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This work investigates the physical properties of Al1−xScxN thin films sputtered at low temperatures by varying the process conditions. Specifically, the films were deposited at room temperature by applying a radio frequency power equal to 150 W to an AlSc alloy (60:40) target, varying the nitrogen flux percentage in the (Ar + N2) sputtering atmosphere (30%, 40%, 50%, and 60%) and keeping constant the working pressure at 5 × 10−3 mbar. The structural and chemical properties of the Al1−xScxN films were studied by x-ray diffraction and Rutherford backscattering spectrometry techniques, respectively. The piezoelectric response was investigated by piezoresponse force microscopy. In addition, the surface potential was evaluated for the first time for Sc-doped AlN thin films by Kelvin probe force microscopy, providing piezoelectric coefficients free from the no-piezoelectric additional effect to the mechanical deformation, i.e., the electrostatic force. By alloying AlN with scandium, the piezoelectric response was strongly enhanced (up to 200% compared to undoped AlN), despite the low deposition temperature and the absence of any other additional energy source supplied to the adatoms during thin film growth, which generally promotes a better structural arrangement of polycrystalline film. This is a strategic result in the field of microelectromechanical systems completely fabricated at low temperatures. [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric properties of chemical solution deposition derived ferroelectric HfO2–CeO2 thin films deposited on platinized silicon substrates are investigated. Large-signal strain-field measurements show an effective piezoelectric coefficient of approximately d 33 , eff = 12.7 pm / V for 17 mol. % cerium under bipolar excitation and d 33 , eff = 8 pm / V under unipolar excitation. Progressive bipolar electric field cycling leads to a reduction in the overall field induced strain although no fatigue with regards to the polarization is observed. To explain this, we propose a model explanation based on changes in the polarization reversal pathway from a primarily ferroelastic, i.e., 90 ° domain wall mediated switching, to a 180 ° type switching. Furthermore, unipolar strain-field measurements reveal a negative intrinsic piezoelectric coefficient in the absence of any ferroelastic contribution, confirming theoretical predictions. The results suggest that the ferroelastic contribution to the field-induced strain needs to be stabilized in Hafnia-based ferroelectric materials to make them more feasible for micro-electromechanical systems. [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]

The exploration of energy harvesting encompasses a wide array of sources, with a specific focus on recovering mechanical and magnetic energy from overlooked outlets, driving current research endeavours. In this study, we developed highly flexible Magneto-Mechano-Electric (MME) harvesters by combining poly(vinylidene fluoride) (PVDF)/barium calcium zirconium titanate (BCT-BZT) composite films with metglas. The flexible piezoelectric polymer-ceramic composite films were fabricated using a solvent casting technique. The high piezoelectric BCT-BZT fillers were synthesized through a sol-gel reaction route. A thorough analysis was carried out on these composites to evaluate their structural, functional, microstructural, and dielectric properties. The composite film loaded with 20 wt% BCT-BZT filler achieved a 78 % β-phase with a significant enhancement in the dielectric properties, resulting in a high permittivity∼40 and low dielectric loss. Employing these films, we engineered nanogenerators capable of converting mechanical energy into electrical energy, yielding an output voltage of 11 V. Thereafter, to harvest mechanical and stray magnetic fields, we developed a MME generator comprising a magnetic Metglas layer and PVDF-BCT-BZT composite and achieved an output voltage of 3.3 V with a power density of 85 μW/m2 when subjected to an AC magnetic field of 5 Oe. Furthermore, the MME generator has demonstrated the ability to charge various capacitors showcasing its potential for usage in self-powered, non-contact, and implantable devices. [ABSTRACT FROM AUTHOR]

Flexible high-performance piezoelectric nanogenerator (PENG) excel in converting mechanical energy into electrical energy and exhibit remarkable sensitivity, a feature that is paramount for the development of self-driven piezoelectric sensors. In this study, electrospinning technology was used to prepare poly (vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] based piezoelectric nanofiber composite films containing potassium-sodium niobate nano particles (KNN NPs) and Nb 2 CT x co-doping, as well as single-component doping. The co-doped composite film attained an optimal β-phase content of 91.33%. Owing to the enhanced dipole alignment and interface charge polarization, the piezoelectric performance of the co-doped composite film was significantly enhanced compared to that of single-component doping. The co-doped piezoelectric composite film displayed a stable maximum output voltage of 20 V and an output current of 1.46 μA. The peak instantaneous power output was measured at 9.9 μW under the optimal resistive load of 10 MΩ. Durability testing over 2000 cycles affirmed the excellent mechanical stability of the piezoelectric composite film. Moreover, the fabricated piezoelectric composite film showed considerable potential in applications such as monitoring human activities and serving as an early warning system for natural disasters such as landslides, as indicated by the test results. [ABSTRACT FROM AUTHOR]

The demand for high-performance electromechanical resonators is ever-growing across diverse applications, ranging from sensing and time-keeping to advanced communication devices. Among the electromechanical materials being explored, thin-film lithium niobate stands out due to its strong piezoelectric properties and low acoustic loss. However, in nearly all existing lithium niobate electromechanical devices, the configuration is such that the electrodes are in direct contact with the mechanical resonator. This configuration introduces an undesirable mass-loading effect, producing spurious modes and additional damping. Here, we present an electromechanical platform that mitigates this challenge by leveraging a flip-chip bonding technique to separate the electrodes from the mechanical resonator. By offloading the electrodes from the resonator, our approach yields a substantial increase in the quality factor of these resonators, paving the way for enhanced performance and reliability for their device applications. [ABSTRACT FROM AUTHOR]

This study provides insights into the design and analysis of surface acoustic wave sensors customized for detecting volatile organic compounds (VOCs), utilizing an innovative AlN/diamond/Si multilayered configuration. The results are explored numerically using finite element method simulation within the COMSOL Multiphysics package. The potential of the AlN piezoelectric thin film on diamond on Si substrates for sensor development is examined. The phase velocities, electromechanical coupling coefficient, K 2 , and reflectivity are examined versus the normalized thicknesses of the substrates, considering both Rayleigh and Sezawa wave modes. Additionally, the temperature coefficient of frequency (TCF) is investigated. The results show that the TCF increases with reducing the thickness of the diamond. For instance, at khAIN = 2 where the maximum K 2 can be observed, the TCF increases from −17 to −14 to 3 ppm/°C for khdiamond = 0.5, 0.2, and 0.05, respectively. Furthermore, the sensor sensitivity to gas concentration in the air is examined for several VOCs using a thin polyisobutylene (PIB) layer for sensor demonstration. The study shows a remarkable sensitivity enhancement in sensor sensitivity achieved through the Sezawa wave mode compared to the Rayleigh counterpart. For example, in the case of tetrachloroethene gas (PCE), the sensor sensitivity reaches 197.73 Hz/ppm for the Sezawa mode, as opposed to 62.15 Hz/ppm for the Rayleigh mode. [ABSTRACT FROM AUTHOR]

In this paper, we describe the fracture mechanisms of lead zirconate titanate (PZT) piezoelectric thin films synthesized by sol-gel processing. One of the technical concerns in piezoelectric thin films is how their surface fractures because, in most cases, the films fail electrically, and the fracture surface is remade after its first fracture. To estimate the failure mechanisms, cantilever-type and clamped capacitor-type actuators made of PZT piezoelectric thin films deposited on a Si wafer were prepared and subjected to electrical and mechanical stresses. The cantilever-type actuators showed a decreasing trend in dielectric withstand voltage with increasing number of mechanical loading cycles. The clamped capacitor-type actuators showed a decreasing trend in withstand voltage with increasing cyclic voltage amplitude. Through mechanical and electrical experiments, we found that the origin of cracking differed from that of short circuit. This finding indicates that the PZT films fractured mechanically, then fractured electrically. The focused ion beam fabrication of a surface defect and scanning electron microscopy observation around the defect suggest a reasonable fracture mechanism. [ABSTRACT FROM AUTHOR]

Knowledge of the thermodynamic equilibria and domain structures of ferroelectrics is critical to establishing their structure–property relationships that underpin their applications from piezoelectric devices to nonlinear optics. Here, we establish the strain condition for strain phase separation and polydomain formation and analytically predict the corresponding domain volume fractions and wall orientations of, relatively low symmetry and theoretically more challenging, monoclinic ferroelectric thin films by integrating thermodynamics of ferroelectrics, strain phase equilibria theory, microelasticity, and phase‐field method. Using monoclinic KxNa1 − xNbO3(0.5 < x < 1.0) thin films as a model system, we establish the polydomain strain–strain phase diagrams, from which we identify two types of monoclinic polydomain structures. The analytically predicted strain conditions of formation, domain volume fractions, and domain wall orientations for the two polydomain structures are consistent with phase‐field simulations and in good agreement with experimental results in the literature. The present study demonstrates a general, powerful analytical theoretical framework to predict the strain phase equilibria and domain wall orientations of polydomain structures applicable to both high‐ and low‐symmetry ferroelectrics and provide fundamental insights into the equilibrium domain structures of ferroelectric KxNa1 − xNbO3 thin films that are of technology relevance for lead‐free dielectric and piezoelectric applications. [ABSTRACT FROM AUTHOR]

Studying the electromechanical response behavior of piezoelectric thin films under different loading conditions is of great value for the development and optimization of piezoelectric sensors and flexible portable electronic devices. This paper establishes the theory of large deflection vibration of rectangular four-edge simply supported piezoelectric thin films using the energy method, and analyzes the electromechanical response characteristics of vibration force (including resonant frequency and nonlinear vibration). Meanwhile, the electromechanical response behavior of Poly(vinylidene fluoride) (PVDF) films under different loading conditions (static and harmonic vibration) is analyzed. The study investigates the nonlinear vibration characteristics and resonance frequency variations under different film sizes and thickness conditions in the case of various loading conditions. The developed model can predict the resonance frequency associated with the plate dimensions. This study is of great significance for the research and application of laminated piezoelectric film sensors. [ABSTRACT FROM AUTHOR]

Flexible electronic components such as wearable sensors, energy harvesting devices, and human health monitoring systems based on piezoelectric materials have garnered significant attention within the scientific community. In this study, PZT nanofibers were modified with dopamine hydrochloride prior to their integration into PVDF fibers, serving as piezoelectric reinforcements to enhance the mechanical and piezoelectric characteristics of composite fiber films. Subsequently, a facile hot-pressing method was employed to fabricate multilayered films characterized by a densely packed surface fiber arrangement and a loosely organized internal fiber orientation, which markedly improved the self-supporting ability and fiber density of the electrospun fiber films. A detailed investigation into the micro-morphology, crystallinity, and enhanced piezoelectric properties of the films was conducted. Notably, the composite fiber film containing 6 wt% PZT NFs exhibited a peak piezoelectric coefficient (d 33) of 29 pC/N, resulting in an output voltage of 13.8 V. This represents a 2.23-fold enhancement in d 33 value and a 4.6-fold increase in output voltage when compared to the pristine PVDF fiber film, which had a d 33 of 13 pC/N and an output voltage of 3 V. The power density achieved by the sensor is 0.73 μW/cm2. This performance is underpinned by a high piezoelectric coefficient, outstanding output characteristics, and robust stability, which collectively enhance the sensor's efficacy in various applications. This research presents an effective approach for augmenting the piezoelectric performance of PVDF-based composite films and paves the way for the advancement of piezoelectric energy harvesting applications. [ABSTRACT FROM AUTHOR]

Exploring the unique physical properties of oxide perovskites necessitates their growth on diverse single‐crystal substrates. The thin‐film growth of perovskite SrMnO3 (SMO) has been a particular focus of research due to its emerging room‐temperature multiferroicity. Herein, the epitaxial thin films of (110)‐oriented SMO are grown on the piezoelectric (110)‐oriented (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN‐PT) substrate. The effects of the thickness and oxygen annealing on the crystal structure, stoichiometry, and ferroelectric properties of the SMO thin film are systematically investigated. The tensile strain produced by the lattice mismatch between the bulk SMO and the PMN‐PT substrate causes an expansion of the c‐lattice parallel to the in‐plane direction of the substrate. The films show larger a‐, b‐, and c‐lattice parameters than the bulk material, resulting in volume expansion of the unit cell. This lattice expansion is attributed to the generation of oxygen vacancies driven by the reduced formation energy caused by the high elastic strain. Piezoelectric force microscopy reveals that the SMO film contains domains with strain‐mediated in‐plane and vacancy‐mediated out‐of‐plane polarization. Furthermore, the piezoelectric response of the PMN‐PT substrate effectively modulates the biaxial tensile strain in the SMO film, offering a potential strategy for controlling the crystal structure and ferroelectric properties of SMO. [ABSTRACT FROM AUTHOR]

[Display omitted] Conventional piezoelectric nanogenerators (PNGs) face challenges in terms of degradation and reusability, which have negative environmental implications. On the other hand, biocompatible and degradable piezoelectric materials often exhibit lower piezoelectric response. In this study, potassium sodium niobate (KNN) powder and the biodegradable polymer poly(ε-caprolactone) (PCL) were used to fabricate piezoelectric composite films through solution casting. By constructing staggered electrodes, the total polarized charges quantity is increased, achieving a larger current output. The three-unit PNG (3-PNG) based on the composite film with 15 wt% KNN powder, reaches a maximum output current of 0.85 μA, which exhibits higher charging efficiency compared to 1-PNG. Moreover, the prepared 3-PNG can effectively harvest mechanical energy from human activities and maintain a stable output after 10,000 cycles of bending and releasing. The film exhibits complete degradation when exposed to acidic, neutral, and alkaline solutions. This research provides a promising option for environmentally friendly piezoelectric materials selected and output performance enhanced through optimized structural designs, making them more suitable for practical applications. [ABSTRACT FROM AUTHOR]

Piezoelectric thin films have been widely used in electro-acoustic devices including ones measuring Rayleigh wave speed. The main objective of this work is to find an explicit formula of Rayleigh speed taking into account the effect of the thin piezoelectric film. First the problem of Rayleigh surface waves propagating along an orthotropic substrate coated by a thin piezoelectric film is considered using Stroh's formalism approach. Then, the exact secular equation of Rayleigh wave is obtained in implicit form. In case when the thickness of the thin layer is much smaller than the considering wavelength of Rayleigh waves, an asymptotic formula of Rayleigh speed is derived from the asymptotic form of the exact secular equation. The obtained asymptotic formula is simple enough and could be used in practice when Rayleigh speed is measured by using piezoelectric device. Numerical illustrations are carried out to show the validity of the obtained approximate formulas and its potential application in inverse problem. [ABSTRACT FROM AUTHOR]

In piezoelectric catalysis, the interaction between reaction molecules and the catalyst surface is of great significance for designing highly selective reaction processes. In this study, chemically functionalized BaTiO 3 nanoparticles were fabricated using the hydrothermal method, and the piezoelectric catalytic activity was evaluated for degradation dye reactants by ultrasonic vibration. Due to surface modification of BaTiO 3 nanoparticles, the carboxyl groups will be applied on the surface of BaTiO 3 nanoparticles, resulting in the reduction in particle size and an increase in specific surface area. The adsorption of the carboxyl groups on the surface can also improve the ability of the BaTiO 3 nanoparticles to capture the organic dyes. A high piezoelectric catalytic reaction rate constant of 0.0716 min−1, together with a degradation efficiency of >90 % was achieved within 30 min under 60 kHz and 100 W ultrasonic conditions. These results show that the surface modification of BaTiO 3 nanoparticles brought excellent performance of piezoelectric catalysis by controlling the precursor and hydrothermal parameters. This study provides a new method for the preparation of chemically functionalized piezoelectric catalysts and design of other new highly selective catalysts. [ABSTRACT FROM AUTHOR]

In this paper, a novel flexible piezoelectric thick-film generator is proposed to address the challenges caused by flexible deformation and high piezoelectricity. This improves the output charge of the generator, which breaks the limitation imposed by the rigid and brittle nature of traditional piezoelectric bulks on elastic strain and piezoelectric performance. Additionally, the low piezoelectric coefficient of piezoelectric polymer-based piezoelectric generators is also resolved. Given the high thickness precision of electrohydrodynamic jet printing technology, the facile production of 10-μm thick film components is achieved through a process of printing and layer-by-layer accumulation on a flexible substrate, which ensures the flexible deformation and piezoelectric characteristics of the functional film. To ensure that AC is converted into stable DC output, a bipolar charge collection circuit is developed. The printed thick film produces an excellent performance in surface uniformity and smoothness. Notably, the piezoelectric constant d 33 is measured to be approximately 80 pC/N, which is five times higher than the d 33 value of flexible PVDF films. Additionally, the strength of adhesion between the printed thick film and the flexible substrate is remarkably high, reaching up to 20 N, which is an order of magnitude higher than the magnetron sputtering method. In a single cycle, the forward charge output reaches an impressively high level of 260 nC, which is approximately thirteen times the charge transfer capability of PVDF flexible generator. Furthermore, a bipolar charge collection circuit is applied to convert AC into DC effectively. This increases the output voltage from 2 V to 4 V. The illumination of commercial electronic screens and 39 LED lights demonstrates the applicability of micron-scale jet-printed thick films in micro-energy harvesting. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have become a key component in sensors and actuators in many industrial fields, such as energy harvesting devices, self-powered structures, biomedical devices, nondestructive testing, owing to the novel properties including high piezoelectric coefficient and electromechanical coupling factors. Piezoelectric thin films integrated on silicon substrates are widely investigated for their high performance and low manufacturing costs to meet the requirement of sensor networks in internet of things (IoT). The aim of this work is to clarify the application and design structure of various piezoelectric thin films types, synthesis methods, and device processes. Based on latest literature, the process of fabricating thin film sensors is outlined, followed by a concise overview of techniques used in microelectromechanical systems (MEMS) processing that can integrate more complex functions to obtain relevant information in surrounding environment. Additionally, by addressing piezoelectric thin films sensors as a cutting-edge technology with the ability to produce self-powered electronic devices, this work delivers incisive conclusions on all aspects of piezoelectric sensor related features. A greater understanding of piezoelectricity is necessary regarding the future development and industry challenges. [ABSTRACT FROM AUTHOR]

This document is a corrigendum for an article titled "Recent progress in piezoelectric thin films as self-powered devices: material and application." The corrigendum addresses errors in the references and their citations in the published article. It provides the correct references for several studies related to AlN and PZT piezoelectric films. The corrigendum aims to rectify the inaccuracies in the original article and ensure the accuracy of the references cited. [Extracted from the article]

Bismuth ferrite (BiFeO3, BFO) is one of the few single-phase crystalline compounds exhibiting strong multiferroic properties at room temperature, which makes it promising for use in various fields of science and technology. The remarkable characteristics of BFO at the nanoscale position it as a compelling candidate for enhancing the functionalities of polymeric nanocomposite materials. In this study, we explore the fabrication of polyvinylidene fluoride (PVDF) nanocomposites with a variable content of BFO nanopowders (0, 5, 10, 15, 20, and 25 wt%) by solution casting in the form of thin films with the thickness of ~60 µm. Our findings reveal that the presence of BFO nanoparticles slightly facilitates the formation of β- and γ-phases of PVDF, known for their enhanced piezoelectric properties, thereby potentially expanding the utility of PVDF-based materials in sensors, actuators, and energy harvesting devices. On the other hand, the increase in filler concentration leads to enlarged spherulite diameter and porosity of PVDF, as well as an increase in filler content above 20 wt% resulting in a decrease in the degree of crystallinity. The structural changes in the surface were found to increase the hydrophobicity of the nanocomposite surface. Magnetometry indicates that the magnetic properties of nanocomposite are influenced by the BFO nanoparticle content with the saturation magnetization at ~295 K ranging from ~0.08 emu/g to ~0.8 emu/g for samples with the lowest and higher BFO content, respectively. [ABSTRACT FROM AUTHOR]

Flexible bending sensors are crucial components of flexible/wearable electronics. However, their broad application is restricted by their difficulty in sensing different bending directions and, more importantly, their significant output attenuation after long cycles. Herein, a new design of an All‐in‐One piezoelectric bending sensor is proposed, in which double‐deck, cross‐over 3D interdigital microelectrodes (silver nanowires (Ag NWs)) are embedded in a piezoelectric polymer film (poly(vinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE))). The piezoelectric film with the embedded 3D microelectrodes exhibits a high anisotropy coefficient (η90∘${{\eta }_{90^\circ }}$ > 1) based on dual piezoelectric modes (d31 and d33), which renders it more sensitive to different bending directions. More importantly, the homogeneous interconnected interface and heterogeneous microinterlocked interface formed inside the sensor significantly enhance its interface mechanical properties, with at least a tensile strength of 51 MPa, a shear strength of 28 MPa, and an interfacial toughness of 300 J m−2, which are nearly two orders of magnitude greater than those of conventional sandwich architectures. The prepared All‐in‐One sensor shows an extremely stable piezoelectric output over as many as 16 00 000 bending cycles, which represents a remarkable breakthrough. Furthermore, a single sensor can be used to remotely control the multidirectional motion of a smart car, demonstrating enormous potential in practical applications. [ABSTRACT FROM AUTHOR]

Increasing prevalence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) constitutes an emerging water safety issue globally. However, the effectiveness of current water treatment techniques in the control of ARGs dissemination remains controversial. Here, we develop a dual-zone strategy based on piezoelectric membrane filtration to efficiently eliminate waterborne antibiotic resistance. Following complete ARB inactivation and effective ARGs reduction in the retentate near the membrane surface (zone 1), a subsequent trans-membrane process (zone 2) further promotes ARGs elimination in the permeate, due to boosted interactions between ARGs and reactive oxygen species (ROS) generated from piezoelectric peroxymonosulfate activation and minimized ROS competition from inactivated ARB within piezocatalytic channels. The abundance of ARGs was largely reduced to ~1.0 × 103 copies·mL−1 in the permeate from ~5.0 × 106 copies·mL−1 in the feed solution. The singlet oxygen (1O2) is demonstrated to be primarily responsible for ARB inactivation, while 1O2, hydroxyl radical (•OH), sulfate radical (SO4·−) and superoxide radical (·O2−) can all participate in ARGs degradation. Our work demonstrates that the piezoelectric membrane-based dual-zone strategy has great potential to control the risk of ARGs dissemination. [ABSTRACT FROM AUTHOR]

The demand for self‐powered sensing technology and energy harvesting system necessitates high‐performance and flexible piezoelectric materials. This paper presents a novel approach utilizing coaxial electrospinning to fabricate all‐organic PVDF/PMMA piezoelectric fiber films with a shell–core structure. The resulting fiber films, cut into 2 × 2 cm2 square pieces and hot‐pressed every three pieces, demonstrate enhanced piezoelectric properties while retaining high flexibility. The interaction between the CO bonds in the PMMA polymer and the CH2 in PVDF promotes the arrangement of F atoms in PVDF, enhancing the content of the piezoelectric active phase. Additionally, the coaxial electrospinning process fosters vertically oriented hydrogen bonds between PVDF and PMMA, augmenting cross‐linking and improving mechanical properties. Notably, when the PVDF to PMMA layer volume ratio is 5:1, the piezoelectric coefficient (|d33|) of the composite fiber film exhibits a significant 60% increase from 10 pC N−1 in neat PVDF to 16 pC N−1. This research holds substantial promise for applications in self‐powered sensing and energy harvesting piezoelectric materials. [ABSTRACT FROM AUTHOR]

In this study, a highly efficient, sensitive, and lightweight piezoelectric nanogenerator (PENG) is developed using graphene nanoribbons (GNRs) incorporated into the polyvinylidene fluoride (PVDF) matrix. Unzipping multi‐walled carbon nanotubes is an effective and scalable strategy for synthesizing graphene nanoribbons. The synthesized GNRs are employed to prepare nanometer‐scale piezoelectric polymer composite films showing higher piezoelectric performance than neat PVDF. The impact of GNR concentration in the PVDF matrix on the electroactive phase content and piezoelectric properties of the composites is systematically investigated. X‐ray diffraction (XRD) and Fourier‐transformed infrared spectroscopy (FT‐IR) analysis demonstrate an increase in the electroactive β and γ phases of PVDF by incorporating GNRs in the composites. With the optimized concentration of GNRs (1 wt%), the fabricated piezoelectric device can generate open‐circuit voltage and an output power density of 26 V and 16.52 µWcm2, respectively. It is also found that the PVDF‐GNR 1 nanogenerator can be used to generate electrical power by converting mechanical energy from different human activities such as wrist bending, palm tapping, and toe tapping. The findings indicate that (PVDF‐GNR 1) PENG can be applied in self‐powered portable and wearable electronic devices. [ABSTRACT FROM AUTHOR]

Lead based bulk piezoelectric materials, e.g., PbZrxTi1‐xO3 (PZT), are widely used in electromechanical applications, sensors, and transducers, for which optimally performing thin films are needed. The results of a multi‐domain Landau–Ginzberg‐Devonshire model applicable to clamped ferroelectric thin films are used to predict the lattice symmetry and properties of clamped PZT thin films on different substrates. Guided by the thermal strain phase diagrams that are produced by this model, experimentally structural transitions are observed. These can be related to changes of the piezoelectric properties in PZT(x = 0.6) thin films that are grown on CaF2, SrTiO3 (STO) and 70% PbMg1/3Nb2/3O3‐30% PbTiO3 (PMN‐PT) substrates by pulsed laser deposition. Through temperature en field dependent in situ X‐ray reciprocal space mapping (RSMs) and piezoelectric force microscopy (PFM), the low symmetry monoclinic phase and polarization rotation are observed in the film on STO and can be linked to the measured enhanced properties. The study identifies a monoclinic ‐rhombohedral MC‐MA‐R crystal symmetry path as the polarization rotation mechanism. The films on CaF2 and PMN‐PT remain in the same symmetry phase up to the ferroelectric‐paraelectric phase transition, as predicted. These results support the validity of the multi‐domain model which provides the possibility to predict the behavior of clamped, piezoelectric PZT thin films, and design films with enhanced properties. [ABSTRACT FROM AUTHOR]

Advancements in wearable electronics and Internet of Things (IoT) sensors have catalyzed the need for effective micro‐energy harvesting. Piezoelectric nanogenerators (PENGs) are ideal due to their high conversion efficiency and durability. However, the contrast between the high piezoelectric coefficients of brittle inorganic ceramics and the lower coefficients of superior flexibility and biocompatibility of organic polymers poses a significant challenge. This work introduces a novel multilayer composite PENG, integrating a single‐crystal BaTiO3 (BTO) film between poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) layers. The PVDF‐TrFE/BTO/PVDF‐TrFE PENGs demonstrate substantially improved energy harvesting performance, with outputs reaching up to 15.1 V, 2.39 µA, and power density of 17.33 µW cm−2 during bending deformation. This power density represents a significant increase compared to pure PVDF‐TrFE and nanoparticle BTO‐doped PVDF‐TrFE PENGs. Durability tests show consistent performance, with a stable ∼15.0 V output across 2000 bending cycles. Additionally, when attached to the human body, these PENGs efficiently convert body motions into electrical responses. This work demonstrates a significant enhancement in the performance of PENGs using sandwich‐structured composite of PVDF‐TrFE and freestanding single‐crystal BTO films, showing its potential to address the power requirements of wearable and flexible electronic devices. [ABSTRACT FROM AUTHOR]

The amelioration of atomically thin ferroelectric materials is imperative for next‐generation outperformed two‐dimensional (2D) electronics, which is elusive by their bulk counterparts. These remarkable materials' ferroelectric and piezoelectric features are the fundamental urges in optoelectronics, electronics, and energy harvesting. In this work, 2D ferroelectric Bi2O2Se flakes have been synthesized using a modified chemical vapor deposition technique. The 6 nm thick Bi2O2Se flake provides a robust ferroelectric switching under an applied voltage of ±10 V by piezoresponse force microscopy, further confirmed by first principles. Leveraging the successful growth, the high‐quality Bi2O2Se flakes permit the fabrication of a field‐effect transistor (FET) with state‐of‐the‐art performance. The FET device rewards a high current on–off ratio of 108 and field effect mobility of almost 131 cm2 V−1 s−1, owing to the small carrier effective mass of 0.2 m0. Combined, the electric field‐induced local polarization of ferroelectric switching and unprecedented device performance of Bi2O2Se semiconductors are certified for their utilization in advanced nanoelectronics and miniaturization of multifunctional devices with multifunctionalities. [ABSTRACT FROM AUTHOR]

In the quaternary system PbTiO3-PbZrO3-SrTiO3-SrZrO3, compositions that lie close to the antiferroelectric tetragonal and ferroelectric rhombohedral (AFET-FER) phase boundary have potential applications in micro-actuators. However, in thin films, this phase boundary is reported to shift significantly to the zirconium-rich region. Hence, it is necessary to seek alternative approaches to stabilize the tetragonal AFE phase in such compositions. Therefore, this study explores the effect of B-site Mn3+-doping on their structure. Dielectric, ferroelectric, and piezoelectric characteristics of such thin films have been compared with those with increasing Zr/Ti ratios to understand the efficacy of this approach. Transverse piezoelectric coefficient, e31,f, and bipolar strain are found to be higher in Mn3+-doped thin films. Furthermore, large strains and e31,f in thin films have been correlated with structural modifications revealed by systematic Raman spectroscopic investigations. [ABSTRACT FROM AUTHOR]

Piezoelectric thin films are particularly difficult to model at the grain scale. Moreover, this problem is sparsely experimentally documented due to the lack of adequate methods. Here, an original methodology is proposed to study the behavior of single grains during in situ biasing. Pb(Zr,Ti)O3 films have been evaluated thanks to an in situ biasing x-ray diffraction technique performed on a synchrotron source with a sub-micronic x-ray beam. Small capacitors have been biased with DC voltage between 0 and ±20 V and at each step of bias a set of spotty Debye rings have been recorded. By selecting an appropriate region of interest, the evolution of a single grain peak has been followed. The fine analysis of these peaks allows to calculate the effective piezoelectric coefficient d33,eff, the proportion of each domain variants, the tetragonality inside each grain, as well as their evolution during the electrical biasing. A higher heterogeneity in samples with morphotropic phase boundary composition is observed. This study contributes to a better understanding of the local behaviors in piezo/ferroelectric polycrystalline films and in the improvement of their performance for different applications. [ABSTRACT FROM AUTHOR]

Cough is a common symptom of various respiratory diseases. However, recognizing a subject's cough using acoustic imaging can be challenging due to the complexity of coughing and the vulnerability of acoustic acquisition to external interference. This research aims to address these issues by utilizing a flexible piezoelectric ionic liquid‐doped poly(L‐lactic acid) (PLLA) sensor to gather the pressure signals from the human surface. 1‐butyl‐3‐methylimidazolium bis (trifluoromethylsulfonyl)imide ([BMIm]TFSI) ionic liquid (IL) can enhance the piezoelectric performance of PLLA thin film, the corresponding output voltage, and impact sensitivity are improved to three times and 105.1% for the PLLA/IL thin film with 1 wt% IL, 140 °C annealing 2 h and four times drawing ratio. The effect of IL on the crystallization behavior and piezoelectric properties of thin films during their preparation is investigated. The flexible PLLA/IL sensor is integrated into a wearable electronic system which collects and transmits piezoelectric signals from cough‐induced vibrations to the filter for denoising, then the acquired cough data are decomposed using the Empirical Mode Decomposition method and trained in a multi‐layer perception model to detect human coughing. It's evident that the flexible piezoelectric PLLA/IL sensors can be applied to human coughing recognition and show great potential applications in intelligent healthcare. [ABSTRACT FROM AUTHOR]

Inkjet is a versatile non‐contact printing technique that uses droplets of ink jetted from nozzles to print on a variety of substrates. Although some modern piezoelectric printheads support high viscosity fluids (>10 cP), they are currently expensive and may not be suited for many benchtop experiments in research environment. Here, the design, fabrication by 3D‐printing (no cleanroom processes or silicon micromachining are involved) and testing of a multi‐purpose single‐nozzle piezoelectric dispenser/printhead for medium‐viscosity fluids (10–60 cP) is reported. Custom control electronics are developed to drive the printhead. The design features a 200 μm diameter nozzle, suitable for nL drop generation with solutions containing nm sized particles, thus allowing the deposition of μm thick layers of functional inks in a single printing pass. The inkjet dispenser is first tested with glycerol solutions, resulting in drops of 1.9–3.6 nL with typical drop velocity of 0.5–1.3 m s−1. The developed piezoelectric dispensing system is then demonstrated in the printing of a two‐layer capacitive sensor, using silver nanoparticle ink (conductive ink) and a transparent encapsulant ink (dielectric ink). The reported piezoelectric dispenser design can be optimized for many research purposes, allowing the dispensing of functional chemicals, materials, and biomolecules. [ABSTRACT FROM AUTHOR]

Small extracellular vesicles (sEVs), a form of extracellular vesicles, are lipid bilayered structures released by all cells. Large-scale studies on sEVs from clinical samples are necessary, but a major obstacle is the lack of rapid, reproducible, efficient, and low-cost methods to enrich sEVs. Acoustic microfluidics have the advantage of being label-free and biocompatible, which have been reported to successfully enrich sEVs. In this paper, we present a highly efficient acoustic microfluidic trap that can offer low and large volume compatible ways of enriching sEVs from biological fluids by flexible structure design. It uses the idea of pre-loading larger seed particles in the acoustic trap to enable sub-micron particle capturing. The microfluidic chip is actuated using a piezoelectric plate transducer attached to a silicon-glass bonding plate with circular cavities. Each cavity works as a resonant unit, excited at the frequency of both the half wave resonance in the main plane and inverted quarter wave resonance in the depth direction, which has the ability to strongly trap seed particles at the center, thereby improving the subsequent nanoparticle capture efficiency. Mean trapping efficiencies of 35.62% and 64.27% were obtained using 60 nm and 100 nm nanobeads, respectively. By the use of this technology, we have successfully enriched sEVs from cell culture conditioned media and blood plasma at a flow rate of 10 µL min-1. The isolated sEV subpopulations are characterized by NTA and TEM, and their protein cargo is determined by WB. This acoustic trapping chip provides a rapid and robust method to enrich sEVs from biofluids with high reproducibility and sufficient quantities. Therefore, it can serve as a new tool for biological and clinical research such as cancer diagnosis and drug delivery. [ABSTRACT FROM AUTHOR]

The spectra of transmisson coefficients and absorption indices of single-domain and multidomain LaBGeO5 samples have been measured. It is shown that, to measure more exactly the optical rotation ρ, it is necessary to use the spectra of transmission coefficients not only for the cases of parallel and crossed polarizers but also at other angles between them. The obtained ρ values for both samples are described quite well by only dispersion using the Drude formula. This is in agreement with the fact that the ρ value should not change during transition to the single-domain state of the crystal at a given symmetry (P31 in the ferroelectric phase and P3121 in the paraelectric phase). It is shown that the Cherenkov-type second harmonic generation (SHG) is observed only in a polydomain sample, while the second-harmonic radiation is not polarized. The domain structure of the samples was observed by scanning electron microscopy and piezoelectric force microscopy. The presence of a labyrinth-like domain structure was shown for the multidomain sample, whereas for a single-domain sample no changes in contrast were observed within the scanned region. [ABSTRACT FROM AUTHOR]

In this review, we introduce recently developed plasma-based approaches for depositing and treating piezoelectric nanoparticles (NPs) and piezoelectric polymer films for nanogenerator (NG) and sensor applications. We also present the properties and an overview of recently synthesized or modified piezoelectric materials on piezoelectric polymers to highlight the existing challenges and future directions of plasma methods under vacuum, low pressure, and ambient air conditions. The various plasma processes involved in piezoelectric NGs and sensors, including plasma-based vapor deposition, dielectric barrier discharge, and surface modification, are introduced and summarized for controlling various surface properties (etching, roughening, crosslinking, functionalization, and crystallinity). [ABSTRACT FROM AUTHOR]

Micro-electromechanical systems (MEMS) urgently require high-performance lead-free piezoelectric thin films, which is rather difficult to achieve via the existing strategy of designing a morphotropic phase boundary. How to update the optimization methods for piezoelectric performance is a challenge. Here, we proposed a simple and interesting way, that is, constructing the self-assembly ordered domain configurations in our oriented lead-free thin films. Driven by the local strain, we realized a periodic arrangement of disordered nano-domains and ordered striped domain structures, and thus obtained an outstanding electrostrain of 1.55%. Multi-scale characterization and phase-field simulations suggest the underlying mechanism of this giant strain as the synergy between the high polarization brought about by the periodic nano-pillar-like striped domains, the highly sensitive electrical stimulation response of defective dipoles and disordered nano-domains. The presented high electrostrain supports the potential MEMS application, the proposed optimization strategy serves the next generation lead-free thin films with higher electromechanical response. [ABSTRACT FROM AUTHOR]

This document discusses the design and fabrication of micro/nano sensors and actuators, specifically focusing on micro-electromechanical systems (MEMS). MEMS devices integrate various components such as sensors, converters, and actuators into one or more chips. These devices are made from materials like silicon, metal, ceramics, and glass, which greatly influence their performance. The document also highlights the importance of process manufacturing in determining the reliability and performance of MEMS devices. The Special Issue included in the document features 11 papers that explore different aspects of MEMS/NEMS, including device design, materials, and manufacturing processes. [Extracted from the article]

Polyvinylidene fluoride (PVDF) and its copolymers present extensive application prospects, especially in the field of wearable electronics. However, utilizing nanofillers for enhanced β‐phase and piezoelectric properties faces challenges like noncontinuous interfaces, poor compatibility between nanofillers and PVDF matrix, and the requirement of high‐voltage polarization, hindering extensive domain alignment on a large scale. Herein, a method is proposed to synthesize high‐performance PVDF composites by introducing hydroxylated barium titanate (H@BTO) nanoparticles and a directional freeze‐drying method to enhance β‐phase content and piezoelectric properties without polarization. Molecular dynamics simulations reveal robust binding interactions between Ba and F atoms along with OH surface terminations on H@BTO, facilitating hydrogen bonding within the PVDF matrix, resulting in dipole alignment and increased spontaneous polarization. The composite film achieves an 86.69% β phase content and a piezoelectric coefficient of ≈14.49 pm V−1 without electric polarization. The freeze‐drying PVDF‐H@BTO composite film paired with a PA6 membrane is used to fabricate triboelectric nanogenerator, demonstrating a current density of ≈107.5 mA m−2 and an output voltage of ≈832 V. Results demonstrate that the utilization of strong binding interactions between various atoms, the hydroxyl anchoring effect, and directional freeze‐drying method as a strategy holds promising prospects for synthesizing high‐performance piezoelectric composites. [ABSTRACT FROM AUTHOR]

Thin films of Al as interconnect materials and those of AlN as wide bandgap semiconductor and piezoelectric material are of great interest for microelectronic applications. For the fabrication of these thin films via chemical vapor deposition (CVD) based routes, the available precursor library is rather limited, mostly comprising aluminium alkyls, chlorides, and few small amine-stabilized aluminium hydrides. Herein, we focused on rational precursor development for Al, their characterization and comparison to existing precursors comprising stabilized aluminium hydrides. We present and compare a series of potentially new and reported aluminium hydride precursors divided into three main groups with respect to their stabilization motive, and their systematic structural variation to evaluate the physicochemical properties. All compounds were comprehensively characterized by means of nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), electron-impact ionization mass spectrometry (EI-MS) and thermogravimetric analysis (TGA). Promising representatives were further evaluated as potential single source precursors for aluminium metal formation in proof-of-concept experiments. Structure and reaction enthalpies with NH3 or H2 as co-reactants were calculated via first principles density functional theory simulations and show the great potential as atomic layer deposition (ALD) precursors for Al and AlN thin films. [ABSTRACT FROM AUTHOR]

Most reported thin-film piezoelectric energy harvesters have been based on cantilever-type crystalline ferroelectric oxide thin films deposited on rigid substrates, which utilize vibrational input sources. Herein, we introduce flexible amorphous thin-film energy harvesters based on perovskite CaCu3Ti4O12 (CCTO) thin films on a plastic substrate for highly competitive electromechanical energy harvesting. The room-temperature sputtering of CCTO thin films enable the use of plastic substrates to secure reliable flexibility, which has not been available thus far. Surprisingly, the resultant amorphous nature of the films results in an output voltage and power density of ~38.7 V and ~2.8 × 106 μW cm−3, respectively, which break the previously reported record for typical polycrystalline ferroelectric oxide thin-film cantilevers. The origin of this excellent electromechanical energy conversion is systematically explored as being related to the localized permanent dipoles of TiO6 octahedra and lowered dielectric constant in the amorphous state, depending on the stoichiometry and defect states. This is the leading example of a high-performance flexible piezoelectric energy harvester based on perovskite oxides not requiring a complex process for transferring films onto a plastic substrate. Traditional methods to incorporate polycrystalline thin film into flexible systems are often complicated and limited by their sizes. Here, the authors introduce flexible amorphous thin film energy harvester, based on perovskite oxides, on a plastic substrate for electromechanical energy harvesting. [ABSTRACT FROM AUTHOR]

BACKGROUND: Adjustable piezoelectric effect can promote tissue regeneration and repair. Piezoelectric materials are widely used in weight-bearing tissue engineering. OBJECTIVE: To prepare a piezoelectric film material that can promote bone regeneration, and to explore its structural characterization, electrical output performance, biocompatibility, and effect of electrical output on osteogenic differentiation of rabbit bone marrow mesenchymal stem cells. METHODS: Using poly-3-hydroxybutyrateco/4-hydroxybutyrate (P34HB) as raw material, barium calcium stannate titanate powder (Ba0.94Ca0.06Sn0.08Ti0.92O3, BCST) was added according to mass ratios of 0%, 5%, 10%, 15%, and 20%. Dichloromethane was added to solve P34HB, and the thickness of 150-200 μm BCST/P34HB piezoelectric film was prepared by vacuum drying method. After polarization in the oil bath, the surface morphology, crystal phase composition, piezoelectric coefficient and open circuit voltage were tested. The effect of BCST/P34HB electrical output at 110 Hz and 0.25 N force on the proliferation and osteogenic differentiation of rabbit bone marrow mesenchymal stem cells was tested. RESULTS AND CONCLUSION: (1) Scanning electron microscopy, X-ray diffraction, water contact angle, piezoelectric coefficient and electrical output performance tests showed that when the mass ratio of BCST increased to 20%, the BCST/P34HB piezoelectric film had good piezoelectric properties (d33=5.9 pC/N) and electrical output performance (180 mV), which was closer to the suitable range of 500 mV for electrical stimulation. (2) Live and dead staining showed that on the first day of co-culture, 15% group and 20% group showed less red fluorescence. On the 5th day of culture, the number of green fluorescence in each group was significantly higher than that on the first day, and the red fluorescence was not observed in the 10%, 15% and 20% groups, and only a small amount of red fluorescence was observed in the 0% and 5% groups. (3) On the 1st, 3rd and 5th days of co-culture with rabbit bone marrow mesenchymal stem cells, Almar blue staining exhibited that the number of cells in each group showed an increasing trend with the increase of time. On the 5th day of culture, the number of cells in the 20% group was significantly more than that in the 0% group (P < 0.05). (4) On day 10 of osteogenic induction, alkaline phosphatase staining results showed that the positive rate of the 20% group was significantly higher than that of the 0% group (P=0.000 1). On day 21, alizarin red staining and quantitative analysis of calcium nodules showed a similar trend to alkaline phosphatase staining. Compared with the 0% group, the 15% group and 20% group showed significant differences (P < 0.01, P < 0.000 1). (5) The results showed that 20% BCST/P34HB films had good piezoelectric properties, electrical output properties, biocompatibility and the ability of promoting osteogenic differentiation of bone marrow mesenchymal stem cells. [ABSTRACT FROM AUTHOR]

A signal is primarily generated when two objects collide, with one falling from a specific height and the other disrupting its balance. This signal contains an important component that aids in the diagnosis of material damage. In this work, a piezoelectric thin film sensor made of polyvinylidene fluoride (PVDF) was employed to monitor the impact signal and process the recorded signal. By stacking a left and right piezoelectric film sensor, drop impact experiments were performed on rubber sheet material. The data-acquisition system captured the impact signal, and a signal processing tool was used to assess its performance. To determine the time-frequency domain visibility of the impact signal, the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) were used. The detection of the elastic signal and impact force on the material is suitable for piezoelectric film. A steel impactor strikes a silicon rubber sheet at a speed of 3.43 m/s and exerts an average impact force of 72.6 kN. To make the impact signal more visible, the noise signal can be denoised using a bandpass filter. The continuous wavelet transform has a high time-frequency resolution compared to the short-time Fourier transform. Additionally, the analysis of non-stationary signals is improved by using STFT and CWT approaches. Thus, the elastic signal detection in the material may be recognized using the average total of the signals identified by the sensor. [ABSTRACT FROM AUTHOR]

As a core functional material in acoustic resonators and filters, the elasticity of aluminum nitride (AlN) piezoelectric thin film and its correlated intrinsic properties deserve priority attention. This paper presents an in‐depth investigation of elastic softening and stiffening effect induced by stress loading in AlN piezoelectric thin film. Based on the Born‐Lande equation, the physical mechanism of such new intrinsic elastic property is revealed and predicted quantitatively for the first time from the perspective of atomic interaction forces. It is found that a maximum 6.7% modulation range of elasticity coefficient can be achieved under ultimate stress loading conditions from (−2.5, −2.5) to (2.5, 2.5) GPa. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Pressure sensors for high temperatures are extensively applied in a variety of industries processes including aerospace, energy conversion, petrochemicals, automotive and oil wells, real-time pressure detection during equipment operation is a critical concern. Silicon is widely used for piezoresistive sensing with good sensitivity, however, harsh environments with temperatures above 150 °C will lead to plastic deformation as well as current leakage. In this work, AlN/SiCN hybrid thin films systems with ultra-high piezoresistive performance are proposed and enabled by coupling with piezoelectric effect. The gauge factors of the AlN/SiCN sensing elements are from 3260 to 21428 upon different stresses, which are significantly greater than those of other piezoresistive ceramics. The piezoresistive performance of SiCN upon compressive stress is significantly enhanced by incorporation piezoelectric effect of AlN. Moreover, the interfacial strengths of the AlN/SiCN thin films are larger than those of single-layer SiCN, demonstrating that incorporation of AlN layers also improves interfacial strength of SiCN films. This work provides a crucial basis for designing novel piezoresistive sensors. [Display omitted] [ABSTRACT FROM AUTHOR]

Hypertension is a common cause of cardiovascular diseases, closely associated with the high mortality and disability rates of cardiovascular diseases such as stroke and coronary heart disease. Therefore, developing a comfortable and sustainable device for monitoring human pulse signals holds practical significance for the prevention and treatment of hypertension and cardiovascular diseases. PVDF flexible pressure sensors possess the characteristics of high sensitivity, good flexibility, and strong biocompatibility, thereby demonstrating extensive application potential in areas such as health monitoring, wearable devices, and electronic skins. This paper focuses on the development of a modified piezoelectric polymer and its application in an intelligent blood pressure monitoring system, demonstrating its outstanding performance and feasibility through a series of experiments. This research provides innovative material choices for the development of intelligent medical devices and offers beneficial guidance for the design and application of future intelligent health monitoring systems. [ABSTRACT FROM AUTHOR]

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5th and 6th generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3 films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3 layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3 and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm−1 as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3 films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1− x Ti x O3 films. [ABSTRACT FROM AUTHOR]

This work presents a thermoelectric vibration and buckling behavior of a bidirectional functionally graded piezoelectric porous (BD-FGPP) plate resting on the elastic foundation with arbitrary boundary conditions. The variation of the material properties in the FGPP plate is bidirectional, i.e. along longitudinal and thickness directions, using the modified power law distributions. Also, the BD-FGPP plate carries various porosity distributions, i.e. even, uneven and symmetric center types. The governing equation of the FGPP plate has been obtained through Hamilton's principle and solved through a higher-order finite element approach. The correctness and usefulness of the current technique are confirmed and compared with existing model outcomes available in the literature. A comprehensive parametric study has investigated the effect of the elastic foundations, porous exponent with various porosity distributions, bidirectional material exponent, temperature change, electrical loading and boundary conditions. The attained results are more valuable for designing functionally graded piezoelectric-based smart structures by considering the porosity distribution in a thermoelectric environment. [ABSTRACT FROM AUTHOR]

Sonopiezoelectric therapy (SPT) has gained ever‐increasing prominence in tumor therapy as a combination of ultrasound (US) and piezoelectric nanomaterials to generate cytotoxic reactive oxygen species (ROS) for tumor suppression. In this study, the facile hydrothermal method is used to construct the distinct 2D piezocatalyst Bi2Fe4O9 nanosheets (BFO NSs). The engineered BFO NSs can create a piezoelectric field when exposed to US irradiation, facilitating the separation of electron–hole (e−–h+) pairs to play a crucial role in Fe3+/Fe2+ circulation, which catalyzes the activation of peroxymonosulfate (PMS), resulting in an amplified production of cytotoxic sulfate radical (SO4•−). The produced SO4•− combines with ROS generated by SPT including hydroxyl radicals (•OH), and singlet oxygen (1O2), leading to the augmented oxidative tumor suppression. The BFO NSs and PMS are further integrated into a thermal hydrogel (BFO/PMS‐Gel) for in vitro and in vivo investigations on their catalytic antitumor effects. In both in vitro and in vivo studies, it is validated that BFO/PMS‐Gel, under US irradiation, significantly enhances radicals generation efficiency, which achieves superior antitumor performance while maintaining high therapeutic biocompatibility and biosafety, providing a representative paradigm of US‐activated multiple radicals production as enabled by piezoelectric nanomedicine for antitumor treatment. [ABSTRACT FROM AUTHOR]

In this study, we propose a low-cost piezoelectric flexible pressure sensor fabricated on Kapton® (Kapton™ Dupont) substrate by using aluminum nitride (AlN) thin film, designed for the monitoring of the respiration rate for a fast detection of respiratory anomalies. The device was characterized in the range of 15–30 breaths per minute (bpm), to simulate moderate difficult breathing, borderline normal breathing, and normal spontaneous breathing. These three breathing typologies were artificially reproduced by setting the expiratory to inspiratory ratios (E:I) at 1:1, 2:1, 3:1. The prototype was able to accurately recognize the breath states with a low response time (~35 ms), excellent linearity (R2 = 0.997) and low hysteresis. The piezoelectric device was also characterized by placing it in an activated carbon filter mask to evaluate the pressure generated by exhaled air through breathing acts. The results indicate suitability also for the monitoring of very weak breath, exhibiting good linearity, accuracy, and reproducibility, in very low breath pressures, ranging from 0.09 to 0.16 kPa. These preliminary results are very promising for the future development of smart wearable devices able to monitor different patients breathing patterns, also related to breathing diseases, providing a suitable real-time diagnosis in a non-invasive and fast way. [ABSTRACT FROM AUTHOR]

High-performance lead-free piezoelectric thin films are urgently required for microelectromechanical systems. In this study, thin films based on the 0.8Bi0.5Na0.5TiO3-0.2(Sr0.7Bi0.20.1)TiO3 system were prepared on Pt(111)/TiOx/SiO2/Si substrates by a sol--gel method. The large lattice distortions were induced by introducing five rare-earth ions with different ionic radii (Er/Pr/Sm/Nd/La) to achieve the purpose of regulating the piezoelectric response of the thin films with the maximum inverse piezoelectric coefficient up to 425.9 pm/V. X-ray diffraction, Raman spectroscopy, Piezoresponse force microscope, and additional testing methods were used to observe the phase composition and microstructure of the thin films to investigate the effect of doping rare-earth elements with different ionic radii at the A-site on lattice distortion, and to summarize the transformation law. This study is significant for improving the piezoelectric properties of thin films and has crucial applications in microelectronic sensing. [ABSTRACT FROM AUTHOR]

The development of 5G mobile communication imposes requirements of high frequency, miniaturization, and integration on surface acoustic wave devices. Compared with traditional piezoelectric bulk single crystal material, surface acoustic wave filters fabricated with silicon-based piezoelectric single crystal film materials exhibit advantages such as high frequency, low insertion loss, high temperature stability and so on, making silicon-based piezoelectric single crystal film material prime foundation material. Smart-Cut™ is the universal method for preparing silicon-based piezoelectric single crystal film materials, and bonding process is one of the most essential procedures. Bonding quality determines the quality of piezoelectric single crystal film and ultimately affects the performance of the devices. In this work, high-quality heterogeneous silicon-based LiTaO3 wafers with the bonding strength up to 1. 84 J/m² and bonding area over 99. 9% were achieved through optimizing low-temperature direct bonding process, which includes plasma activation, megasonic cleaning, pre-bonding, and thermal treatment. [ABSTRACT FROM AUTHOR]