choices. Studies in DLP can be categorized into two main domains: material-level and system-level innovation. Regarding material-level innovations, the development of photocurable resins with tailored rheological, photocuring, mechanical, and functional properties is crucial for expanding the application prospects of DLP technology. In this review, we comprehensively review the state-of-the-art advancements in DLP 3D printing, focusing on material innovations centered on functional materials, particularly various smart materials for 4D printing, in addition to piezoelectric ceramics and their composites with their applications in DLP. Additionally, we discuss the development of recyclable DLP resins to promote sustainable manufacturing practices. The state-of-the-art system-level innovations are also delineated, including recent progress in multi-materials DLP, grayscale DLP, AI-assisted DLP, and other related developments. We also highlight the current challenges and propose potential directions for future development. Exciting areas such as the creation of photocurable materials with stimuli-responsive functionality, ceramic DLP, recyclable DLP, and AI-enhanced DLP are still in their nascent stages. By exploring concepts like AI-assisted DLP recycling technology, the integration of these aspects can unlock significant opportunities for applications driven by DLP technology. Through this review, we aim to stimulate further interest and encourage active collaborations in advancing DLP resin materials and systems, fostering innovations in this dynamic field. [ABSTRACT FROM AUTHOR]

The lightweight structure design is a crucial consideration in the industrial field. Unlike passive structures that rely solely on material stiffness to resist external loads, active structures achieve lightweighting by active change of the internal force-driven deformation. An explicit topology optimization method was introduced for piezoelectric multi-material active structures with the moving morphable components (MMC) method. The proposed method minimizes the total mass of the active structure by simultaneously optimizing the structure topology and the distribution of piezoelectric actuators while satisfying the displacement constraints. To optimize the polarization characteristics for adaptive piezoelectric actuation under complex loading conditions, 3 independent sets of MMCs were utilized. These components describe the distributions of elastic and piezoelectric materials as well as the corresponding polarization characteristics, resulting in a composite active structure with explicit geometric descriptions. Numerical examples demonstrate that, compared to passive structures, multi-material active structures based on piezoelectric actuation can realize structural lightweighting more efficiently. [ABSTRACT FROM AUTHOR]

This paper investigates the nonlinear dynamic deflection, natural frequency, and wave propagation in functionally graded (FG) porous piezoelectric microscale tubes under periodic load, hygrothermal conditions, and an external electric field. The piezoelectric material used to make the smart microtubes has pores that may be smoothly changed or uniformly distributed over the tube wall. Here, three types of porosity distribution are taken into consideration. The nonlinear motion equations are constructed using a novel shear deformation beam theory and the modified couple stress theory (MCST). The nonlinear motion equations are solved using the fourth-order Runge–Kutta technique and the Galerkin approach. The effects of various geometric parameters, porosity distribution type, porosity factor, periodic load amplitude and frequency, material length scale parameter, moisture, and temperature on the nonlinear dynamic deflection, natural frequency, and wave frequency of FG porous piezoelectric microtubes are explored through a number of parametric investigations. [ABSTRACT FROM AUTHOR]