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Piezoelectric thick-film (10–100 μm) sensors are mainly manufactured using lead zirconate titanate (PZT) materials, however, their performance is limited in high-temperature environments. Therefore, this paper proposes a high-temperature aluminum nitride (AlN) thick-film accelerometer. The AlN film with a thickness of 10 μm was directly deposited on the stainless steel substrate using the reactive RF magnetron sputtering technique. Compared with the silicon-based piezoelectric accelerometer, the preparation method can improve the energy transfer efficiency of the piezoelectric layer and the fracture toughness of the cantilever beam under vibration deformation and eliminate the need for complicated photolithography, etching, and thinning while being compatible with microelectromechanical systems (MEMS) technology. The experimental results indicated that the sensitivity, resonant frequency, resolution, and thermal noise (T = 300 K) of the accelerometer were 6.73 mV/g, 1193 Hz, 0.45 mg, and 39.76 nV/ Hz , respectively. Further, the designed accelerometer had long-term (6 h) and stable sensitivity at a temperature of 600 °C, indicating its broad potential for application in high-temperature environments. [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]

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]

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]

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]

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]

Thin films are widely adopted to improve resistance to chemicals, high temperature, etc. However, their hard and brittle nature imposes great challenges to achieve satisfactory surface integrity control in finishing process. To address this, an active bending methodology via piezoelectric actuator is proposed to investigate the thin film response on and beneath the surface, under different stress states. An analytical model is established and verified by experiments, which demonstrate distinct nano scratching regimes on a Si 3 N 4 film. Based on this active stress control approach, macroscale bonnet polishing was conducted and showed great improvement in surface roughness and material removal. [ABSTRACT FROM AUTHOR]

The construction of phase boundaries is a well-known strategy to enhance the performances of ferroelectrics. In the present work, BiFeO 3 and BiInO 3 with attractive high Curie temperature of 830 °C and 600 °C were considered to reveal an unexplored phase boundary. (100- x)BiFeO 3 - x BiInO 3 (x = 10, 20, 30, 40, 41, 50, 60, and 80) films, with thicknesses of approximately 289 nm, were obtained through industrial-scalable sol-gel method on Pt/Ti/SiO 2 /Si substrates. Complete solid solution can form between BiFeO 3 and BiInO 3 , changing from rhombohedral to orthorhombic structure with the increase of BiInO 3 content. The macroscopic dielectric, ferroelectric and piezoelectric properties of the thin films were systematically studied to understand the effect of the solid solution, with its phase diagram being proposed. A phase boundary near 60BiFeO 3 –40BiInO 3 is formed with much superior polarization switch and piezoelectric response, of which the Curie temperature is as high as 470 °C. The results not only deepen the understanding of BiFeO 3 -based solid solutions, but also push forward potential applications of BiFeO 3 -based films in devices particularly for potential application at elevated temperature. [ABSTRACT FROM AUTHOR]

Flexible electronics components, including wearable sensors, miniature energy supply devices, and energy harvesting systems based on polymer piezoelectric materials, have garnered extensive attention. This study focuses on the preparation of PZT nanofibers (PZT NFs) via electrospinning and their modification with polydopamine, the fabrication of PVDF/PZT NFs nanocomposite films through casting, and the production of tri-layer nanocomposite films using hot pressing. The alignment of the PZT NFs perpendicular to the electric field direction enhances the breakdown strength (E b) and facilitates the polarization of the nanocomposite films. At the interlayer interfaces within the tri-layer structure, electron traps extend the breakdown path, attenuating charge concentration and mitigating the electric field concentration effect. Consequently, the tri-layer films exhibit excellent electrical properties. Notably, the P4P tri-layer nanocomposite films have a high E b of 290.47 kV/mm and a piezoelectric coefficient of -24 pC/N. This paper presents a promising strategy for enhancing the piezoelectric properties of polymer piezoelectric materials applied in sensors and energy harvesting systems. [ABSTRACT FROM AUTHOR]

In this paper, the main motive is to mathematical explore the thin-film ferroelectric material partial differential equation which addresses the Ferroelectrics, that are being examined as key materials for applications in piezoelectric, pyroelectric electrostrictive, linear, and nonlinear optical systems. Thin ferroelectric films are used in a variety of modern electrical devices because they are both nonlinear ferroelectric and dielectric materials. This article appropriates the fractional travelling wave transformation allowing the partial differential equation to be changed into an ordinary differential equation. The considered fractional model is explored through employing the combo of G ′ G 2 − expansion method and new extended direct algebraic methodology. As an outcome, numerous types of soliton solutions like, Periodic pattern with anti-peaked crests and anti-troughs, singular solution, mixed complex solitary shock solution, mixed singular solution, mixed shock singular solution, mixed trigonometric solution, mixed periodic, periodic solution and mixed hyperbolic solution obtain via Mathematica. In addition, the G ′ G 2 − expansion technique produces singular, trigonometric, and hyperbolic solutions with different soliton families. The revealed solution will improve the mathematical analysis of this model and the associated physical phenomenon's. In order to visualize the graphical propagation of the obtained fractional soliton solutions, 3D, 2D, and contour graphics are generated by choosing appropriate parametric values. The impact of fractional parameter β is also graphically displayed on the propagation of solitons. [ABSTRACT FROM AUTHOR]

Sensing applications such as wearable electronics, electronic skin, and soft robotics using flexible piezoelectric films have received extensive attention. In this study, we fabricate large-scale 0–3 type composite films of polyvinylidene fluoride (PVDF)-doped modified lead zirconate titanate (PZT) particles (PZT@UP) through an extrusion-casting process to enhance piezoelectric properties and explain the piezoelectric performance mechanism. The introduction of PZT@UP particles improved the dielectric permittivity of the composite films and promoted the polarization of PVDF, which positively affected the piezoelectric properties of PVDF/PZT@UP films. The composite film with 25 wt% PZT@UP possessed an excellent piezoelectric coefficient (d 33) of 29 pC/N, which was 93% higher than that of neat PVDF (15 pC/N). Moreover, the addition of PZT@UP particles effectively inhibited the movement of PVDF molecular chains and improved the mechanical modulus stability of the composite films. The law of electrostrictive effect of the PVDF/PZT@UP composite films is clarified from the aspects of the movement of PVDF molecular chains, the principle of electric field distribution, and the construction of the internal electric field. Further, the similarities and differences between the piezoelectric and electrostrictive mechanisms of the PVDF/PZT@UP composite films are summarized. The extrusion-casting process combined with modified fillers shows promising potential in improving wear and tear of and electricity generation from PVDF-based composite films, leading to a profound impact on the development of large-scale fabrication of piezoelectric sensors. [ABSTRACT FROM AUTHOR]

• A multi-scale indentation model (MSI) for the stiff film-compliant substrate structures is established. • Two dimensionless numbers g /(E s −1/3 E f 1/3 t f) and τ 0 /(E s 2/3 E f 1/3 t f) are proposed to evaluate the indentation size effect. • The predicted bending stiffness by the MSI model is consistent with the experimental results. As critical components or platforms, stiff film-compliant substrate structures are widely used in micro-electro-mechanical systems (MEMS) and other devices, in which their indentation behavior plays an important role. In this work, a multi-scale indentation model (MSI) for stiff film-compliant substrate structures is established based on the strain gradient theory and the surface elastic model. With this model, the indentation size effect of the structure is investigated from three aspects: the load-depth relationship, the distribution of bending moments in the film, and the surface morphology. The results show that the indentation size effect is mainly caused by the characteristic length and the surface residual stress of the film, and it is sensitive to the modulus ratio of the film to the substrate but has little relation with Poisson's ratio and the contact radius. Based on the above analysis, two dimensionless numbers are proposed to evaluate the indentation size effect of stiff film-compliant substrate structures. Besides, the predicted bending stiffness by the theoretical model is consistent with the experimental result, which verifies the effectiveness of the MSI model. Our research sheds light on the understanding of the indentation size effect of stiff film-compliant substrate structures and provides theoretical guidance for the design of related devices. [ABSTRACT FROM AUTHOR]

In the present work, we studied structure, surface morphology, and ultrasonic response of thin film Lithium Niobium Oxide (LNO) transducers deposited on Inconel bolts, stainless steel and silicon substrates by radio frequency magnetron sputtering. The deposited transducer material was a mixture of LiNbO 3 /LiNb 3 O 8 phases, having a well-developed columnar structure. Further, the in-situ high-temperature ultrasonic response was studied in the temperature range of 18–800 °C in ambient air during short-term annealing. It was observed that long-term annealing (at 700 °C for 160 h and 800 °C for 40 h) deteriorated the ultrasonic response, owing to the irreversible change from the initial columnar structure to the porous granular structure. Dielectric and piezoelectric properties of the thin film LNO transducers were also studied. The thin film LNO ultrasonic transducers have potential applications in bolts and screws up to 700 °C. [ABSTRACT FROM AUTHOR]

The electrocaloric (EC) effect cooling technique of environmentally friendly lead-free thin film materials driven by electric fields has recently gained tremendous attention due to the urgent demand for microelectronic and integrated circuit refrigeration devices. However, the widespread use of lead-free materials in EC devices is seriously hindered due to the small electrocaloric temperature change (ΔT) within a narrow operation temperature span (T span) near room temperature. Here, lead-free Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9-x Sn x O 3 (BCZT-xSn, 0 ≤ x ≤ 0.03) thin films were prepared on substrates (Pt/Ti/SiO 2 /Si) via a sol-gel route. The BCZT-0.02Sn thin film presents an excellent EC effect (ΔT = 32.74 K, ΔS = 37.18 J kg−1 K−1) and large EC strength (ΔT/ΔE = 0.033 K cm kV−1, ΔS/ΔE = 0.037 J cm K−1 kg−1 kV−1) over a wide T span (∼26 K) under 1000 kV cm−1 near room temperature. The giant ΔT is mainly attributed to the emergence of an intermediate O phase and the formation of a multiphase (R, O and T phases) coexistence structure at room temperature, while the diffuse phase transition behavior is responsible for the wide T span. Our study provides a new idea for developing environment-friendly EC materials with an excellent room-temperature ΔT over a broad operational temperature region. [ABSTRACT FROM AUTHOR]

In this study, [001]-oriented Er-doped 0.67 Pb(Mg 1/3 Nb 2/3)O 3 -0.33PbTiO 3 (0.67PMN-0.33 PT) textured ceramics with different BaTiO 3 (BT) template concentrations were explored. The samples were prepared by tape-casting. Er3+ was added to modify the electrical properties of the polycrystalline ceramics, and the BT template was used to improve the texture of polycrystalline ceramics. The 0.67PMN-0.33 PT textured ceramics contained coexisting rhombohedral and tetragonal phases. The ceramics became increasingly textured as the sintering temperature increased up to 1250 °C. The piezoelectric coefficient of 0.67PMN-0.33 PT with 5 wt% BT was 634 pC/N, which is 1.2 times than that of randomly oriented 0.67PMN-0.33 PT. The strain of the ceramic with 5 wt% BT increased by 12.5% relative to a random control specimen. Analysis of the electrical properties and microstructure suggested that the enhancement of the piezoelectric coefficient and strain may be caused by the addition of Er3+ and the BT template. First, the directional growth of grains along the template affected the change-of-phase distribution of the system and formed a more adaptive phase. Second, Er3+ was substitutionally doped on the A-site of the perovskite to form local heterostructures. Finally, the relaxation components of the templates and Er3+ changed in the solid solution with the matrix. The solid solution of the BT templates and Er-doped-matrix powder changed the relaxation degree, which affected the interactions at the polar nanoregions and increased the piezoelectric coefficient of the ceramics. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors play a vital role in advancing the Internet of Things (IoT). However, piezoelectric sensors are limited in static pressure detection and suffer in achieving high flexibility and high sensitivity simultaneously, while piezoresistive sensors typically have slow response speeds and insensitive high-frequency detection ability. Here, we select a novel basalt fiber fabric (BFF) that can withstand high temperatures exceeding 1000 °C as a new substrate to enable one-step fabrication of piezoelectric layer based on coherently grown Pb(Zr 0.52 Ti 0.48)O 3 (PZT) thin films via a simple dipping method. The high piezoelectric coefficient g 33 of 362.5 mV·m·N−1 and the unique core-sheath structure induced stress concentration on the PZT sheath enable the flexible piezoelectric layer (bending radius < 1.45 mm) to exhibit high sensitivity (voltage sensitivity of 2.766 V/kPa within the range of 0.11–11.11 kPa) and fast response speed (11 ms). The piezoresistive layer consisting of a three-dimensional porous elastic carbon nanotube-polyurethane sponge provides a detection range comparable to piezoelectric layer (0.11–66.67 kPa). A dual-mode flexible pressure sensor (DMFS) has been developed by integrating the piezoelectric layer with the piezoresistive layer. The DMFS exhibits an extended detection range compared to previous dual-mode pressure sensors, rapid response speed, and high sensitivity, which enables simultaneous detection of both dynamic and static pressures. The DMFS can be used for keyboard and movement posture recognition, which has significant application prospects in human-machine interaction. [Display omitted] • Dual-mode flexible pressure sensor (DMFS) enables simultaneous detection of dynamic-static pressures. • Novel basalt fiber fabric was used as flexible substrate to prepare piezoelectric layer. • High sensitivity and fast response speed were achieved in piezoelectric layer. • High g 33 and the unique structure result in high piezoelectric sensitivity. • DMFS exhibits wide detection range, fast response. [ABSTRACT FROM AUTHOR]

Accurate measurement of the piezoelectric property of thin films is critical for thin film process development and device design optimization. In this paper, we proposed a wafer-level thin film characterization method that provides a non-destructive, single-side measurement solution for evaluating and in-process monitoring the transverse piezoelectric coefficient (e 31 , f). The e 31 , f of piezoelectric films was determined by measuring the deflection of circular electrode induced by the converse piezoelectric effect, with the electrodes fabricated on top of piezoelectric thin film on a silicon substrate. The constitutive equation of the unimorph plate reveals a quadratic dependence of top electrode deflection (δ) on the radius (r), which was subsequently utilized to calculate the e 31 , f while considering the electrode edge effect. Determined by non-constant variations of | δ / r 2 | from finite element method (FEM) simulation results, the electrode edge effect leads to the specification of electrode size and substrate thickness for evaluating piezoelectric coefficient. A comprehensive FEM simulation analysis of the influence of wafer size and electrode location on the accuracy of the proposed method demonstrated its reliability for wafer-level characterization. The e 31 , f measurement results of single-crystal (s-PZT) and polycrystalline PZT (p-PZT) exhibit good agreement between the proposed wafer-level method and the die-level cantilever method. These results demonstrated that the proposed single-side wafer-level method provides a reliable measurement technique for e 31 , f characterization of piezoelectric thin film. [Display omitted] • This paper proposed a wafer-level thin film characterization method that provides a non-destructive, single-side measurement solution for evaluating and in-process monitoring the transverse piezoelectric coefficient (e 31 , f). • Based on the analysis of edge effect with FEM method, the specification of electrode size and substrate thickness for evaluating e 31 , f was provided. • A comprehensive FEM simulation analysis of the influence of wafer size and electrode location on the accuracy of the proposed method demonstrated its reliability for wafer-level characterization. • The e 31 , f measurement results of s-PZT and p-PZT exhibit good agreement between the proposed method and the cantilever method. The proposed wafer-level method would be a practical technique for the actual piezoelectric MEMS engineers to evaluating and monitoring e 31 , f of piezoelectric thin films. [ABSTRACT FROM AUTHOR]

We present piezoelectric hybrid nanofibers capable of monitoring human movement, focusing on the effects of GO and rGO on the β-phase of PVDF. The β-phase in rGO is enhanced through polymer-assisted dispersion, leading to enhanced output voltage. Dispersants are used to reduce rGO aggregation, improve stability, and further boost β-phase content. Through the fabrication of piezoelectric hybrid nanofiber sensors, we successfully integrate electrospinning technology with wearable football sensors. The electrospun TX-100/rGO/PVDF piezoelectric hybrid nanofibers exhibit excellent hydrophobicity, self-powering properties, and flexibility, making them well-suited for football position sensor monitoring. [Display omitted] • Interfacial interactions enhance the β-phase crystallization of PVDF. • Triton X-100 dispersed rGO improves β-phase crystallinity and enhances electrical properties. • The synergistic effect of rGO significantly increases the output voltage. • The PENG exhibits high durability. • PENGs can be used as sensors or energy harvesters. Electrospun graphene oxide (GO)/polyvinylidene difluoride (PVDF) and reduced graphene oxide (rGO)/PVDF piezoelectric hybrid nanofibers were prepared via electrospinning to enhance the β-phase content of the PVDF crystal structure. The addition of rGO increased the number of nucleation sites in the PVDF matrix, leading to an improved β-phase content in the nanofibers. Although the inclusion of GO also increased the β-phase content, rGO addition resulted in higher output voltages due to its greater conductivity compared to GO. rGO/PVDF produced higher output voltages than GO/PVDF because rGO has few oxygen-containing groups on its carbon atoms. The 1 wt% GO/PVDF nanofibers exhibited an 86.24 % β-phase content and an average output voltage of 3.2 V under a 15 N load. The 0.5 wt% rGO/PVDF nanofibers demonstrated an 84.09 % β-phase content and an average output voltage of 3.66 V under the same load. The nonionic surfactant Triton X-100 improved rGO dispersal, enhancing its effectiveness in inducing β-phase formation, and increasing the number of stress concentration points in the nanofibers. A piezoelectric device composed of TX-100/rGO/PVDF nanofibers exhibited stable performance even after 1,500 load cycles, generating an average output voltage of 7.13 V under a 15 N load. This device serves as both an energy harvester and a footwear sensor, offering potential applications in new sports monitoring technologies and self-powered wearables. [ABSTRACT FROM AUTHOR]

In this study, a piezoelectric MEMS (Micro-Electro-Mechanical-System) speaker with thoughtfully selected resonant frequencies of dual cantilever units is designed and implemented. Based on the lead zirconium titanate (PZT) thin film with superior piezoelectric coefficient, the cantilever diaphragm is designed through the modal analysis. In the 1.5 mm by 1.5 mm cantilever array, a high-frequency actuation unit with resonance of 13.1 kHz and a low-frequency actuation unit with resonance of 6.35 kHz constitute the proposed piezoelectric MEMS speaker. The boost of sound pressure level (SPL) due to the resonant mode of low-frequency actuation unit reduces the total harmonic distortion (THD) around the subharmonic frequency of high-frequency actuation unit. Meanwhile, the asymmetric triangle diaphragm reduces the maximum stress in the structure when operating at the resonant frequency, thereby mitigating the THD spikes resulting from the nonlinear structural behavior. In pressure-field measurements, the proposed design can reach SPL ≥ 70.0 dB from 2.7 kHz to 15.0 kHz with only 0.179 V rms input. At the same time, THD remains below 3.0 % from 3.2 kHz to 20 kHz. The outstanding performance under larger input signal and bias voltage is also verified. Actuated by 0.354 V rms and 2 V DC bias, the maximum SPL achieves 111.9 dB and the SPL is higher than 80.0 dB from 3.3 kHz to 14.1 kHz. Furthermore, THD is lower than 3.0 % from 1.0 kHz to 8.9 kHz. A promising solution of piezoelectric MEMS speaker for in-ear applications is demonstrated in this study. [Display omitted] • A dual-cantilever-unit MEMS speaker with thoughtfully designed resonances. • The low-frequency unit decreases subharmonic THD of the high-frequency unit. • The asymmetric triangle design reduces the maximum stress in diaphragms. • Comprehensive investigation on the characteristics of both SPL and THD. • Good potential for integration with DD to fulfill a high-quality in-ear product. [ABSTRACT FROM AUTHOR]

In this paper, the design, fabrication and evaluation of a novel piezoelectric MEMS varifocal liquid lens are presented. The device consists of a thin film PZT actuator integrated with a liquid lens, featuring a new design with a modified disk-shaped actuator that enhances the overall displacement range. The primary innovation lies in simplifying the assembly process between the liquid/soft lens and the piezoelectric actuator, eliminating the need for vacuum bonding. Two types of liquid/soft lens materials, ionic gel and silicone oil, were investigated in different integration configurations to find the most suitable method. Analytical calculations and FEM simulations were conducted to optimize the actuator's maximum displacement, which in turn maximizes the change in the device's focal length. The developed actuator achieved around 15 µm of static displacement under a 40 V DC applied voltage, which matched well with simulation results. The shifting of the focus was clearly observed through a microscope, with the focal length estimated to change from infinity to about 31.6 mm at 35 V DC. [Display omitted] • Novel design of piezoelectric micro actuator for tunable liquid lens. • Simple integration method that does not require vacuum bonding. • The feasibility of 2 configurations and 2 liquid medium was explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly efficient piezocatalysts of BiOCl/UiO-66 heterostructure was rationally constructed. • BiOCl/UiO-66 exhibited excellent piezocatalytic activity and stability toward H 2 evolution. • Excellent piezocatalytic performance was mainly attributed to the formation of heterostructure. • A possible mechanism of BiOCl/UiO-66 heterostructure was proposed. Developing highly efficient piezocatalytic system for hydrogen production is crucial in addressing the current energy crisis. Herein, we synthesized BiOCl/UiO-66 heterostructure piezocatalyst using facile one-step solvothermal method and evaluated its performance for piezocatalytic H 2 evolution under ultrasonic vibration. Our findings reveal that BiOCl/UiO-66 heterostructure demonstrates excellent catalytic activity, yielding high piezocatalytic H 2 evolution rate of 650.9 μmol g−1 h−1, significantly surpassing that of pure BiOCl (176.5 μmol g−1 h−1) and UiO-66 (352.6 μmol g−1 h−1). Furthermore, the BiOCl/UiO-66 presents good stability throughout cyclic experiments. The improved catalytic performance of BiOCl/UiO-66 is mainly attributed to the formation of heterostructure, which can induce more active sites and the strong piezoelectric field that aids in charge carriers separation. A possible mechanism of BiOCl/UiO-66 heterostructure is proposed. This work offers practical approach to boost the hydrogen production efficiency of Bi-based piezocatalyst. [ABSTRACT FROM AUTHOR]

This article presents a relaxor ferroelectric, lead magnesium niobate-lead zirconate titanate (PMN-PZT)-thin-film-based piezoelectric drop-on-demand printhead exhibiting high jetting capability and thermal stability. Unlike conventional piezoelectric materials such as lead zirconate titanate (PZT), the PMN-PZT film demonstrates high electrical responsiveness to polarization and reduced hysteresis loss due to polar nano regions, thereby improving printhead's performance. Our research involves a comprehensive exploration of the fabrication and packaging processes for the PMN-PZT-based printhead, along with optimization of driving pulses to maximize its performance. An in-depth investigation into the dynamics of ferroelectric film's polarization identifies the best driving conditions that minimize self-heating while maximizing the dynamic displacement of the printhead. As demonstrated in the results, the unipolar pulse, capable of maintaining a consistent polarization direction of the film, yielded twice the displacement compared to driving with a bipolar pulse. Simultaneously, it reduced the thermal dissipation of the printhead by 73.4 %. Consequently, we aim to propose a method for developing ferroelectric thin film-based print heads suitable for various biological modeling research, leveraging their high productivity and thermal stability. [Display omitted] • A relaxor ferroelectric (PMN-PZT) thin film exhibits a narrow ferroelectric loop. • A narrow ferroelectric loop of film results in high piezoelectricity and less thermal loss. • In-phase unipolar pulse prevents polarization reversal in PMN-PZT film. • In-phase unipolar pulse maximizes thermal stability and displacement of the printhead. • PMN-PZT-based printhead using unipolar driving pulses is suitable for 3D bioprinting. [ABSTRACT FROM AUTHOR]

The efficiency of the piezoelectric nanogenerator is a vital factor for the superior performance of the nanogenerator to achieve a green and eco-friendly technology in the development of modern electronics. Piezoelectric nanogenerators (PNGs) have limited use in mechanical energy harvesting due to their low output performance. The output has been a major source of concern for PNG's development. A new design of PNG based on g-C 3 N 4 nanosheets(GN)/PVDF nanocomposite film (GPNC) using penetrated Cu electrode and electrostatic layer is proposed to overcome this problem. By creating numerous peripheral contacts within the piezoelectric material, the overall number of surface polarization charges increased. Also, an electrostatic contribution from graphene oxide contributes to an increased output voltage. The syngeristic effect of high % γ-nuclei, penetrated electrode, and electrostatic effect is supposed to vital for carry out significant piezoelectric outputs (V∼34.4 V and I ∼3.2 µA) and superior force sensitivity (0.93 V/kPa). In practical applications, the designed PNG can competently harvest electrical energy from various human movements, and also can detect low physiological actions. Our work offers a simple but effective perspective for high-performance piezoelectric nanogenerator fabrication and progress a stride toward self-powered day-to-day used electronics. [Display omitted] • Designed a piezoelectric nanogenerator using Cu penetrated electrode, electrostatic layer, and g-C 3 N 4 /PVDF film is proposed. • The interfacial interaction between g-C 3 N 4 and PVDF enhances the γ-phase crystallization of PVDF. • Synergistic effect of penetrated Cu NWs electrode, electrostatic GO layer greatly improves the piezoelectric outputs. • GPPNG displays an output voltage of ~34.3 V and a short circuit current of ~3.2 µA under human finger imparting. • The fabricated GPPNG can power up 22 red LEDs and several smart electronics i.e. mobile screen, watch and calculator. [ABSTRACT FROM AUTHOR]

One of the common failure mechanisms observed in electromechanical systems utilizing actuators, sensors, or flexible electronics is the occurrence of interfacial debonding. In this paper, an elastic-constant stress cohesive zone model is constructed to analyze the interface behavior of piezoelectric actuators used in electromechanical systems when imperfectly bonded to a host medium. The analytical formulation treats the piezoelectric actuator as an orthotropic thin film, employing the membrane assumption. It is assumed that the cohesive zone extends from a point, initially unknown, to the edge of the film. The governing integro-differential equation is solved for various bonding scenarios, including perfect bonding with cohesive zones at the edges, an elastic case with a delaminated zone at the center, and an elastic case with both a delaminated zone at the center and cohesive zones at the edges of the film. Detailed examinations are conducted to explore the effects of stiffness ratio parameters and critical actuating voltage on the stresses within the film and substrate as well as the cohesive zone length. The results indicate that the cohesive zone length covers 45% of the film length when the actuating voltage has a fivefold increase over the critical threshold. For the imperfect bonding, the surface in-plane stress of the substrate exhibits a tensile peak near the boundary of the cohesive zone in addition to compressive singularities at the edges of the film. The shear stress singularity factor has an asymptotic behavior as the actuating voltage goes beyond the critical threshold. The critical actuating voltage reduces by a factor of 5% only if the delamination length does not exceed 70% of the film length. • A theoretical model for an orthotropic piezoelectric film/substrate system is proposed. • The cohesive zone length covers 45% of the film length when the actuating voltage has a fivefold increase over the critical threshold. • The critical actuating voltage reduces by a factor of 5% only if the delamination length does not exceed 70% of the film length. • The shear stress singularity factor has an asymptotic behavior as the actuating voltage goes beyond the critical threshold. • SIF is linearly proportional to the actuating voltage in the elastic range. [ABSTRACT FROM AUTHOR]

With the rapid advancement of 5 G technology, the demand for surface acoustic wave (SAW) devices is experiencing exponential growth. Precisely forecasting the speed at which Rayleigh waves propagate, taking into account size effects and flexoelectric properties, is vital for enhancing SAW device design. To address this need, the study explores Rayleigh wave propagation in a stratified system consisting of a nanoscale piezoelectric guiding layer atop an isotropic elastic substrate. The governing equations, boundary conditions, and interface continuity conditions between the guiding layer and substrate are established through the Hamiltonian principle. Following this, the dispersion equations for Rayleigh waves under electric open-circuit and electric short-circuit conditions are derived and solved numerically. Additionally, the effects of flexoelectricity, inertial gradients, strain gradients, electric field gradients, and the piezoelectric guiding layer thickness on the phase velocity of Rayleigh waves are extensively explored. Our findings indicate that flexoelectricity and strain gradients elevate the phase velocity, while inertial gradients and electric field gradients result in a decrease in the phase velocity. As the frequency of Rayleigh waves increases, the impact of these factors becomes more prominent. In addition, it is observed that electric field gradients play a less significant role compared to inertial gradients and strain gradients. The findings of this study could offer valuable insights for the advancement of miniaturized SAW devices designed for high-frequency service. • Investigation of piezoelectric layer guided in-plane surface waves. • Consideration of size effects in nanoscale piezoelectric thin film. • Study of both electrically open- and short-circuit cases. • Findings show that flexoelectricity and strain gradients increase the phase velocity. • Discovery that inertial and electric field gradients decrease the phase velocity. [ABSTRACT FROM AUTHOR]

In this study, we successfully grew large-sized single crystals (12 × 11 × 8 mm³) of 0.91Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 -0.03(K 0.5 Na 0.5)NbO 3 (BNT-6BT-3KNN) with a <100> c orientation using the flux growth method. This marks the first instance of achieving such crystals. The single crystals display double hysteresis loops, featuring a maximum polarization of ∼64.6 μC/cm2. Capitalizing on the nonergodic/ergodic boundary, the single crystals exhibit a substantial strain (S m) of 0.91% at the maximum electric field of 20 kV/cm and an exceptionally high inverse piezoelectric coefficient d 33 * of 4550 pm/V. The creation of long-range domains from needle-like nanodomains and polar-nano regions under the application of an electric field was confirmed through bright-field transmission electron microscopy and piezoresponse force microscopy analyses. The phase diagram for BNT-6BT-3KNN single crystals was constructed by analyzing the temperature dependence of dielectric, ferroelectric, and electrostrain behaviors. [Display omitted] [ABSTRACT FROM AUTHOR]

Flexible pressure sensors are receiving a lot of attention due to their use in wearable electronic devices, human-machine interactive systems, and physiological signal monitoring. In this paper, we present a novel nanofiller embedded thin film based piezoelectric pressure sensor for finger tapping analysis. The active material is fabricated using poly (vinylidene fluoride) (PVDF) having zirconium oxide (ZrO 2) nanofillers. It is observed that the incorporation of ZrO 2 nanofillers has a substantial impact on the structural characteristics of PVDF polymer, leading to enhancements in its piezoelectric properties. Moreover, the PVDF/2 wt% ZrO 2 composite film sensor showed a notable maximum piezoelectric output voltage of ∼210 millivolts at a load of 20 g (0.88 kPa applied pressure). A four-fold enhancement in response is observed in case of PVDF/2 wt% ZrO 2 composite in comparison to pristine PVDF sensor. Further, a sensitivity of 0.255 ± 0.083 kPa−1 has been recorded for the composite based sensor. Additionally, maximum of 115 mV is obtained when the composite sensor is tapped manually. The recorded maximum values for impulsive pressure (38 g), high pressure (108 g), and low pressure (45 g) are 76 mV, 150 mV, and 90 mV, respectively. The sensor is efficiently able to detect robotic tapping and stress on the human fingers. An efficiency of around 90% was achieved in PVDF/ 2 wt% ZrO 2 at 5 kV/cm using PE hysteresis loop data. The findings indicate that PVDF/ZrO 2 composite based piezoelectric pressure sensor has promising capabilities for applications in wearable electronic devices and medical diagnostics. [Display omitted] • Nanofiller embedded thin film based piezoelectric pressure sensor pad for finger tapping analysis. • Active material is fabricated using poly (vinylidene fluoride) (PVDF) having zirconium oxide (ZrO 2) nanofillers. • A four-fold enhancement in response is observed in case of PVDF/2 wt% ZrO 2 composite in comparison to pristine PVDF sensor. • The sensor is efficiently able to detect the robotic finger tapping, human finger tapping and stress on fingers. [ABSTRACT FROM AUTHOR]

• PC with good compatibility with PVDF is introduced into each fiber in the form of a fiber core. • The piezoelectric properties of all-organic piezoelectric polymers can be improved while retaining high flexibility. • The PPC-2 fiber membrane has the best piezoelectric properties. In this investigation, we report the synthesis of a novel core–shell structured organic composite piezoelectric material through the application of coaxial electrospinning technology. This approach not only markedly enhances the piezoelectric properties but also preserves the inherent flexibility of the underlying piezoelectric polymer. Specifically, the incorporation of a non-piezoelectric polymer core (PC) within the PVDF nanofibers resulted in an increase in the piezoelectric coefficient (d 33) from 8 pC/N for pristine PVDF to 11 pC/N, reflecting an approximate 37.5% enhancement. Our findings represent a substantial advancement in the field of all-organic piezoelectric composite material development. [ABSTRACT FROM AUTHOR]

• We provide a theoretical method to investigate the transient behavior of a rectangular plate partially in contact with fluid subjected to a dynamic external force. • Experiments were conducted using piezoelectric film sensors to measure the force history induced by a steel ball impact to quantitatively analyze the transient response. • The transient solution demonstrates an analytical approach that connects the physical significance of the dynamic behavior of the fluid-plate coupled system in time and frequency domains. • We provides a connection between the transient behaviors and vibration characteristics. • The results indicate that changes in water depth can influence the resonance frequency shifts and wet mode shape distortions. This study aimed to investigate the transient behavior of a rectangular plate partially in contact with fluid subjected to a dynamic external force. To this purpose, a theoretical model was developed to analyze vibration characteristics and transient wave propagation. Based on superposition method, the dry mode shapes and natural frequencies of the plate under vacuum could be obtained. The dry mode shapes were treated as the fundamental function to construct the wet mode that describes the vibration behavior of the fluid-plate coupled system. The velocity potential and fluid pressure within a finite tank due to the plate deflection were derived using an equation governing the incompressible fluid. Based on the relationship between dry mode shape and wet mode shape, the fluid-plate coupled system's wet mode shape and resonant frequency could be determined from the frequency response function. Applying the normal mode method, the transient displacement of plate and fluid pressure can be obtained by solving a system of non-homogeneous differential equations. The theoretical predictions were verified by finite element method (FEM) and experimental measurements. Experiments were conducted using piezoelectric film sensors (polyvinylidene fluoride, PVDF) to measure the force history induced by a steel ball impact to quantitatively analyze the transient response. The comparison results proved that the theoretical predictions and experiments were in good agreement, including the transient responses of the displacement and in-plane strain of a plate partially submerged in the fluid. The results indicate that changes in water depth can induce resonance frequency shifts and wet mode shape distortions, which also illustrate that the vibrational properties of wet modes affect transient behavior. The proposed transient solution demonstrates an analytical approach that connects the physical significance of the dynamic behavior of the fluid-plate coupled system in time and frequency domains; it provides a connection between the transient behaviors and vibration characteristics. [ABSTRACT FROM AUTHOR]

The development of miniaturized and lightweight electronic equipment requires the improvement of the dielectric breakdown strength and energy storage performance of dielectric capacitors. Therefore, in this study, a method for obtaining an amorphous phase by reducing the annealing temperature of a material is proposed to considerably improve the electrical breakdown, and a high-polarized substance is introduced to compensate for the polarization of the material. Lead-free xBiMg 0.5 Zr 0.5 O 3 -(1-x)BaZr 0.25 Ti 0.75 O 3 (abbreviated as xBMZ-(1-x)BZT, x = 0.01, 0.02, 0.03, 0.04, and 0.05) thin films were prepared on Pt/Ti/SiO 2 /Si substrates by using the sol-gel spin-coating method. The microstructure with coexisting nanocrystalline and amorphous phases was successfully controlled by reducing the annealing temperature and employing a rapid annealing process. All the films with this microstructure exhibited extremely high breakdown strength, and the effectiveness of this method was verified. When x = 0.04, the ultra-high breakdown strength of 6640 kV/cm, high energy storage density of 81.6 J/cm3 and high energy storage efficiency of 87% were achieved. Moreover, the dielectric and energy storage performance were excellent under temperatures from 20 °C to 200 °C. This study presents a feasible approach for designing new high-performance dielectric capacitors for energy storage devices in the future. [ABSTRACT FROM AUTHOR]

Graphene-like nanomembranes made of the neighboring elements of boron, carbon and nitrogen elements, are well-known of showing outstanding physical properties. Herein, with the aid of density functional theory (DFT) calculations, various atomic configurations of the graphene-like BCN nanosheets are investigated. DFT results reveal that depending on the atomic arrangement, the BCN monolayers may display semimetallic Dirac cone or semiconducting electronic nature. BCN nanosheets are also found to exhibit high piezoelectricity and carrier mobilities with considerable in-plane anisotropy, depending on the atomic arrangement. For the predicted most stable BCN monolayer, thermal and mechanical properties are explored using machine learning interatomic potentials. The room temperature tensile strength and lattice thermal conductivity of the most stable BCN monolayer are estimated to be orientation-dependent and remarkably high, over 78 GPa and 290 W/m.K, respectively. In addition, the thermal expansion coefficient of the monolayer BCN at room temperature is estimated to be −3.2 × 10−6 K−1, which is close to that of the graphene. The piezoelectric response of the herein proposed BCN lattice is also predicted to be close to that of the h-BN monolayer. Presented results highlight outstanding physics of the BCN nanosheets. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of advanced piezoelectric thin films with large piezoelectric response on silicon substrate is a crucial technology for piezoelectric microelectromechanical systems applications. In this work, high-quality <100>-oriented 0.06Pb(Mn 1/3 Nb 2/3)O 3 -0.94Pb(Zr 0.48 Ti 0.52)O 3 (PMN-PZT) thin films were grown on the Pt/Ti/SiO 2 /Si substrate by sputtering. X-ray diffraction, scanning electron microscopy, and piezoresponse force microscopy were utilized to characterize the phase, morphologies, and domain structures. The growth parameters were optimized and thickness-dependent electrical properties were established. Well-crystalized micron-thick PMN-PZT films with high remnant polarization of 49 μC / cm 2 and giant piezoelectric coefficient (d 33) up to 484 pC / N (about twice of the polycrystalline PMN-PZT thin film and thrice of the Pb(Zr 0.52 Ti 0.48)O 3 thin film) were obtained. The excellent electrical properties make it highly advantageous for applications in MEMS devices. • High-quality <100>-oriented PMN-PZT thin films were grown on the Si substrate. • The PMN-PZT films own giant piezoelectric coefficient (d 33) of 484 pC/N. • The study investigated the effects of annealing conditions and varying thickness on the performance of the thin films. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) is a wide band gap semiconductor with interesting piezoelectric properties for many applications, including micromechanical systems (MEMS), acoustic wave sensors or energy harvesting devices. The influence of DC reactive magnetron sputtering (DCRMS) deposition parameters on the structural, crystalline, and piezoelectric properties of AlN thin films are presented. The systematic approach of Design of Experiments (DoE) has been used to evaluate the role of magnetron power, nitrogen and argon flows on the deposition process and the film properties. Magnetron power and argon flow have resulted to be the parameters causing the most significant effects on the deposition rate. AlN films have been deposited with a high crystal quality, showing low values of FWHM (0.28) and c-axis orientation parallel oriented respect to the growth direction, as evidenced by X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM). These samples also showed a high piezoelectric coefficient (d 33) of 5 pC/N for AlN thin films. This work highlights the importance of deposition parameters on the properties of the film and the important role that DoE play for its optimization with a minimum number of depositions. [Display omitted] • Systematic methodology to reduce the number of samples needed to optimize a film. • Study of how each parameter and its interactions affect the film properties. • New analysis of the AlN elemental composition through an atomic percentage profile. • Connection between crystallinity, microstructure and piezoelectricity is evidenced. [ABSTRACT FROM AUTHOR]

The acquisition of hysteresis-free and large electrostrain in lead-free piezoelectric thin films is the key issue for the development of high-performance micro actuators. The electrostrictive effect is an appropriate choice for developing hysteresis-free electrostrain. Lead-free ferroelectric compound Bi 1/2 Na 1/2 TiO 3 has great potential in realizing large electrostrain response and electrostrictive coefficient. In this work, (0.8- x)Bi 1/2 Na 1/2 TiO 3 -0.2SrTiO 3 - x BaTiO 3 (BNT-ST-100 x BT) thin films were prepared by chemical solution deposition method. The crystal structure, morphology, dielectric properties, electrostrictive effect, dielectric nonlinearity, ferroelectric properties, and electrostrain response were systematically investigated. The most significant electrostrictive effect was obtained in the ergodic relaxor BNT-ST-6BT thin film, i.e., a giant electrostrictive coefficient of 0.21 m4/C2. Meanwhile, by increasing the applied electric field, a linearly increasing strain and the maximum value of 0.82 % were obtained in this film. This work has made an important step in the electrostrictive effect study and provides a pathway to obtain hysteresis-free electrostrain in lead-free perovskite ferroelectric thin films. • A super high electrostrictive coefficient of 0.21 m4/C2 was obtained in the high-quality ergodic relaxor thin films. • The significant electrostrictive effect benefits from the large strain and low polarization intensity. • This work provides a pathway to obtain hysteresis-free electrostrain in lead-free perovskite ferroelectric thin films. [ABSTRACT FROM AUTHOR]

Integrating flexible piezoelectric nanogenerators (PENGs) into wearable and portable electronics offers promising prospects for motion monitoring. However, it remains a significant challenge to develop environmentally friendly PENGs using biodegradable and cost-effective natural polymers for mechanical energy harvesting and self-powered sensing. Herein, reduced graphene oxide (rGO) and barium titanate (BTO) were introduced into regenerated cellulose pulp to fabricate a composite porous film-based PENG. The incorporation of rGO not only increased the electrical conductivity of the porous film but also enhanced the dispersibility of BTO. Moreover, the unique pore structure of the composite porous film improved the polarization effect of the air inside the pores, thereby greatly boosting the overall piezoelectric performance. The piezoelectric coefficient of the resulting composite porous film reaches up to 41.5 pC·N−1, which is comparable to or higher than those reported in similar studies. Consequently, the PENG assembled from this cellulose/rGO/BTO composite porous film (CGB-PENG) achieved an output voltage of 47 V, a current of 4.6 μA, and a power density of 30 μW·cm−2, approximately three times the output voltage and ten times the power density of similar studies. This work presents a feasible approach for the fabrication of high-performance cellulose-based PENGs derived from recycled waste cotton textiles. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper designs and fabricates a MEMS deformable mirror with 61 electrodes driven by piezoelectric thin films (PZT) to achieve high voltage. This approach effectively corrects wavefront aberrations. Initially, the structural design and MEMS process scheme for the proposed deformable mirror are determined. Numerical simulations of electrode effects are conducted, and the working voltage and motion performance of the reflective mirror are tested using a digital interferometer. Experimental measurements of the surface deformation displacement of deformable mirrors with different electrodes are performed. A comparison of the simulation and experimental results indicates small coupling effects among the designed deformable mirror electrodes. The applied voltage and displacement response exhibit good linearity. Finally, based on the Zernike matrix model, the mirror surface shape is controlled, and Zernike polynomials of orders 2–4 are fitted. The results demonstrate that the deformable mirror has a high correction efficiency for low-order aberrations. Therefore, the proposed MEMS deformable mirror based on PZT piezoelectric thin films exhibits excellent motion and optical correction capabilities. [Display omitted] • Deformable mirrors designed to withstand sustained high pressures with less impact on overall performance. • The fitted value of voltage displacement of the designed deformed mirror is 0.997 with strong linear correlation. • The ability to correct for low-order aberrations was demonstrated by fitting Zernike's 2nd-4th order root mean square values. [ABSTRACT FROM AUTHOR]

Doping scandium in aluminum nitride (AlN) can effectively enhance the piezoelectric properties of the material, herein making ScAlN a research hotspot for the application of high-frequency and wide-bandwidth RF devices. However, there has been limited investigations into the evolution of crystal structure and composition stability under thermal annealing, especially at high temperatures. In this work, the crystal quality, surface morphology, phase and elemental distribution of sputter-deposited Sc x Al 1− x N thin films with various Sc contents were comprehensively investigated before and after high-temperature thermal annealing. It is found that the full-width-half-maximum values of the (002) diffraction peaks of Sc x Al 1−x N thin films increase with higher Sc contents, while appropriate annealing condition can enhance crystal quality. It is also revealed that Sc segregation leads to the formation of cubic-phase ScN grains, and Sc atoms diffuse towards the sapphire substrate and surface, forming a Sc 2 O 3 layer on two sides of the ScAlN core layer. These findings provide important insights into the preparation of wurtzite ScAlN films under thermal annealing and offer valuable references for the development of novel ScAlN-based devices. • Sc x Al 1−x N films with 0-20% Sc component were deposited. • Incorporating Sc into the AlN crystal lattice induces lattice strain and distortion. • The FWHM values of the XRD rocking curve of Sc 0.05 Al 0.95 N thin films is improved from 1.5° to 0.85° after annealing at 1550℃ for 30 min. • Cubic-phase ScN grains were formed inside the Al-rich ScAlN matrix after thermal annealing. • Sc atoms diffuse towards the sapphire substrate and surface, forming Sc 2 O 3 layer due to the stronger oxygen affinity of Sc compared to Al. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration and light irradiation can be used together to slow down the rapid recombination of light-induced charges during the catalytic process. One way to enhance the catalytic performance is by introducing different elements into the structure. In this study, pure bismuth ferrite (BiFeO 3) and manganese (Mn)-doped bismuth ferrite (BFMO) nanomaterials were successfully synthesized by electrostatic spinning. These materials were then tested for their ability to degrade rhodamine B (RhB). The best-performing material was BiFe 0.85 Mn 0.15 O 3 , which achieved almost complete removal of RhB within 100 min. The degradation rate of this material was 3.3 times higher than that of pristine BiFeO 3. This enhanced catalytic activity can be attributed to the wider range of light absorption and the synergistic enhancement of the piezoelectric response, which promotes the movement of free carriers. In addition, the synthesized catalysts have good stability and reusability, with little metal leaching after multiple uses. Free radical scavenging experiments tests showed that ·OH and holes are the main active species in the catalytic process. This work paves a new approach for creating highly efficient piezoelectric catalysts and expands the application of BiFeO 3 -based materials for wastewater purification. • BiFeO 3 and Mn-doped BiFeO 3 nanomaterials were successfully synthesized by electrostatic spinning. • The piezoelectric photocatalytic performance of BiFeO 3 was significantly enhanced after appropriate Mn doping. • This work achieves efficient piezoelectric degradation of organic pollutants in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Piezoelectric actuation facilitates MEMS-to-NEMS transition, showing promising scaling of the device surface area. • Deposition of AlN piezoelectric thin films on vertical sidewalls allows to utilize the M/NEMS designs with the in-plane motion. • FEM simulation demonstrates the AlN in-plane transducer as jump-to-contact latching relay with Casimir Forces coupling and controllable stiction. • In-plane transducer on vertical sidewalls is fabricated with the promising quality of AlN c-axis orientation through atomic layer deposition. One of the key advantages of Piezoelectric MEMS (PiezoMEMS) is its scalability, overcoming issues commonly associated with alternative transduction methods. However, the breadth and depth of studies on scaling the fabrication process from PiezoMEMS to NEMS (Nano-Electro-Mechanical Systems) remain limited. Effective MEMS miniaturization not only improves energy efficiency and surface area reduction but also enables the coupling of nanoscale physics, particularly Casimir Forces, with the NEMS design, device operation, and fabrication opportunities. Here, combined with the finite element method (FEM) modeling, the experimental aluminum nitride (AlN) nanotransducer fabrication is performed to address the fabrication challenges with beam-based in-plane nanostructures and to develop the piezoelectric NEMS design utilizing a controllable stiction behavior. The FEM modeling demonstrates that the designed structure featuring a 220 nm thick silicon (Si) beam with AlN layers located on vertical sidewalls exhibits controllable jump-to-contact and jump-off-contact behaviors. Based on modeling results, a complete piezoelectric sidewall transducer structure is fabricated. The final transducer represents a patterned Si nanobeam with the Molybdenum-AlN-Aluminum transducer located on the vertical sidewalls. The presented findings not only open new opportunities in the piezoelectric MEMS scaling but also establish a platform for the design of innovative "more-than-a-Moore" devices, such as in-plane mechanical latching switches. [ABSTRACT FROM AUTHOR]

For the practical implementation of Cr(Ⅵ) removal, effective and recyclable water treatment technology is essential. Polarized electric fields inside piezoelectric materials have proved to be a promising technique for facilitating photogenerated charge separation. In this work, Z-scheme heterojunction photocatalyst HKUST-1/BiVO 4 and organic piezoelectric material PVDF were combined through electrospinning to create a novel flexible fiber PVDF-HKUST-1/BiVO 4 (PVDF-HV) piezo-photocatalyst membrane. When the amount of HKUST-1/BiVO 4 powder was 2.4% and the diameter of the obtained fiber film was 10 cm, the optimal reduction efficiency can be achieved by the piezoelectric photocatalytic reduction in solution with initial pH=2, and the piezo-photocatalytic efficiency of PVDF-HV reached up to 85.33% within 120 min, which was about 1.35 times and 2.19 times greater than that of single photocatalysis and piezoelectric catalysis, respectively. It successfully promoted photo charge separation based on the piezoelectric field in PVDF and the heterojunction produced between HKUST-1 and BiVO 4. This research developed an efficient strategy for multi-path collection and exploitation of natural solar energy and vibration energy to boost photoactivity. [Display omitted] • Z-scheme HKUST-1/BiVO 4 and piezoelectric PVDF were combined through electrospinning. • Superior piezo-photocatalytic activity has been obtained by PVDF-HKUST-1/BiVO 4. • Synergistic effects of heterojunction and piezoelectricity was addressed. • The catalytic mechanism under ultrasound and visible light was revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The metal-free PTFE/g-C 3 N 5 catalysts were successfully prepared. • The piezo-catalytic performance of g-C 3 N 5 was enhanced by introducing PTFE. • The optimized catalysts showed twice the degradation efficiency compared to g-C 3 N 5. • Roles of •OH and •O 2 – radicals in the degradation of TC were studied. • Possible degradation pathways and toxicity evaluation were explored. Piezoelectric catalysis has garnered significant attention in the realms of environmental protection, energy conservation, and the green economy. Interestingly, substantial research has concentrated on designing and enhancing the piezoelectric performance of metallic piezo-catalysts like piezoceramics, while metal-free piezo-catalysts have not received extensive scrutiny. In this study, a series of metal-free-based piezo-catalysts were prepared by modifying porous carbon nitride material (g-C 3 N 5) with polytetrafluoroethylene (PTFE). The resulting PTFE/g-C 3 N 5 high piezoelectric properties (d 33 is 21 × 10-12C/N), surpassing the original g-C 3 N 5 by 2.1 times. Under low frequency ultrasound activation, the optimized PTFE/g-C 3 N 5 demonstrated the ability to remove 94.17 % of tetracycline (TC), 92.0 % of oxytetracycline, 88.6 % of chlorotetracycline, 69.4 % of carbamazepine and 69.447 % of levofloxacin. A detailed kinetic study of TC experimental removal and an exploration of the influence of experimental conditions on the rate constant were conducted. This work is anticipated to offer a viable method for developing of novel piezo catalysts for energy conservation and environmental applications. [ABSTRACT FROM AUTHOR]

In this paper, we will provide information on the growth mechanism of 3C-SiC using alternating supply deposition (ASD). SiH 4 and C 3 H 8 were introduced successively in a low-pressure chemical vapor deposition (LPCVD) system at 1000 °C, forming a stoichiometric polycrystalline 3C-SiC thin film on Si substrates. We demonstrate the influence of different gas flow rates on thin film properties. In detail, altering the flow rates of the precursors and the carrier gas resulted in changes of the growth rate, the surface roughness, the crystal growth mechanisms as well as the crystal quality. Hydrogen inhibition and passivation are proposed to be the main effects influencing the growth behavior of ASD thin films. Applying ASD to grow 3C-SiC thin films with precursors from low to high flow rates resulted in a transition of different growth mechanisms influencing the surface roughness and grain size. Furthermore, we could prove that ASD is a cyclic step-by-step carbon-assisted redistribution of a prior deposited silicon film. This is shown by contact angle measurements of three differently terminated surfaces during the specific phases of one ASD cycle. High resolution transmission electron microscopy (HRTEM) analysis showed a continuous and homogenous thin film and confirmed the absence of silicon- or carbon-rich layers. ASD enables 3C-SiC thin films with customized properties for tailored micro electromechanical system (MEMS) applications. [Display omitted] • Tailored 3C-SiC thin film properties for MEMS applications using alternating supply deposition (ASD). • Discussion of control parameters affecting 3C-SiC properties during deposition. • Changes of the gas flow shows high impact on the roughness and crystallinity. • Characterization of the carbonization layer at the 3C-SiC/Si interface. • Insights into alternating supply deposition (ASD) growth mechanism. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAp) qualities such as biocompatibility and piezoelectricity make it an excellent material for biomedical applications. Here, HAp thin film samples were fabricated onto silica substrates to study their piezoelectric behavior with optical interference. Thin solid films were deposited using previously synthesized HAp powder, sol-gel, and spin-coating techniques. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, Raman, and UV-Vis spectroscopies. The statical piezoelectric effect of the samples was studied by using a finite element method and computational software. Additionally, an experimental Bode analysis allows computing the internal electrical components of the films using high-frequency AC voltage. The electrical behavior is related to the equivalent circuit of a piezoelectric crystal, which indicates the range of frequencies where the electromechanical effect is maximum. A Sagnac interferometer was used to characterize the strain in the HAp as a function of the electrical input frequency. The displacement of the interferometric fringe pattern allows us to estimate the change in the thickness of the sample and compute the piezoelectric constant. The synthesis of HAp thin films with piezoelectric properties provides an effective way to produce sensors and actuators for technological applications. [Display omitted] • Hydroxyapatite thin films samples were studied in their piezoelectric properties. • A Sagnac interferometer was used to compute nanodeformations in the samples. • The synthesis of the films is an effective way to produce sensors and actuators. • The sample performance is comparable to other conventional biosensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag@SBTO and SBTO have different piezo catalytic performances for pollutant removal. • The inactivation efficiency of E. coli K12 with Ag@SBTO5 is 21.3 times much higher than that of SBTO. • Different active species demonstrated diverse activities for different pollutants. • Electron transfer behavior during ball milling was explained in depth. • Ball milling lowered the Schottky barrier and regulated the type of reactive oxygen species and redox activity. Loading noble metal nanoparticles on piezoelectric substrates to form the Schottky barrier is believed to be an effective way to promote charge separation and enhance the piezocatalytic performance. The presence of the exceeded Schottky barrier would influence the generation of reactive oxygen species (ROS). However, the detailed correlation between the Schottky barrier height and the type of ROS is not well established. Herein, a type of Aurivillius material, SrBi 2 Ta 2 O 9 (SBTO) and its composite materials Ag loaded SBTO (Ag@SBTO), were synthesized for different bacteria inactivation and pollutants degradation under ball milling (BM). The results showed that Ag@SBTO3 (0.76 wt% Ag) could lead 7.46 log 10 of E. coli K12 inactivation, which was 21.3 times higher than that of SBTO. And Ag@SBTO3 also can achieve about 98.05% of Oxytetracycline degradation, while SBTO showed a better efficiency in Minocycline Hydrochloride and Rhodamine B degradation, the degradation efficiency can reach up to 92.60% and 75.04%, respectively. The variety of catalytic efficiency can be attributed to the different Schottky barrier height and the reduced activation energy of the piezo system when they were subjected to BM effect, which ultimately changed the type of ROS. Our results confirmed that ·OH and ·O 2 – were the main ROS for SBTO and Ag@SBTO3 during the experiments, respectively, and BM lowering the Schottky barrier of Ag loading piezoelectric material was a facile strategy to generate different ROS for a wide range of applications in water pollution control and drinking water safety. [ABSTRACT FROM AUTHOR]

In recent years, self-sensing composite materials based on the direct piezoelectric effect have attracted widespread interest as they combine the composite material's mechanical performances with the piezoelectric phase's sensing capability. In this context, piezoelectric nanofibers exhibit minimal impact on the mechanical structure of the composite – differently from bulky films or ceramic disks - and represent a promising strategy for robotic applications or wearable devices. This work aims to develop a self-sensing laminate based on piezoelectric core-shell nanofibers (PEDOT:PSS-based core and P(VDF-TrFE)-based shell). Each layer of the laminate is made of a flexible epoxy material and embeds aligned nanofibers. By orthogonally overlapping two layers, the intersection points of the matrix-like arrangement of the nanofibers generate a network of piezoelectric pixels, which are responsible for sensing. Such a self-sensing composite material exhibited a noticeable capability to recognize the exact position of a mechanical stimulus on its surface. [Display omitted] • Core-shell piezoelectric nanofibers were fabricated via coaxial electrospinning. • The nanofibers were embedded in a matrix-like disposition in a hosting material. • The intersection of orthogonal nanofibers generates a network of sensitive pixel. • The composite material is able to recognize the position of an impact on its surface. [ABSTRACT FROM AUTHOR]

• New sensitivity-improving approach for mode-localized MEMS mass sensors is presented. • This improvement is based on incorporating piezoelectric thin films pattern. • Nonlinear Ritz-based ROM of the design is obtained through the Hamilton principle. • System's nonlinear dynamics is investigated employing the harmonic balance method. • This approach improves the mode-localized sensors sensitivity more than two times. This investigation focuses on developing a new sensitivity-improving approach for high-order mode-localized mass micro-sensors by utilizing the capabilities of piezoelectric materials. To this end, an electrostatically coupled micro-beam as the building block of MEMS mass sensors is considered. The present design includes the incorporation of a patterned arrangement of piezoelectric thin films placed on the lower electrode of the system. The nonlinear reduced equations of motion for the introduced tunable system are derived by employing the Hamilton principle in conjunction with the Euler-Bernoulli beam theory and the Ritz discretization procedure. These equations are subsequently solved using the harmonic balance method. The present findings are validated by those available in the literature for the case of static excitation. In addition, the eigenvalue loci of the proposed system have been compared and verified by those obtained through three-dimensional finite element simulations carried out in COMSOL Multiphysics commercial software. Taking the shift of the amplitude ratio as the measure demonstrating the sensitivity of the proposed design, it is observed that incorporating piezoelectric excitation can significantly enhance the efficiency of these systems more than two times in comparison to conventional mode-localized mass micro-sensors without piezoelectric layers. [ABSTRACT FROM AUTHOR]

Piezoelectric biomaterials are intrinsically suitable to convert mechanical energy to electrical output and achieve electricity generation, in vivo / in vitro real-time monitoring, and sensing in biological systems. However, the inability to fabricate piezoelectric bio-materials with excellent piezoelectricity, full biodegradability, and good biocompatibility remains a challenge toward practical applications. As a solution, we present a bio-piezoelectric thin film with macroscopic piezoelectric output, high stability, fast response ability, flexibility, biocompatibility, and biodegradability based on nascent silk nanoribbons (SNRs) with high silk II-type structure. The solvent systems influence the meso/nanostructure and the piezoelectric performance of silk materials. Compared with other silk materials, the SNR fabricated by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation system (T-SNR) maintains higher silk II-type structure and more stable crystalline structure. The T-SNR film possesses electrostriction effect without electrical poling treatment. It presents an apparent piezoelectric constant (d 33) of 7.7 pm/V and a piezoelectric voltage coefficient (g 33) of 0.58 Vm/N, such values are superior to most reported bio-films. The piezoelectric T-SNR film can realize in vivo/in vitro real-time monitoring, sensing, and self-power ability. With its natural compatibility and degradability, the T-SNR film exhibits the potential for various implantable and wearable applications and may enable the development of fully biodegradable transient electromechanical devices. [Display omitted] • Nascent silk nanoribbons with high silk II-type structure were directly exfoliated from natural silk. • The silk nanoribbon film shows an apparent d 33 of 7.7 pm/V and g 33 of 0.58 Vm/N. • The piezoelectric silk nanoribbon film can realize in vivo / in vitro real-time monitoring, sensing, and self-power ability. [ABSTRACT FROM AUTHOR]