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Highlights Copper based metal–organic frameworks (Cu‐MOF) incorporated poly(vinylidene fluoride) (PVDF) composites were processed using drop casting, with different concentrations of Cu‐MOF (0.15–2 wt.%). Ultrasonication and centrifugation of Cu‐MOF particles were adopted as pre‐processing steps to ensure effective de‐agglomeration of the Cu‐MOF particles. The formation of polar β‐crystalline phase in PVDF/Cu‐MOF composite was confirmed by the morphological observation of fibrillar microstructure and the manifestation of specific absorption bands via spectroscopic analysis. Further, FTIR and NMR spectroscopic analyses unequivocally established the interfacial interactions between Cu‐MOF particles and PVDF dipoles. A maximum of ~92% polar fraction and ~25 pm/V d33 was obtained in PVDF composite of 1 wt.% of Cu‐MOF. Dielectric and ferroelectric investigations were carried out to relate the improvement of the interfacial polarization. Moreover, energy harvesting devices were fabricated from PVDF/MOF composites and a maximum rectified piezoelectric voltage of ~40 V was recorded during finger tapping experiment in PVDF/MOF composite of 1 wt.% Cu‐MOF. Further, a load current and maximum volumetric power density of 7.5 μA and ~1.2 mW/cm3, respectively, were achieved. The usage of the fabricated device as an energy harvester was further established by charging and discharging different capacitors and illuminating LEDs. Cu‐MOF (0.15–2 wt.%) incorporated PVDF composites were processed by solution casting. A maximum of ~92% polar fraction was obtained in PVDF/1MOF composite. A maximum rectified output voltage of ~40 V was recorded in PVDF/1MOF composite. A higher power density (1.2 mW/cm3) and load current (7.5 μA) were achieved for PVDF/1MOF. The usage of the fabricated device as an energy harvester was further established. [ABSTRACT FROM AUTHOR]

Piezoelectric nanostructures have attracted significant attention owing to their capacity for converting mechanical energy into electrical energy, enabling applications in biomedical fields, actuators, and energy harvesting devices. Boron nitride nanotubes (BNNTs) exhibit unique properties that make them attractive candidates for piezoelectric applications. However, the influence of BNNT chiralities on their piezoelectric behavior has not been thoroughly explored. In this study, we investigated the piezoelectric effect of zigzag and armchair chiralities of BNNT structures, aiming to elucidate the relationship between chirality and piezoelectric response by discovering a novel protocol for simulating the electrical behavior of BNNTs at the nanoscale level. We employed a computational method to examine the piezoelectric potential of BNNT structures. First, we established an equivalent-sized three-dimensional (3D) model of zigzag and armchair BNNT structures using nanotube modeler software. The obtained models were then subjected to mesh analysis to generate finite element method simulations. The simulations were finally performed to analyze the electrical response of the BNNT structures under external mechanical forces. We observed that the electrical responses of zigzag BNNT were 1.6 times greater than armchair one. In conclusion, our study sheds light on the piezoelectric potential of zigzag and armchair chiralities of BNNT structures. Furthermore, our findings contribute to the understanding of the electrical properties of BNNTs and their potential for various medical and industrial applications. The knowledge gained from this study provides a foundation for further research and development in the field of piezoelectric nanostructures, paving the way for innovative advancements in nanotechnology. [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalytic mechanism and material preparation based on the piezoelectric effect. • The application of the piezoelectric effect in wastewater purification is expounded. • The development of the piezoelectric effect-assisted water purification technology. • The challenges and prospects of the piezoelectric effect in wastewater purification. The demands of human life and industrial activities result in a significant influx of toxic contaminants into aquatic ecosystems. In particular, organic pollutants such as antibiotics and dye molecules, bacteria, and heavy metal ions are represented, posing a severe risk to the health and continued existence of living organisms. The method of removing pollutants from water bodies by utilizing the principle of the piezoelectric effect in combination with chemical catalytic processes is superior to other wastewater purification technologies because it can collect water energy, mechanical energy, etc. to achieve cleanliness and high removal efficiency. Herein, we briefly introduced the piezoelectric mechanisms and then reviewed the latest advances in the design and synthesis of piezoelectric materials, followed by a summary of applications based on the principle of piezoelectric effect to degrade pollutants in water for wastewater purification. Moreover, water purification technologies incorporating the piezoelectric effect, including piezoelectric effect-assisted membrane filtration, activation of persulfate, and battery electrocatalysis are elaborated. Finally, future challenges and research directions for the piezoelectric effect are proposed. [ABSTRACT FROM AUTHOR]

Understanding the structure and function of bioelectric materials is challenging due to the complex nature of biomaterials and a lack of appropriate tools. The precisely defined structures and genetic tunability of viruses provide an excellent model system to investigate bioelectrical behavior in biomaterials. This study presents the molecular mechanisms of piezoelectricity in the M13 bacteriophage (phage) under various mechanical stresses for bio‐piezoelectric generation. A computational approach is used to calculate the piezoelectric tensors of the M13 phage and quantify its direction‐dependent dipole moments. By computationally designing negatively charged residues on the phage surface, the surface charge density is enhanced to 16.7 µC cm−2. Using genetic engineering, phages are experimentally designed with different charges and tail structures to create model phage nanostructures, including individual phages, vertically standing phage films, and horizontally aligned phage films. Their vertical, horizontal, and shear‐mode piezoelectric properties are then measured using scanning probe microscopy techniques. The resulting phage‐based piezoelectric energy generators exhibit an effective piezoelectric coefficient of 15.4 pm V−1 and a power density of 4.2 µW cm−2. This phage‐based bioengineering approach provides a versatile platform for investigating fundamental mechanisms of bioelectricity and designing bioelectric materials for applications in energy harvesting, biomemory, and biosensors. [ABSTRACT FROM AUTHOR]

Organic and metal-free molecules with piezoelectric and ferroelectric properties have gained wide interest for their applications in the domain of mechanical energy harvesting due to their desirable properties such as light weight, thermal stability, mechanical flexibility, feasibility to achieve high Curie temperatures, and ease of synthesis. However, the understanding and design of these materials for piezoelectric energy harvesting applications is still in its early stages. This review paper presents a comprehensive overview of the fundamental characterization of piezoelectricity for a range of organic ferro- and piezoelectric materials and their composites. It also discusses the limitations of traditional piezoelectric materials and highlights the advantages of organic materials in this area in the introduction part. In addition, the paper provides a detailed description of peptide-based and other biomolecular piezoelectric materials as a bio-friendly alternative to current materials. This perspective aims to guide researchers in designing functional organic materials and composites for practical mechanical energy harvesting applications and to highlight current limitations and future perspectives in this emerging area of research. [ABSTRACT FROM AUTHOR]

With advances in technology, the generation of electrical energy through the harvesting of energies dissipated in the form of mechanical vibration, known as power harvesting, has received increasing attention in recent decades. It is undoubtedly an interesting means to power systems with low energy consumption. This research aims to evaluate an energy generation system based on the piezoelectric effect activated by mechanical excitation and develop a system capable of powering devices and sensors for temperature monitoring in a practical situation, such as in an engine room, aiming to ensure its safe operation. Two transducers subjected to vibrational excitation were evaluated, and then an energy generation system using a buck DC-DC converter circuit was assessed. The transducer was connected to the input of the board, the microcontroller to the output, and the LM35 temperature sensor along with the battery was used to ensure the circuit's autonomy. Additionally, the Attiny85 microcontroller was programmed to perform temperature monitoring tasks in a continuous low-energy-consumption mode. The obtained spectral analysis results showed a maximum generation power of 8.88 mW for the PZT-5H transducer and 3.3 mW for the P5-13B transducer. The use of LTC3588-1 increased the autonomy of the monitoring system by 64.3% and reduced the system's usage time in cases of temperature anomalies by 50%. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model is formulated to analyze the linear longitudinal forced vibration response of a PZT nano-generator acting on its 33-mode for energy harvesting and the effects of both steady-state and transient vibration response of the nano-generator are taken into consideration. Computer simulations are carried out to investigate the generated power, voltage and current originating from the excitation of the base motion. The effects of the excitation frequency, whether it is in the near resonance domain or not, the resistance of the electrical circuit and the nanorod's aspect ratio on the vibration response and electrical response of the nanogenerator are evaluated. For this purpose, Eringen's differential model, Hamilton's principle, the linear piezoelectricity theory and the classical rod theory are employed to derive the governing equation of motion together with the equivalent electrical equation. Then, the derived equations are solved using the Laplace transform method and several results such as the peak voltage as a function of the exciting frequency are shown to demonstrate the effectiveness of the proposed methodology. [ABSTRACT FROM AUTHOR]

Bone repair and regeneration require physiological cues, including mechanical, electrical, and biochemical activity. Many biomaterials have been investigated as bioactive scaffolds with excellent electrical properties. Amongst biomaterials, piezoelectric materials (PMs) are gaining attention in biomedicine, power harvesting, biomedical devices, and structural health monitoring. PMs have unique properties, such as the ability to affect physiological movements and deliver electrical stimuli to damaged bone or cells without an external power source. The crucial bone property is its piezoelectricity. Bones can generate electrical charges and potential in response to mechanical stimuli, as they influence bone growth and regeneration. Piezoelectric materials respond to human microenvironment stimuli and are an important factor in bone regeneration and repair. This manuscript is an overview of the fundamentals of the materials generating the piezoelectric effect and their influence on bone repair and regeneration. This paper focuses on the state of the art of piezoelectric materials, such as polymers, ceramics, and composites, and their application in bone tissue engineering. We present important information from the point of view of bone tissue engineering. We highlight promising upcoming approaches and new generations of piezoelectric materials. [ABSTRACT FROM AUTHOR]

This work embarks on an exploration of piezoelectric energy harvesting (PEH), seeking to unravel its potential and practicality. PEH has emerged as a promising technology in the field of civil engineering, offering a sustainable approach to generating energy from ambient mechanical vibrations. We will explore the applications and advancements of PEH within the realm of civil engineering, focusing on publications, especially from the years 2020 to 2024. The purpose of this study is to thoroughly examine the potential and practicality of PEH in civil engineering applications. It delves into the fundamental principles of energy conversion and explores its use in various areas, such as roadways, railways, bridges, buildings, ocean wave-based energy harvesting, structural health monitoring, and even extraterrestrial settings. Despite the potential benefits of PEH in these domains, there are significant challenges that need to be addressed. These challenges include inefficient energy conversion, limitations in scalability, concerns regarding durability, and issues with integration. This review article aims to address these existing challenges and the research gap in the piezoelectric field. [ABSTRACT FROM AUTHOR]

Atomic oxygen (AO) in low Earth orbit (LEO) can cause severe progressive damage to spacecraft orbiting at hypervelocities over 7 km/s; therefore, all space-graded materials need to be qualified for protection against these high energy impacts. Instead of treating AO as a threat, can we use these atomic impacts, which have enough energy to cause material failure, to generate power? Despite its potential, no attempt has yet been made to utilize the hypervelocity impact energy of AO. Thus, we propose a piezoelectric energy harvesting method through the hypervelocity AO impact in LEO. In this study, energy harvesting with various configurations was experimentally demonstrated using a conventional lead zirconate titanate (PZT) ceramic plate under oxygen plasma exposure to simulate AO impact. The average output power density was 4 W/m2 under 1.43 × 1016 atoms/cm2s effective AO flux conditions. Our study provides a new method for generating energy in a space environment with limited energy sources. [Display omitted] • Energy harvested from hypervelocity atomic oxygen impact in low Earth orbit. • Piezoelectric energy harvesting at atomic level in simulated space environment. • Output power density of approximately 4 W/m2 from PZT-5A under oxygen plasma. • Challenges and potential of atomic oxygen as a space energy source discussed. [ABSTRACT FROM AUTHOR]

The transformation of environmentally benign waste energy into functional electricity holds profound implications for advancements in human progress. Herein, we detail the synthesis of tubular nanofibers featuring a hollow architecture through an innovative combination of sol-gel processing and electrospinning techniques, followed by surface modification with dopamine. These engineered PZT hollow nanotubes, upon integration into PVDF piezoelectric films, serve as potent reinforcing agents that amplify the piezoelectric active phase within the PVDF matrix. The introduction of these hollow PZT nanostructures alters the polarization electric field distribution, thereby augmenting the polarization dynamics of PVDF and significantly enhancing the piezoelectric performance of the resultant PVDF/PZT composite films. Our novel nano-generator exhibits an exceptional balance between a high piezoelectric coefficient, superior output characteristics, and commendable stability. Notably, the piezoelectric constant (d 33) of Neat PVDF films experiences a substantial elevation from 9 pC N−1 to 20 pC N−1, representing an impressive enhancement of approximately 122 %. Furthermore, the power density achieves a value of 0.54 μW cm−2. This study introduces an effective approach to augment the productive output capability of composite nanogenerators, paving the way for sustainable energy harvesting technologies. [ABSTRACT FROM AUTHOR]

Piezoelectric vibration isolation and energy harvesting applications have been extensively studied in the literature. The studies include linear and nonlinear approaches. Linear methods are simpler but possess inherent limitations. On the other hand, nonlinear ones could perform better over a broader operating frequency range. Nonlinearity can be introduced in the mechanical domain or electrical domain actively or passively. Since electrical components can be on smaller scales compared to mechanical counterparts, inducing nonlinearity on the mechanical system through the electrical domain can be more practical. Moreover, passive structures require no energy supply and controller therefore they are simpler and more reliable than active ones. In this paper, a novel way to attain passive hardening stiffness was suggested by introducing an electrical component in a shunt circuit for passive nonlinear piezoelectric vibration isolation or energy harvesting applications and the induced structural non-linearity is demonstrated experimentally. A passive nonlinear component is suggested to be a hardening capacitor obtained by the P–N junction. An analytic model is derived for parallel connected macro-fiber composite (MFC) piezoelectric material attached bimorph configuration on a cantilever beam and the model is solved numerically. MFC integrated bimorph model, and P–N junction approximate model are presented. The frequency response of the coupled system is obtained by using numerical models and experiments. Both numerical analysis and experiments validated the hardening stiffness effect of the P–N junction. To the best of the authors' knowledge, this study is the first study to demonstrate that nonlinear capacitance of P–N junctions can be used to attain nonlinearity in a mechanical system. [ABSTRACT FROM AUTHOR]

In this study, we achieved energy localization and amplification of flexural vibrations by utilizing the defect mode of plate-attachable locally resonant metamaterials, thereby realizing compact and low-frequency vibration energy suppression and energy harvesting with enhanced output performance. We designed a cantilever-based metamaterial unit cell to induce local resonance inside a periodic supercell structure and form a bandgap within the targeted low-frequency range of 300–450 Hz. Subsequently, a defect area was created by removing some unit cells to break the periodicity inside the metamaterial, which led to the isolation and localization of the vibration energy. This localized vibration energy was simultaneously converted into electrical energy by a piezoelectric energy harvester coupled with a metamaterial inside the defect area. Consequently, a substantially enhanced energy harvesting output power was achieved at 360 Hz, which was 43-times higher than that of a bare plate without metamaterials. The proposed local resonant metamaterial offers a useful and multifunctional platform with the capability of vibration energy isolation and harvesting, while exhibiting easy handling via attachable designs that can be tailored in the low-frequency regime. Highlights: • Compact multifunctional vibration isolation-energy harvesting metastructures based on a low-frequency defect bandgap. • Enhanced harvesting power by a factor of 43 over a wide frequency range of 310-380 Hz • Easily mass-produced metamaterial unit cell via a laser-cutting process. • Multifunctionality, i.e., vibration isolation and harvesting, proved by a carefully-designed experiment. [ABSTRACT FROM AUTHOR]

Organic piezoelectric nanogenerators (PENGs) are attractive in harvesting mechanical energy for various self‐powering systems. However, their practical applications are severely restricted by their low output open circuit voltage. To address this issue, herein, we prepared two two‐dimensional (2D) covalent organic frameworks (COFs, CityU‐13 and CityU‐14), functionalized with fluorinated alkyl chains for PENGs. The piezoelectricity of both COFs was evidenced by switchable polarization, characteristic butterfly amplitude loops, phase hysteresis loops, conspicuous surface potentials and high piezoelectric coefficient value (d33). The PENGs fabricated with COFs displayed highest output open circuit voltages (60 V for CityU‐13 and 50 V for CityU‐14) and delivered satisfactory short circuit current with an excellent stability of over 600 seconds. The superior open circuit voltages of CityU‐13 and CityU‐14 rank in top 1 and 2 among all reported organic materials‐based PENGs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel S-scheme NiO/PbBiO 2 Br composites are synthesized through a hybrid approach combining hydrothermal and photodeposition methods. • NiO/PbBiO 2 Br composites demonstrate dual energy harvesting capabilities from solar and vibration sources. • A synergistic effect between piezocatalysis and photocatalysis is observed in NiO/PbBiO 2 Br. • NiO/PbBiO 2 Br exhibits significantly increased photoactivity in RhB degradation. • Enhanced charge separation efficiency is achieved in NiO/PbBiO 2 Br via an S-scheme mechanism. The fabrication of an S-scheme heterojunction demonstrates as an efficient strategy for achieving efficient charge separation and enhancing catalytic activity of piezocatalysts. In this study, a new S-scheme heterojunction was fabricated on the PbBiO 2 Br surface through the photo-deposition of NiO nanoparticles. It was then employed in the piezoelectric catalytic degradation of Rhodamine B (RhB). The results demonstrate that the NiO/PbBiO 2 Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO 2 Br synthesized after 2 h of irradiation, achieving a RhB degradation rate of 3.11 h−1, which is 12.4 times higher than that of pure PbBiO 2 Br. Simultaneous exposure to visible light and ultrasound further increases in the RhB degradation rate, reaching 4.60 h−1, highlighting the synergistic effect of light and piezoelectricity in the NiO/PbBiO 2 Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO 2 Br heterojunction was undertaken through electrochemical analyses, theoretical calculations, and in-situ X-ray photoelectron spectroscopy analysis. The outcomes reveal that p-type semiconductor NiO and n -type semiconductor PbBiO 2 Br possess matching band structures, establishing an S-scheme heterojunction structure at their interface. Under the combined effects of band bending, interface electric fields, and Coulomb attraction, electrons and holes migrate and accumulate on the conduction band of PbBiO 2 Br and valence band of NiO, respectively, thereby achieving effective spatial separation of charge carriers. The catalyst's synergistic photo-piezoelectric catalysis effect can be ascribed to its role in promoting the generation and separation of charge carriers under both light irradiation and the piezoelectric field. The results of this investigation offer valuable insights into the development and production of catalytic materials that exhibit outstanding performance through the synergy of piezocatalysis and photocatalysis. [ABSTRACT FROM AUTHOR]

Hybrid nanogenerators are advanced mechanical energy harvesters capable of simultaneously scavenging multiple types of energy. Additionally, thermochromic materials provide a practical and visually assessable method for real‐time temperature monitoring. In this report, a novel energy harvester and sensing patch (EHSP) is introduced, that utilizes combined piezoelectric and triboelectric effects to harvest mechanical energy efficiently. To optimize the EHSP, various energy harvester configurations are fabricated and tested, and the dielectric properties of triboelectric films are systematically investigated. These improvements are implemented to augment the overall energy harvesting capability. The thermochromic properties of the EHSP are also explored to enhance both the electrical performance and thermal responsiveness. The EHSP demonstrates the ability to generate maximum voltage and current outputs of 350 V and 20.4 µA, respectively. Moreover, it can detect temperature changes within seconds, making it suitable for both energy harvesting and sensing applications. The EHSP is tested in practical scenarios, proving its efficiency as an energy harvester and sensor for everyday human activities. Furthermore, its integration with multiple hybrid nanogenerators showcases its potential for industrial and wearable sensing applications. [ABSTRACT FROM AUTHOR]

Nanogenerators have garnered significant interest as environmentally friendly and potential energy-harvesting systems. Nanogenerators can be broadly classified into piezo-, tribo-, and hybrid nanogenerators. The hybrid nanogenerator used in this experiment is a nanogenerator that uses both piezo and tribo effects. These hybrid nanogenerators have the potential to be used in wearable electronics, health monitoring, IoT devices, and more. In addition, the versatility of the material application in electrospinning makes it an ideal complement to hybrid nanogenerators. However, despite their potential, several experimental variables, biocompatibility, and harvesting efficiency require improvement in the research field. In particular, maximizing the output voltage of the fibers is a significant challenge. Based on this premise, this study aims to characterize hybrid nanogenerators (HNGs) with varied structures and material combinations, with a focus on identifying HNGs that exhibit superior piezoelectric- and triboelectric-induced voltage. In this study, several HNGs based on coaxial structures were fabricated via electrospinning. PVDF-HFP and PAN, known for their remarkable electrospinning properties, were used as the primary materials. Six combinations of these two materials were fabricated and categorized into homo and hetero groups based on their composition. The output voltage of the hetero group surpassed that of the homo group, primarily because of the triboelectric-induced voltage. Specifically, the overall output voltage of the hetero group was higher. In addition, the combination group with the most favorable voltage characteristics combined PVDF-HFP@PAN(BTO) and PAN hollow, boasting an output voltage of approximately 3.5 V. [ABSTRACT FROM AUTHOR]

Piezo‐photocatalysis could coalesce the advantages of mechanical vibration and solar energy perfectly to achieve high‐efficiency catalytic activity. Herein, the quintessential piezoelectric material CdS nanowires with different aspect ratios are precisely constructed and applied for piezo‐photocatalytic reduction of U(VI) for the first time. The ultrasonic (60 kHz, 100 W) induces piezoelectric potential to generate a 0.57 eV A−1 electric field, which is added to the direction of CdS (010) as a driving force to efficiently separate photogenerated charges. The alliance between piezoelectric effect and photocatalytic activity endows CdS NW‐3 with the fastest piezo‐photocatalytic rate under ultrasonic vibration and 5 W LED irradiation, and the relevant rate constant (0.042 min−1) is about 12 and 53.8 times than that of LED and ultrasonication. More importantly, 93.74% of U(VI) could be removed from natural uranium mine wastewater. Therefore, this piezo‐photocatalysis system that reduces U(VI) to easily separable (UO2)O2·2H2O(s) provides valuable input for disposal applications of radioactive wastewater and broadens the horizons of nuclear energy utilization toward the advancement of carbon neutrality. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The inevitable feedback between the environmental and energy crisis within the next decades can probably trigger and/or promote a global imbalance in both financial and public health terms. To handle this difficult situation, in the last decades, many different classes of materials have been recruited to assist in the management, production, and storage of so-called clean energy. Probably, ferromagnets, superconductors and ferroelectric/piezoelectric materials stand at the frontline of applications that relate to clean energy. For instance, ferromagnets are usually employed in wind turbines, superconductors are commonly used in storage facilities and ferroelectric/piezoelectric materials are employed for the harvesting of stray energy from the ambient environment. In this work, we focus on the wide family of ferroelectric/piezoelectric materials, reviewing their physical properties in close connection to their application in the field of clean energy. Among other compounds, we focus on the archetypal compound Pb(Zr,Ti)O3 (or PZT), which is well studied and thus preferred for its reliable performance in applications. Also, we pay special attention to the advanced ferroelectric relaxor compound (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (or PMN-xPT) due to its superior performance. The inhomogeneous composition that many kinds of such materials exhibit at the so-called morphotropic phase boundary is reviewed in connection to possible advantages that it may bring when applications are considered. [ABSTRACT FROM AUTHOR]

Abstract In this study, we achieved energy localization and amplification of flexural vibrations by utilizing the defect mode of plate-attachable locally resonant metamaterials, thereby realizing compact and low-frequency vibration energy suppression and energy harvesting with enhanced output performance. We designed a cantilever-based metamaterial unit cell to induce local resonance inside a periodic supercell structure and form a bandgap within the targeted low-frequency range of 300–450 Hz. Subsequently, a defect area was created by removing some unit cells to break the periodicity inside the metamaterial, which led to the isolation and localization of the vibration energy. This localized vibration energy was simultaneously converted into electrical energy by a piezoelectric energy harvester coupled with a metamaterial inside the defect area. Consequently, a substantially enhanced energy harvesting output power was achieved at 360 Hz, which was 43-times higher than that of a bare plate without metamaterials. The proposed local resonant metamaterial offers a useful and multifunctional platform with the capability of vibration energy isolation and harvesting, while exhibiting easy handling via attachable designs that can be tailored in the low-frequency regime.

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]

In the current electromechanical model of cantilevered piezoelectric energy harvesters, the assumption of uniform electric field strength within the piezoelectric layer is commonly made. This uniform electric field assumption seems reasonable since the piezoelectric layer looks like a parallel-plate capacitor. However, for a piezoelectric bender, the strain distribution along the thickness direction is not uniform, which means the internal electric field generated by the spontaneous polarization cannot be uniform. In the present study, a non-uniform electric field in the piezoelectric layer is resolved using electrostatic equilibrium equations. Based on these, the traditional distributed parameter electromechanical model is corrected and simplified to a practical single mode one. Compared with a traditional model adopting a uniform electric field, the bending stiffness term involved in the electromechanical governing equations is explicitly corrected. Through comparisons of predicted power output with two-dimensional finite element analysis, the results show that the present model can better predict the power output performance compared with the traditional model. It is found that the relative corrections to traditional model have nothing to do with the absolute dimensions of the harvesters, but only relate to three dimensionless parameters, i.e., the ratio of the elastic layer's to the piezoelectric layer's thickness; the ratio of the elastic modulus of the elastic layer to the piezoelectric layer; and the piezoelectric materials' electromechanical coupling coefficient squared, k 31 2 . It is also found that the upper-limit relative corrections are only related to k 31 2 , i.e., the higher k 31 2 is, the larger the upper-limit relative corrections will be. For a PZT-5 unimorph harvester, the relative corrections of bending stiffness and corresponding resonant frequency are up to 17.8% and 8.5%, respectively. An inverse problem to identify the material parameters based on experimentally obtained power output performance is also investigated. The results show that the accuracy of material parameters identification is improved when considering a non-uniform electric field. [ABSTRACT FROM AUTHOR]

Wearable biomechanical energy harvesting devices have received a lot of attention recently, benefiting from the rapid advancement of theories and devices in the field of the micro electromechanical system (MEMS). They not only fulfil the requirements for powering wearable electronic devices but also provide an attractive prospect for powering self-powered flexible electronic devices when wearing. In this article, we provide a review of the theories and devices of biomechanical energy harvesting technology for wearable applications. Three different forms of biomechanical energy harvesting mechanisms, including the piezoelectric effect, electromagnetic effect, and electrostatic effect, are investigated in detail. The fundamental principle of converting other types of energy from the biomechanical environment into electrical energy, as well as the most commonly-used analytical theoretical models, are outlined for each process. Therefore, the features, properties, and applications of energy harvesting devices are summarized. In addition, the coupled multi-effect hybrid energy harvesting devices are listed, showing the various possibilities of biomechanical energy harvesting devices for serving as sources, sensors, and actuators. Finally, we present perspectives on the future trends of biomechanical energy harvesting devices for wearable electronics applications. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Considering the growing demand for piezoelectric energy harvesting from ferroelectric–polymer-based composite materials and the benefits associated with them, this work focuses on piezoelectric energy harvesting from poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP)/BZT-BCT/GO hybrid composite films synthesized via solution casting followed by the hot-pressing method. Structural properties were analyzed using XRD, FTIR, and Raman spectroscopy. SEM micrographs confirmed the presence of pores in the synthesized samples that provided an added advantage toward enhancing its piezoelectricity. The dielectric and ferroelectric properties were studied, in which the dielectric constant increased up to 20.69, and the remnant polarization was found to be 0.0560 μ C cm−2. A PUND analysis was performed to validate the data obtained from the static hysteresis loop. Piezoelectric charge and voltage coefficients were measured, which reach up to "−31 pC N−1" and "−252.5 mV m N−1," respectively. Figure of merit, electromechanical coupling coefficient, and quality factor of the as-synthesized samples were calculated. A harvester prototype was fabricated to investigate the energy harvesting performance of the synthesized hybrid composite films. The highest open circuit voltage, short circuit current, and power density were recorded as 2.19 V, 24.17 nA, and 468.43 μ W m−2, respectively. The harvested energy can be utilized for powering low-power devices, showing the real-time applicability of the synthesized hybrid composite films. [ABSTRACT FROM AUTHOR]

Mechanical energy harvesting performances of poly(vinylidene fluoride) (PVDF) based composites are most often correlated with their polar phase and the individual piezoelectricity of the used filler materials. Here we show that the significant enhancement of space charge polarization of the said composites can play the key dominant role in determining their mechanical energy harvesting performance regardless of their polar phase and individual piezoelectricity of the used fillers. For this purpose, ionic liquid has been incorporated into PVDF/0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Ti0.8Zr0.2)O3 (BCZT) composites which led to a huge enhancement in space charge polarization. The gradual addition of ionic liquid into 10 wt% BCZT loaded PVDF (PBCZT) has helped in extraordinarily enhancing the conductivity gradually which has confirmed the huge enhancement of space charge polarization. However, after a certain limit of ionic liquid addition, the polar phase of the composite films is decreased. Despite this, the output voltages from the piezoelectric and piezo-tribo hybrid nanogenerators (PENGs and HNGs, respectively) fabricated by using the developed films have been found to be increased gradually with the increase in the ionic liquid amount in PBCZT composite. As the amount of BCZT filler was kept fixed for all the films, this result has confirmed the key role of space charge polarization of PVDF-based composites in determining their mechanical energy harvesting performances compared to the effect of polar phase and individual piezoelectricity of filler. The optimized PENG and HNG devices have shown the output voltage as high as 52 and 167 V, respectively, with power densities ∼85 and 152 μ W cm−2 which predicted their excellent usability in real life energy conversion devices. This work also shows that the effect of extraordinarily enhanced space charge polarization is effective in improving the performance of all types of mechanical energy harvesting devices regardless of their mechanisms (piezoelectric or hybrid). [ABSTRACT FROM AUTHOR]

The small‐scale‐dependent nonlinear dynamical attributes of microplate‐type laminated piezoelectric systems of harvesting energy subjected to a triangular mechanical actuation are explored in the current exploration. The core of harvesting systems is supposed to be made of nanocomposites reinforced by randomly oriented carbon nanotubes (CNTs) having various degrees of agglomeration coated by piezoelectric layers. In this regard, the microplate‐type systems of harvesting energy are modeled via a quasi‐3D plate theory combined with the modified strain gradient elasticity in the presence of various microsize‐dependent strain gradient tensors. Thereafter, the solution of the developed coupled electromechanical size‐dependent nonlinear problem is obtained numerically by utilizing the meshless collocation approach employing incorporation of the polynomial and radial basis functions to remove any feasible singularity for the associated moment matrices. It comes to the conclusion that by elevating the quantity of CNTs disclosed within the clusters, the significance of the microsize dependency in the achieved voltage enhances from 22.06% to 22.73% toward the simply supported bridge‐type context, and from 33.00% to 33.92% toward the clamped bridge‐type context. Highlights: Development of a microstructural‐dependent quasi‐3D shear flexible energy harvester model.Incorporating the roles of various strain gradient tensors in the nonlinear dynamics of microharvesters.Size‐dependent time‐histories of achieved voltage from triangular mechanical‐loaded microharvesters.Influence of the CNT reinforcement clustering on the nonlinear dynamic performance. [ABSTRACT FROM AUTHOR]

The temperature instability of piezoelectric properties in KNN-based ceramics has been a major bottleneck impeding them toward practical applications. Herein, we prepared multilayer composite ceramics using two kinds of textured thick films with different polymorphic phase transition temperatures. The composite ceramics simultaneously exhibited outstanding piezoelectric properties (d 33 = 400 ± 20 pC/N; S = 0.18 % at 40 kV/cm) and piezoelectric temperature stability (d 33 and S variation within 5 % and 2 %, respectively over the temperature range of room temperature to 180 °C). The synergistic contribution of slightly fluctuating ε r ·P r values, the robust phase and domain structures, and the complementary effect of piezoelectric fluctuation between the two composite layers led to the outstanding temperature stability of piezoelectric properties. Furthermore, the piezoelectric energy harvester produced using KNN-T 1 /T 2 composite ceramics exhibits a large power density of 5.4 mW/cm3. These results prove great potential of KNN-T 1 /T 2 ceramics in high temperature piezoelectric devices. [ABSTRACT FROM AUTHOR]

Mechanoluminescence (ML) is luminescence induced due to mechanical stress, providing intuitive responses to strain‐related events. Piezoelectricity is the conversion of mechanical strain into electrical signals, offering a quantitative measurement of force/deformation. Combining ML and piezoelectricity within a single device provides a comprehensive understanding of mechanical events, providing qualitative and quantitative information about strain‐related phenomena. A ZnS:Cu/polydimethylsiloxane (PDMS) composite and a biocompatible silk fibroin/PDMS composite are prepared to generate ML and electrical signals, respectively. An innovative method for obtaining powder from silk fabrics is employed. The microstructure and composition of silk fibroin powder are also examined via X‐ray diffraction and Fourier Transform Infrared (FTIR) spectroscopy. Mechanical stimuli such as pressure, stretching, twisting, bending, vibration, and rubbing are applied to the device to demonstrate optical and electrical responses. Under pressure, a voltage of 3.82 V and an output current of 201.6 nA are generated at a force of 1 N. Furthermore, a handwritten test is conducted to qualitatively visualize letters based on ML effects and explore the feasibility of using artificial intelligence to classify voltage signals generated during writing into their corresponding letters. This biocompatible, dual‐modal self‐powered sensor demonstrates broad applicability in wearable technology, biomechanics, human–machine interaction, security, and energy harvesting. [ABSTRACT FROM AUTHOR]

This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N'-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber production. The dielectric, piezoelectric, and pyroelectric properties of these fibers were carefully examined. Based on measurements of the dielectric permittivity temperature and frequency dependence, together with the pyroelectric results, a transition from a high temperature paraelectric to a ferroelectric phase that persisted at room temperature was found to occur at 438 K. The measured pyroelectric coefficient yielded values as high as 290 μC K−1 m−2, which is in between the values reported for MDABCO-NH4I3 and the semiorganic ferroelectric triglycine sulfate (TGS). The hybrid nanofibers exhibited good morphological characteristics and demonstrated very good piezoelectric properties. Specifically, a piezoelectric coefficient of 42 pC/N was obtained when applying a periodical force of 3 N and a piezoelectric voltage coefficient of geff = 0.65 V mN−1. The performance of these fibers is on par with that of materials discussed in the existing literature for the fabrication of nano energy-harvesting generators. Importantly, the perovskite nanocrystals within the fibers are protected from degradation by the surrounding polymer, making them a promising environmentally friendly platform for flexible mechanical energy harvesting. [ABSTRACT FROM AUTHOR]

In the human body, non-centrosymmetric biological structures exhibit piezoelectric effect across from microscopic biomolecular building blocks to macroscopic tissues and organs. However, the fabrication of piezoelectric devices from discarded natural tissues and organs has rarely been exploited for energy harvesting applications. Herein, the extracted human teeth were recycled as an active layer in a piezoelectric nanogenerator for power generation. Due to the piezoelectric effect of enamel and dentin, a human teeth-based sandwiched piezoelectric nanogenerator was fabricated, producing high and stable power outputs with an open-circuit voltage of approximately 0.9 V under an external force at 60 N. Furthermore, the high mechanical durability of the piezoelectric nanogenerator was also verified after 1600 pressing-and-releasing cycles without noticeable output degradation. Notably, for the first time, a light-emitting diode (LED) was illuminated by the human teeth-based piezoelectric device. This work exemplifies a sustainable strategy to recycle the extracted human teeth by fabricating a piezoelectric nanogenerator for energy harvesting, providing inspiration for converting waste into wealth toward green energy in bionanotechnology.

Tailoring the surface morphology of nanofibers determines its application to an excessive extent. At present, different structures of nanofibers have been produced such as wrinkled, grooved, porous, rough, etc. Amongst them, wrinkled nanofibers have attracted the attention of researchers due to their exceptional structure and properties such as coarse surface, high surface energy, high specific surface area, excellent mechanical properties, and good piezoelectricity resulting in serving successfully in various fields such as energy harvesting, air filtration, water filtration, gas sensors, biomedical applications, fuel cells, and energy storage. Therefore, this work aims to spotlight the importance of the wrinkled structure, methods, and strategies used for producing electrospun wrinkled nanofibers of various materials. This review focuses on the materials, preparation methods, and applications of the electrospun wrinkled nanofibers. This review can serve as an essential reference for the materials, formation methods, and applications of wrinkled nanofibers prepared via electrospinning. [ABSTRACT FROM AUTHOR]

Flexible and cost‐effective poly(vinylidene fluoride) (PVDF)‐based composites having excellent piezo performance are quite interesting for developing actuators, sensors, and nanogenerators. In this work, a hybrid PVDF‐based nanocomposite consisting of a fixed quantity of titanium dioxide (TiO2) and varying quantities of reduced graphene oxide (rGO) for increased mechanical and piezoelectric performance is reported for the first time. Compared to pure PVDF, there is a significant enhancement in mechanical properties for hybrid nanocomposites. The highest piezoelectric voltage as well as current values of 10.2 V and 0.78 μA are recorded for a hybrid nanocomposite containing 1 wt% of rGO for continuous finger‐tapping operation. A multicriteria decision‐making (MCDM)‐based material selection and optimization technique called TODIM is applied, and a sensitivity study is carried out to select the best material for mechanical energy harvesting applications. A hybrid nanocomposite based on PVDF‐TiO2 with 1% rGO loading is the most suitable material according to the TODIM (an acronym in Portuguese for Interactive Multicriteria Decision Making) approach. Highlights: PVDF‐TiO2‐rGO nanocomposites are fabricated by solvent casting.TODIM optimization technique is applied for the best material selection among samples.Material ranking consistency shows the reliability of the TODIM method.Conductive rGO increases interfacial polarization, resulting in enhanced ε values.An increment of 88% and 104% in tensile strength and elastic modulus, respectively. [ABSTRACT FROM AUTHOR]

In this work, a novel multiscale topology optimization method has been proposed for the design of electromechanical energy-harvesting systems converting mechanical vibrations into electric currents made of non-piezoelectric materials. At the microscopic scale, the material is assumed to be periodic, porous, and flexoelectric, although not piezoelectric. A first step of topology optimization is performed, in order to maximize the effective (homogenized) flexoelectric properties of the material, where a flexoelectric homogenization model is first formulated. As a result, the effective material, although made of a non-piezoelectric material, has apparent piezoelectric properties. In a second step, these properties are used to model the behavior of a dynamic electromechanical energy-harvesting system structure. A second topology optimization step, this time performed at the structural scale, aims to maximize the system electromechanical coupling factor (ECF) for a given forced vibration frequency, including the micro-inertial effect. At both scales, an isogeometric analysis method is employed to solve the strain-gradient problems numerically. We show that the optimized structure obtained offers significant gains in terms of ECF (by a factor of between 2 and 20) compared with non-optimized structures of the same volume, over a wide range of excitation frequencies. The procedure could open up new possibilities in the design of energy recovery systems without the use of piezoelectric materials. [ABSTRACT FROM AUTHOR]

As a promising energy‐harvesting technique, an increasing number of researchers seek to exploit the piezoelectric effect to power electronic devices by harvesting the energy associated with water flow. In this emerging field, a variety of research themes attract interest for investigation; these include selection of the excitation mechanism, oscillation structure, piezoelectric material, power management interface circuit, and application. Since there has been no comprehensive review to date with respect to the harvesting of water flow using piezoelectric materials, herein relevant work in the last 25 years is reviewed. To ensure that key aspects of the water‐flow energy harvester are overviewed, they are discussed in the context of energy‐flow theory, which includes the three stages of energy extraction, energy conversion, and energy transfer. The development of each energy‐flow process is reviewed in detail and combined with meta‐analysis of the published literature. Correlations between the harvesting processes and their contribution to the overall energy‐harvesting performance are illustrated, and directions for future research are also proposed. In this review, a comprehensive understanding of water‐flow piezoelectric energy harvesting is provided and it is aimed to guide future research and the development of piezoelectric harvesters for water‐flow‐powered devices is promoted. [ABSTRACT FROM AUTHOR]

Multilayered flexible piezoelectric energy harvesting devices (FPEDs) are a new future harvesting technology which are highly flexible and lightweight than familiar cantilever piezoelectric energy harvesters. This mechanical vibration driven FPED is a strongly coupled multiphysics phenomena that involve complex natural three-way interaction among the composite piezoelectric structure, the electric charge accumulated in the piezoelectric material, and a controlling electrical circuit attached to it. Efficient and accurate computational solution approaches are essential for analyzing these mechanical vibration-driven FPEDs to capture the main physical aspect of the coupled phenomena and to accurately predict the output voltage. While there are some numerical models for simple familiar cantilever type piezoelectric energy harvester reported in the literature, a fully three-dimensional strongly coupled model for complex material distributed, complex geometry, and multilayered FPED involving strong coupling of structure, piezoelectricity, and circuit phenomena has not yet been developed. A partitioned iterative algorithm is developed using a hierarchical decomposition approach wherein the coupled three fields are solved separately and coupled through loop union integration techniques that provide an efficient and accurate simulation of FPEDs. The simulation results matched the experiment results very well. This study provides a basis for the natural extension of partitioned iterative finite element coupled algorithm to simulate the future piezoelectric energy harvesting technologies involving a strong coupling of structure, piezoelectricity, and circuit phenomenon. [ABSTRACT FROM AUTHOR]

Within the burgeoning field of electronic materials, B−N Lewis acid‐base pairs, distinguished by their partial charge distribution across boron and nitrogen centers, represent an underexplored class with significant potential. These materials exhibit inherent dipoles and are excellent candidates for ferroelectricity. However, the challenge lies in achieving the optimal combination of hard‐soft acid‐base pairs to yield B−N adducts with stable dipoles. Herein, we present an enantiomeric pair of B−N adducts [R/SC6H5CH(CH3)NH2BF3] (R/SMBA‐BF3) crystallizing in the polar monoclinic P21 space group. The ferroelectric measurements on RMBA‐BF3 gave a rectangular P‐E hysteresis loop with a remnant polarization of 7.65 μC cm−2, a value that aligns with the polarization derived from the extensive density‐functional theory computations. The PFM studies on the drop‐casted film of RMBA‐BF3 further corroborate the existence of ferroelectric domains, displaying characteristic amplitude‐bias butterfly and phase‐bias hysteresis loops. The piezoelectric nature of the RMBA‐BF3 was confirmed by its direct piezoelectric coefficient (d33) value of 3.5 pC N−1 for its pellet. The piezoelectric energy harvesting applications on the sandwich devices fabricated from the as‐made crystals of RMBA‐BF3 gave an open circuit voltage (VPP) of 6.2 V. This work thus underscores the untapped potential of B−N adducts in the field of piezoelectric energy harvesting. [ABSTRACT FROM AUTHOR]

In the present study, poling−free PLLA/VB2 piezoelectric composites are fabricated to achieve synchronous sound recognition and energy harvesting. The addition of VB2 can interact with PLLA by intermolecular hydrogen bonding, inducing the dipole orientation of C=O in PLLA. Meanwhile, VB2 can promote crystallization of PLLA through heterogeneous nucleation. The combination of the two strategies significantly improves the piezoelectric performance of PLLA/VB2 composites. The PLLA/VB2 can detect the sound frequency with an accuracy of 0.1% in the range of 0–20 kHz to recognize characteristic sounds from a specific source. PLLA/VB2 can also convert sound into electrical energy synchronously with an energy density of 0.2 W/cm−3 to power up LEDs. Therefore, PLLA/VB2 shows great potential in the field of information and energy synchronous collection. [ABSTRACT FROM AUTHOR]

In order to further improve the performance of 0.94[(Bi0.5Na0.5)TiO3]‐0.06BaTiO3/polyvinylidene fluoride (NBT‐BT/PVDF) flexible composite films prepared by the hot‐pressing method, the effect of surface modification of the NBT‐BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3‐aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) were added to enhance dispersion and interfacial adhesion of the active phase powder with the polymer matrix. The highest amount of the electroactive PVDF β‐phase was formed in APTES‐modified samples while in DDTES samples mainly γ‐phase was formed as shown by Fourier‐transform infrared spectroscopy analysis. Differential scanning calorimetry measurements indicated that the addition of filler particles reduced the total crystallinity degree of the PVDF. Dielectric permittivity values as well as dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES‐modified particles led to enhanced breakdown strength of these samples. The highest level of agglomeration in the DDTES‐modified samples induced the deterioration of ferroelectric properties. The highest voltage output of ~15 V and 225 μW of power was obtained for the APTES‐modified harvester, evidencing their potential for energy harvesting applications. Highlights: Surface of NBT‐BT particles was successfully modified by the silanization method.NBT‐BT‐PVDF flexible lead‐free composite films were prepared by hot pressing.APTES coupling agent enabled the transformation of PVDF α‐phase into electro‐active β.APTES‐modified samples showed the highest breakdown strength.Notable properties for energy harvesting application found, up to 225 μW of generated power. [ABSTRACT FROM AUTHOR]

This work aims at coupling computational fluid dynamics (CFD) and modal analysis (FEM) to simulate energy harvesting of wind loads to produce electrical energy by piezoelectric effect. To complement this objective, CFD-FEM simulation was performed by means of SolidWorks® 2021 add-ins, starting from the generation of the virtual model, computational domain definition, and imposition of wind loads, boundary conditions, and model discretization, by means of a mesh comprising a total of 84 709 nodes and 50 157 high order quadratic elements of 1 mm size and finally a mesh calibration was performed. The results showed that the section near the clamping base concentrated the highest pressures, regardless of the simulated velocity (3 to 21 m/s). The maximum velocity caused a pressure over the impact zone of 101 716 Pa, a relative pressure of 391.75 Pa, and shear stress of 4.78 Pa. The natural frequencies of vibration using the CFD output, range from 69 to 99 Hz. The direction of wind action is defined as the direction of piezoelectric placement, specifically near the base where the maximum effective voltage output (6.79 V) is obtained which, with an external resistance of 10 and 20 MO, produces an electrical power of 4.62 and 2.31 µW, respectively. [ABSTRACT FROM AUTHOR]

The development of small-scale and low power consumption devices has been motivating the design of intelligent mechanisms, exhibiting a wide power density spectrum across various external sources. Smart materials come up as an attractive alternative due to their intrinsic multi-coupling between different physical domains. In this context, piezoelectric materials allow conversion of mechanical energy of movement into electrical power through the direct piezoelectric effect. This work investigates a piezoelectric energy harvester combined with a shape memory alloy (SMA) spring to explore the combination of both the smart materials for energy harvesting. The pseudoelastic hysteretic effect of SMA is explored in order to passively change the internal system properties such as stiffness and damping during the harvesting process. Numerical analyses are performed considering the normalized power converted by the harvester, focusing on the influence of the SMA martensite phase transformation under different scenarios. The results exhibit an increment in the harvester bandwidth when compared with a traditional linear piezoelectric energy harvester. [ABSTRACT FROM AUTHOR]

High β-phase polyvinylidene fluoride (PVDF) thin films have excellent piezoelectricity and flexibility. They are widely used in wearable devices, hydroacoustic ultrasound, and energy harvesting. The preparation of PVDF thin films by near-electric-field 3D printing can be customized in shape, and the high β-phase can be obtained without stretching or polarization. In this work, the effects of polar solvent, printing voltage, and PVDF molecules on the β-phase content of PVDF thin films prepared by near-electric-field 3D printing were analyzed. The results show that the polarity of the solvent affects the molecular chain conformation of PVDF, which is favorable for the generation of the β-phase. With the increase of solvent polarity, the β-phase content in PVDF films increased from 21.40% to 26.31%. The mutual motion of the collecting plate and the needle will produce stronger mechanical traction on the PVDF fibers, which is due to the smaller diameter of the PVDF fibers caused by the high printing voltage. The joint action of this tensile force and the strong electric field attraction promotes the β-phase transition. When the printing voltage is 8 kV, the F(β) value of PVDF film is increased by 47.37% over that without applied voltage. In addition, the interaction of small and large PVDF molecular weight will also result in mechanical deformation of the molecular chain and promote the β-phase transition. [ABSTRACT FROM AUTHOR]

The development of high-performance lead-free K0.5Na0.5NbO3-based piezoceramics for replacing commercial lead-containing counterparts is crucial for achieving environmentally sustainable society. Although the proposed new phase boundaries (NPB) can effectively improve the piezoelectricity of KNN-based ceramics, the difficulty of achieving saturated poling and the underlying multiscale structures resolution of their complex microstructures are urgent issues. Here, we employ a medium entropy strategy to design NPB and utilize texture engineering to induce crystal orientation. The developed K0.5Na0.5NbO3-based ceramics enjoys both prominent piezoelectric performance and satisfactory Curie temperature, thus exhibiting an ultrahigh energy harvesting performance as well as excellent transducer performance, which is highly competitive in both lead-free and lead-based piezoceramics. Comprehensive structural analysis have ascertained that the field-induced efficient multiscale polarization configurations irreversible transitions greatly encourages high saturated poling. This study demonstrates a strategy for designing high-performance piezoceramics and establishes a close correlation between the piezoelectricty and the underlying multiscale structures. There are difficulty of achieving saturated poling and understanding of multi-scale structures in (K, Na)NbO3 ceramics. Here, the authors find atomic-scale polymorphic distortion and micrometer-scale high-density thin striped domains, which is key for high saturated poling. [ABSTRACT FROM AUTHOR]

Electromechanically converted piezoelectric materials have great applications in actuators, sensors, and energy harvesters. Organic piezoelectric materials are environmentally friendly, easy to prepare, and have a low molecular mass compared to conventional inorganic piezoelectric materials. Here, we present an organic hydrogen bonding piezoelectric material, lamivudine hydrate, which crystallized in the P21 space group at room temperature and exhibits a decent d33 value of 21 pC N−1. This value is comparable to that of the commercial piezoelectric material, Tri‐Glycine Sulfate (TGS, d33=22 pC N−1). Moreover, lamivudine hydrate possesses a superior g33 value of 826×10−3 V m N−1, which is much higher than that of commercial TGS and most of the piezoelectric ceramics. While the lamivudine crystal was refined in the P43212 space group, showing no piezoelectric activity. The presence of crystalline water plays a crucial role in establishing its polar structure and achieving high piezoelectric properties of lamivudine hydrate crystal. The decent d33 and g33 values make it a promising candidate for advanced materials in high‐performance piezoelectric sensors, particularly in applications involving flexible, wearable, and biomechanical devices. [ABSTRACT FROM AUTHOR]

Electrospinning (ES) methods that can produce piezoelectricity in polymer nanofibers have attracted tremendous research attention. These electrospun polymer nanofibers can be employed for sensors, energy harvesting, tissue engineering, and filtration applications. This paper reviews the performance of a variety of electrospun piezoelectric polymer nanofibers produced by different ES methods, including near‐field electrospinning and conventional far‐field electrospinning methods. Herein, it is described how the ES method can affect the piezoelectric properties of various polymer nanofibers, including poly(vinylidene difluorine), poly(vinylidene fluoride‐trifluoroethylene), nylon 11, poly(l‐lactic acid), and poly(α‐benzyl‐l‐glutamate). Due to the varied matrix structures of piezoelectric polymer nanofibers, the ES method may conduct variable effects on the piezoelectric properties of polymer nanofibers. After characterizations by X‐ray diffraction, Fourier transform infrared spectrum, dielectric spectra, and piezoelectric coefficient measurements, it is found that the piezoelectric properties of the polymer nanofibers can be significantly affected by the ES parameters. Most of previous review articles focus on the output performance of electrospun polymer nanofibers. A detailed description of how different ES methods affect the piezoelectricity of polymer nanofibers is still lacking. In this review paper, the basic principle behind ES methods and the way in which different ES methods affect the properties of polymer nanofibers are examined. [ABSTRACT FROM AUTHOR]

Piezoelectricity refers to the ability of certain materials to generate electric charges when subjected to mechanical stress or strain, and vice versa. This phenomenon has been widely studied in inorganic materials, such as quartz and ceramics, and has found numerous applications in sensing, actuation, and energy harvesting. There has been a growing interest in piezoelectricity for polymeric materials that are lightweight, flexible, and highly processable for a wide range of applications, including sensors for environmental and biomedical monitoring, energy conversion from mechanical vibrations, and actuation in soft robotics. However, characterizing the piezoelectric tendency of polymeric materials tends to be a complex and challenging process, as the effect is often weak and dependent upon various factors including material structure, processing conditions, and measurement setup. While many past and current review articles have covered theories and principles associated with piezoelectric polymers to some extent, detailed information on the corresponding experimental techniques used to measure their piezoelectric properties remains limited. This mini‐review paper aims to consolidate and summarize various approaches, including quasi‐static methods, optical interferometry, dielectric spectroscopy, and piezoelectric force microscopy, and to provide insights into the principles, advantages, limitations, and challenges associated with these techniques. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]