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With the development trend of miniaturization, lightweight and portability of electronic equipment, piezoelectric devices have been widely applied to transducers, sensors and energy harvesters. Piezoelectric polymers, like poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), possess the advantages of light weight, good flexibility, and simple preparation methods. However, P(VDF-TrFE) films is not entirely composed of piezoelectric phase (β phase), so increasing the content of β-phase is very important for the piezoelectric property of P(VDF-TrFE) films. Doping nanomaterials with unique properties has been proved to be a feasible way to increase the content of β-phase. In this paper, hexagonal boron nitride (h-BN) nanosheets, a kind of 2-dimensional van der Waals materials with wide bandgap, as filler were doping into poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric films by solution casting method. The composite films as designed, in which h-BN nanosheets were uniformly dispersed in P(VDF-TrFE), achieved higher contents of piezoelectric phase (β phase). Compared with pure P(VDF-TrFE) films, the optimal P(VDF-TrFE)/BN piezoelectric film achieved a much higher piezoelectric coefficient (d 33) (∼42 pC/N), also leading to a higher piezoelectric voltage output than that of pure P(VDF-TrFE). By laminating the P(VDF-TrFE)/BN films as designed with FeSiB Metglas, high magnetoelectric voltage coefficients under zero and low DC magnetic bias were achieved. In summary, this paper presents a feasible and potential method for improving PVDF piezoelectricity, which has been successfully applied in high performance magnetoelectric devices. [ABSTRACT FROM AUTHOR]

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

Solid‐state Li metal battery has attracted increasing interests for its potentially high energy density and excellent safety assurance, which is a promising candidate for next generation battery system. However, the low ionic conductivity and Li+ transport number of solid‐state polymer electrolytes limit their practical application. Herein, a composite polymer electrolyte with self‐inserted structure is proposed using the layered double hydroxides (LDHs) as dopant to achieve a fast Li+ transport channel in poly(vinylidene‐co‐trifluoroethylene) [P(VDF‐TrFE)] based polymer electrolyte. In such a composite electrolyte, P(VDF‐TrFE) polymer has an all‐trans conformation, in which all fluorine atoms locate on one side of the polymer chain, providing fast Li+ transport highways. Meanwhile, the LDH can immobilize the anions of Li salts based on the electrostatic interactions, promoting the dissociation of Li salts, thereby enhancing the ionic conductivity (6.4 × 10−4 S cm−1) and Li+ transference number (0.76). The anion immobilization effect can realize uniform electric field distribution at the anode surface and suppress the dendritic Li growth. Moreover, the hydrogen bonding interaction between LDH and polymer chains also endows the composite electrolyte with strong mechanical properties. Thus, at room temperature, the Li || Li symmetric cells can be stably cycled over 1000 h at a current density of 0.2 mA cm−2, and the full cells with LiFePO4 cathode deliver a high capacity retention (>95%) after 200 cycles. This work offers a promising route to construct solid‐state polymer electrolytes with fast Li+ transport. [ABSTRACT FROM AUTHOR]

This paper introduces a flexible array Plantar sensor fabricated through the high-voltage electrospinning process of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ，incorporating stannic oxide nanoparticles （SnO2NPS）and graphene (GR) composite nanofilm. The surface morphology, β-phase crystal content, piezoelectric performance, composition, and structure of the composite piezoelectric films were evaluated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and a vibration platform. Experimental findings reveal that P(VDF-TrFE)/SnO2NPS/GR composite films containing 5% SnO2NPS and 0.1% GR exhibit superior open-circuit voltage and short-circuit current, measuring 22.43 V and 12.95 uA, respectively. These values are approximately 1.59 times and 1.34 times higher than those of the 5% P(VDF-TrFE) composite film and about 2.37 and 2.16 times higher than those of pure P(VDF-TrFE). A flexible piezoelectric sensor was fabricated using this composite film, and the mechanical properties and electrical impedance behavior of the sensor were investigated and analyzed.A multi-channel foot pressure collection and classification system was established based on this sensor, and a Parkinson's disease machine learning model for multi-channel foot pressure collection was investigated. Various machine learning models for Parkinson's disease were compared, and a fine K Nearest Neighbors（KNN） Parkinson's disease classification model with an accuracy of 97.1% was proposed. This offers a novel solution for Parkinson's disease diagnosis and holds significant reference value. [ABSTRACT FROM AUTHOR]

Films of piezoelectric poly(vinylidene fluoride) (PVDF) and its copolymer P(VDF-TrFE) have been studied intensively for their potential application in piezoelectric sensing devices. The present work focuses on tuning the piezoelectric properties of P(VDF-TrFE) films via incorporating Ag and polydopamine co-decorated PZT (Ag@PDA@PZT) particles. Ag@PDA@PZT particles can effectively improve the β-phase content and piezoelectric properties of P(VDF-TrFE) films. The highest open-circuit voltage and short-circuit current of P(VDF-TrFE)-based flexible pressure sensors incorporating Ag@PDA@PZT particles are ~30 V and ~2.4 μA, respectively. The flexible sensors exhibit a response to different body movements, providing a practical and potentially useful basis for human−machine interface applications. [ABSTRACT FROM AUTHOR]

Abstract Solid‐state Li metal battery has attracted increasing interests for its potentially high energy density and excellent safety assurance, which is a promising candidate for next generation battery system. However, the low ionic conductivity and Li+ transport number of solid‐state polymer electrolytes limit their practical application. Herein, a composite polymer electrolyte with self‐inserted structure is proposed using the layered double hydroxides (LDHs) as dopant to achieve a fast Li+ transport channel in poly(vinylidene‐co‐trifluoroethylene) [P(VDF‐TrFE)] based polymer electrolyte. In such a composite electrolyte, P(VDF‐TrFE) polymer has an all‐trans conformation, in which all fluorine atoms locate on one side of the polymer chain, providing fast Li+ transport highways. Meanwhile, the LDH can immobilize the anions of Li salts based on the electrostatic interactions, promoting the dissociation of Li salts, thereby enhancing the ionic conductivity (6.4 × 10−4 S cm−1) and Li+ transference number (0.76). The anion immobilization effect can realize uniform electric field distribution at the anode surface and suppress the dendritic Li growth. Moreover, the hydrogen bonding interaction between LDH and polymer chains also endows the composite electrolyte with strong mechanical properties. Thus, at room temperature, the Li || Li symmetric cells can be stably cycled over 1000 h at a current density of 0.2 mA cm−2, and the full cells with LiFePO4 cathode deliver a high capacity retention (>95%) after 200 cycles. This work offers a promising route to construct solid‐state polymer electrolytes with fast Li+ transport.

Abstract Introduction Breast cancer ranks second as the most common malignancy globally, after lung cancer. Among the various subtypes of breast cancer, HER2 positive breast cancer (HER2 BC)poses a particularly challenging prognosis due to its heightened invasiveness and metastatic potential. The objective of this study was to construct a composite piezoelectric nanoparticle based on poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) for imaging and treatment of HER2 BC. Method By reshaping the crystal structure of P(VDF-TrFE) piezoelectric nanoparticles, improving hydrophilicity, and incorporating imaging capabilities, we developed piezoelectric composite nanoparticles (PGd@tNBs) that integrate imaging and therapeutic functions. The in vitro characterization encompassed the assessment of piezoelectric properties, hydrophilicity, imaging performance, and therapeutic efficacy of these particles. The targeting and therapeutic effectiveness of PGd@tNBs particles were further validated in the SK-BR3 cell line and subsequently confirmed in HER2-positive tumor-bearing mice. Results The nanoparticle demonstrated excellent biocompatibility and impressive multimodal imaging performance. Magnetic resonance imaging (MRI) observations revealed significant accumulation of PGd@tNBs particles in the HER2 positive tumor, exhibiting superior contrast-enhanced ultrasound performance compared to traditional ultrasound contrast agents, and small animal in vivo imaging showed that PGd@tNBs particles were primarily excreted through respiration and urinary metabolism. Piezoforce Microscopy characterization highlighted the outstanding piezoelectric properties of PGd@tNBs particles. Upon targeted binding to HER2-BC, ultrasound stimulation influenced the cell membrane potential, leading to reversible electroporation. This, in turn, affected the balance of calcium ions inside and outside the cells and the mitochondrial membrane potential. Following ingestion by cells, PGd@tNBs, when exposed to ultrasound, triggered the generation of reactive oxygen species (ROS), resulting in the consumption of glutathione and superoxide dismutase and achieving sonodynamic therapy. Notably, repeated ultrasound stimulation, post PGd@tNBs particles binding and entry into cells, increased ROS production and elevated the apoptosis rate by approximately 45%. Conclusion In conclusion, the PGd@tNBs particles developed exhibit outstanding imaging and therapeutic efficacy, holding potential for precise diagnosis and personalized treatment of HER2 BC.

Introduction: Breast cancer ranks second as the most common malignancy globally, after lung cancer. Among the various subtypes of breast cancer, HER2 positive breast cancer (HER2 BC)poses a particularly challenging prognosis due to its heightened invasiveness and metastatic potential. The objective of this study was to construct a composite piezoelectric nanoparticle based on poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) for imaging and treatment of HER2 BC. Method: By reshaping the crystal structure of P(VDF-TrFE) piezoelectric nanoparticles, improving hydrophilicity, and incorporating imaging capabilities, we developed piezoelectric composite nanoparticles (PGd@tNBs) that integrate imaging and therapeutic functions. The in vitro characterization encompassed the assessment of piezoelectric properties, hydrophilicity, imaging performance, and therapeutic efficacy of these particles. The targeting and therapeutic effectiveness of PGd@tNBs particles were further validated in the SK-BR3 cell line and subsequently confirmed in HER2-positive tumor-bearing mice. Results: The nanoparticle demonstrated excellent biocompatibility and impressive multimodal imaging performance. Magnetic resonance imaging (MRI) observations revealed significant accumulation of PGd@tNBs particles in the HER2 positive tumor, exhibiting superior contrast-enhanced ultrasound performance compared to traditional ultrasound contrast agents, and small animal in vivo imaging showed that PGd@tNBs particles were primarily excreted through respiration and urinary metabolism. Piezoforce Microscopy characterization highlighted the outstanding piezoelectric properties of PGd@tNBs particles. Upon targeted binding to HER2-BC, ultrasound stimulation influenced the cell membrane potential, leading to reversible electroporation. This, in turn, affected the balance of calcium ions inside and outside the cells and the mitochondrial membrane potential. Following ingestion by cells, PGd@tNBs, when exposed to ultrasound, triggered the generation of reactive oxygen species (ROS), resulting in the consumption of glutathione and superoxide dismutase and achieving sonodynamic therapy. Notably, repeated ultrasound stimulation, post PGd@tNBs particles binding and entry into cells, increased ROS production and elevated the apoptosis rate by approximately 45%. Conclusion: In conclusion, the PGd@tNBs particles developed exhibit outstanding imaging and therapeutic efficacy, holding potential for precise diagnosis and personalized treatment of HER2 BC. [ABSTRACT FROM AUTHOR]

We propose a characterization method based on modulated thermoreflectance technique for measuring directly the electrocaloric (EC) effect. First, the EC response in BaTiO3-based multilayer capacitors (MLC) with Y5V specification was measured using thermoreflectance set-up. Further, the direct measurement method was implemented on P(VDF-TrFE) 55/45 thin films deposited on flexible PET substrate, where the frequency dependence of the EC response in these films was investigated. It was noted that the P(VDF-TrFE) EC temperature responses depend on the operation voltage frequency, thus we considered three frequency ranges using square voltage waveform. Three distinct types of EC temperature variation responses were observed depending on the waveform frequency range. In addition, the EC temperature variation of the thin film with a thickness of 1.4 µm was measured via thermoreflectance. The data reveal a large EC effect occurring at room temperature where a temperature change ΔT = 1.14°C was induced under a field of 82 MV/m. [ABSTRACT FROM AUTHOR]

[Display omitted] Electroactive materials are increasingly being used in strategies to regenerate cardiac tissue. These materials, particularly those with electrical conductivity, are used to actively recreate the electromechanical nature of the cardiac tissue. In the present work, we describe a novel combination of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), a highly electroactive polymer, with graphene (G), exhibiting high electrical conductivity. G/P(VDF-TrFE) films have been characterized in terms of topographical, physico-chemical, mechanical, electrical, and thermal properties, and studied the response of cardiomyocytes adhering to them. The results indicate that the crystallinity and the wettability of the composites remain almost unaffected after G incorporation. In turn, surface roughness, Young modulus, and electric properties are higher in G/P(VDF-TrFE). Finally, the composites are highly biocompatible and able to support cardiomyocyte adhesion and proliferation, particularly surface treated ones, demonstrating the suitability of these materials for cardiac tissue engineering applications. [ABSTRACT FROM AUTHOR]

This study presents an advanced two‐step hot‐pressing process for fabricating the 1‐3 type Pb(ZrTi)O3/poly(vinylidene fluoride‐trifluoroethylene) (PZT/P(VDF‐TrFE)) piezoelectric composite sheets, demonstrating significant potential for nondestructive evaluation and information storage applications. The engineered columnar architecture within these composites induces a two‐phase clamping effect, which, upon polarization, facilitates the elongation of PZT and suppresses its lateral vibrations, thus enhancing the electromechanical coupling effect as verified by COMSOL simulations. A notable dielectric constant of 2200 at 100 Hz and a coupling coefficient of 0.725 was achieved with specific geometric modifications to the PZT/P(VDF‐TrFE) sheets. These findings suggest that P(VDF‐TrFE) as a polymer matrix exceeds the performance of conventional epoxy matrices, offering a novel approach to designing 1‐3 type piezoelectric composites. Highlights: P(VDF‐TrFE) effectively drives the elongation strain of internal PZT columns.COMSOL simulation clarifies the clamping effect of piezoelectric P(VDF‐TrFE).PZT/P(VDF‐TrFE) shows a higher kt of 0.725 than that of pure PZT samples. [ABSTRACT FROM AUTHOR]

Developing energy harvesting devices is crucial to mitigate the dependence on conventional and rigid batteries in wearable electronics, ensuring their autonomous operation. Nanogenerators offer a cost‐effective solution for enabling continuous operation of wearable electronics. Herein, this study proposes a novel strategy that combines freeze‐casting, freeze‐drying, and printing technologies to fabricate a fully printed triboelectric nanogenerator (TENG) based on polyvinylidene fluorid‐etrifluoroethylene P(VDF‐TrFE) porous aerogel. First, the effects of porosity and poling on the stretchability and energy harvesting capabilities of P(VDF‐TrFE) are investigated, conducting a comprehensive analysis of this porous structure's impact on the mechanical, ferroelectric, and triboelectric properties compared to solid P(VDF‐TrFE) films. The results demonstrate that structural modification of P(VDF‐TrFE) significantly enhances stretchability increasing it from 7.7% (solid) to 66.4% (porous). This modification enhances output voltage by 66% and generated charges by 48% for non‐poled P(VDF‐TrFE) porous aerogel films compared to their non‐poled solid counterparts. Then, a fully printed TENG is demonstrated using stretchable materials, exhibiting a peak power of 62.8 mW m−2 and an average power of 9.9 mW m−2 over 100 tapping cycles at 0.75 Hz. It can illuminate light‐emitting diodes (LEDs) through the harvesting of mechanical energy from human motion. This study provides a significant advance in the development of energy harvesting devices. [ABSTRACT FROM AUTHOR]

Poly (vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)] has three crystal forms, including paraelectric α, ferroelectric β, and γ phases. In previous studies, the properties and performances of P(VDF‐TrFE) have been the focus of research. However, the formation mechanism and regulation mode of various crystal forms remain unclear. Therefore, it is an important topic for further research to elucidate, summarize, and prospect the polymorphism of P(VDF‐TrFE) and regulate the crystal forms. This review systematically summarizes the crystalline structure and phase transition between ferroelectric and paraelectric phase of P(VDF‐TrFE) crystals; discusses the influence of annealing, blending and electric field on the crystallinity, selection of polymorphic crystals, and phase transition behavior between them; reviews the effects of annealing, melt‐recrystallization, substrate and nanoconfinement on the crystal orientation. Finally, the effects of the crystal structure of P(VDF‐TrFE) on its properties are briefly summarized. [ABSTRACT FROM AUTHOR]

Organic polymers are of interest due to their numerous promising potential applications in the area of energy harvesting and sensing. In this context, piezoelectric and ferroelectric polymers are subject to intense research; however, it is challenging to understand polarization switching in such systems. The focus of the present study is to thoroughly evaluate the finer details of polarization reversal in poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) thin films. The intrinsic features arising from the true values of (switching) polarization and extrinsic features associated with the presence of non‐switching contributions, i.e. leakage current and linear dielectric component, have been investigated using the positive‐up–negative‐down technique. These contributions are quantified and discussed. Furthermore, fatigue endurance has been examined by repeated switching cycles. Increase in polarization increases is associated with the improved crystallinity and enhancement of the β‐phase. However, a higher degree of crystallinity, for extended numbers of repeated cycles of the bipolar electric field, resulted in degradation of the (switching) polarization. Fatigue significantly affects the leakage and ferroelectric components while the paraelectric contribution remains almost constant. The underlying mechanism of such trends are discussed in terms of hysteresis losses. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

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

This paper introduces an innovative sandwich-structured piezoelectric nanogenerator film. In contrast to conventional piezoelectric generators, it exhibits enhanced flexibility and generates higher voltage. It can function as a self-sustaining power source for wearable sensors. To augment the film's β-phase content, consequently boosting the nanogenerator's voltage output, the nanofilm was manufactured through high-voltage electrospinning in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), incorporating stannic oxide nanoparticles (SnO2NPS) and graphene (GR).The relationship between the surface morphology, β-phase content, and voltage output performance of composite piezoelectric films with distinct compositions was comprehensively assessed and scrutinized utilizing scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, and vibration platforms. The findings reveal that the composition of 12% P(VDF-TrFE) + 5% SnO2NPS + 0.1% GR yields the finest fiber alignment, the highest β-phase content, as well as peak open-circuit voltage and short-circuit peak current values of 22.43 V and 12.95 μA, respectively. This signifies a 1.5-fold and 1.3-fold improvement compared to the film containing only SnO2NPS, and a 2.43-fold and 1.92-fold enhancement relative to the pure P(VDF-TrFE) film. Consequently, it achieves a maximum instantaneous output power of 64.578 μW. Securing the nanogenerator with the aforementioned composition to the sole of a shoe and running for 21 minutes can charge the capacitor to 4 V, thereby empowering it to operate commercial liquid crystal thermometers or approximately 80 LED lights for approximately 1.6 seconds. This technology possesses substantial significance within the realm of self-sustaining low-power electronic devices. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)) has promising potential applications in radio-frequency filters due to their excellent piezoelectric properties, flexibility, and stability. In this paper, a flexible film bulk acoustic wave filter is investigated based on P(VDF-TrFE) as piezoelectric film. A new method based on three-step annealing is developed to efficiently remove the porosity inside the P(VDF-TrFE) films so as to improve its properties. The obtained film achieved high β-phase content beyond 80% and a high piezoelectric coefficient of 27.75 pm/V. Based on the low porosity β-phase films, a flexible wide-band RF filter is designed, which consists of a bulk acoustic wave resonator and lumped inductor-capacitor elements as a hybrid configuration. The resonator sets the filter's center frequency, while the lumped LC-based matching network extends the bandwidth and enhances out-of-band rejection. The testing results of the proposed wide-band filter show its good performance, with 12.5% fractional bandwidth and an insertion loss of 3.1 dB. To verify the possibility of folding and stacking the flexible bulk acoustic wave devices for high-density multi-filter integration in MIMO communication, bending tests of the filter are also conducted with the bending strain range up to 5500 με. The testing results show no noticeable performance degradation after four bending cycles. This work demonstrates the potential of β-phase P(VDF-TrFE) bulk acoustic wave filters to expand the scope of future flexible radio-frequency filter applications. [ABSTRACT FROM AUTHOR]

A piezoelectric nanogenerator (PENG) from thin poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) polymer fiber films synthesized by the electrospinning method demonstrated the enhanced output. The β-phase content in thin films that is essential for piezo responses in polymers was analyzed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) imaging. The results showed an extremely high 92,8% of β-phase content in P(VDF-TrFE) thin films. The fabricated PENG device using P(VDF-TrFE) film demonstrated an outstanding peak-to-peak open-circuit voltage (Voc) of ∼25 V and short-circuit current (Isc) of 0.3 μA under 3 N applied force. The device could produce a maximum power density of ∼125 nW cm −2 under a 6 N load. The maximum voltage of ∼100 V was achieved with the compressive force of 20 N. Moreover, the ability to charge 0.1 μF capacity to ∼6.5 V within 180 sec was demonstrated under an external load of 6 N at 5 Hz. It can be concluded that the improved piezoelectric performance of PENG was achieved due to high β-phase content and the optimized synthesis route. The obtained electrical performance of PENG demonstrated its potential for powering low-power electronic devices by scavenging mechanical energy.

Films of piezoelectric poly(vinylidene fluoride) (PVDF) and its copolymer P(VDF-TrFE) have been studied intensively for their potential application in piezoelectric sensing devices. The present work focuses on tuning the piezoelectric properties of P(VDF-TrFE) films via incorporating Ag and polydopamine co-decorated PZT (Ag@PDA@PZT) particles. Ag@PDA@PZT particles can effectively improve the β-phase content and piezoelectric properties of P(VDF-TrFE) films. The highest open-circuit voltage and short-circuit current of P(VDF-TrFE)-based flexible pressure sensors incorporating Ag@PDA@PZT particles are ~30 V and ~2.4 μA, respectively. The flexible sensors exhibit a response to different body movements, providing a practical and potentially useful basis for human−machine interface applications.

A self-sustainable power supply function with flexibility, mechanical stability, and lightweight quality is among the required properties for pressure sensors and other low-power-consuming electronics and wearable devices. In this work, a poly(vinylidene fluoride-trifluoroethylene)/multi-walled carbon nanotube (P(VDF–TrFE)/MWCNT) composite was prepared to increase the electrical conductivity of the piezoelectric polymer and, thus, improve its electrical power generation capabilities. It was soaked by injection molding through an anodic aluminum oxide membrane to align vertically with the dipoles and exclude the possibility of dipole moment quenching. The composite membrane-type element exhibited an excellent piezoelectric coefficient d33 of 42 pC/N at a frequency of 50 Hz and an applied force intensity of 10 N, while the sensitivity was ~375 µV/g, which is favorable for self-powered pressure sensor application. The resulting composite element was utilized to generate the piezoelectric signal and to investigate the dependence of the electromechanical behavior on the surface roughness, morphology, and contact interface resistance. [ABSTRACT FROM AUTHOR]

Excitons in semiconductors are a potential alternative to charge for manipulation and storage of information. The reduced electrostatic screening in monolayers of two-dimensional (2D) semiconductors increases the binding energies of delocalized (free) excitons, while also encouraging the formation of defect-bound excitons that can be leveraged in devices for neuromorphic and quantum computing. We report the nonvolatile modulation of light emission from delocalized and defect-bound excitons in monolayer MoS2 using the remnant polarization of P-(VDF-TrFE) ferroelectric polymer islands. Photoluminescence emission intensities of delocalized excitons at room-temperature and bound excitons at cryogenic temperatures are enhanced by polarization that depletes free electrons and reduces Coulomb screening. The opposite polarization suppresses emission, providing a simple means of electrically encoding and optically reading information. Two distinct defect-bound exciton bands are identified by their spectral positions and their distinct variations with temperature and polarization, suggesting that they have distinct origins or interactions with the surrounding environment. The selective reconfiguration of free and bound excitonic emission suggests a novel device scheme toward electrically reconfigurable, optically accessible optical memory devices. [ABSTRACT FROM AUTHOR]

A lead‐free tetragonal‐phase (Ba0.94Ca0.06)(Ti0.95Zr0.05)O3 (BCTZ) micro sheet is prepared by molten‐salt growth method, which exhibits a polarizing behavior of relaxor ferroelectricity and possesses a high dielectric constant (εr) of ~2400. Subsequently, the BCTZ sheet is evenly doped into ferroelectric copolymer P(VDF‐TrFE)55/45 mol% with different mass fractions, and the flexible BCTZ/P(VDF‐TrFE) composite films are prepared using a conventional solution casting process. εr of BCTZ/P(VDF‐TrFE) increases with the mass content of BCTZ, and reaches 23.8 in 20 wt% BCTZ sample. Meanwhile, at a high electrical field of 30 MV/m, the strain and electric field of BCTZ/P(VDF‐TrFE) are in the opposite direction, indicating a negative value of piezoelectric strain coefficient (d33) caused by inverse piezoelectric effect. In addition, d33 of different BCTZ/P(VDF‐TrFE) films are fitted using a strain‐electrical field curve, which firstly increases and then decreases with increases in BCTZ content. As such, a high d33 of −47.3 pC/N is obtained in BCTZ/P(VDF‐TrFE)15/85 wt% film. Thus, this research concerning the inverse piezoelectric effect may provide a reference for designing a piezoelectric composite using in transducers and actuators. [ABSTRACT FROM AUTHOR]

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

The solar‐only response nature limits the luminescent solar concentrators (LSCs) to solar harvesting rather than responding to other stimuli, which restricts the role of LSCs to energy supply in self‐powered internet of things (IoT) systems, and the application potential of LSCs in self‐powered devices has been seriously overlooked. In this work, LSCs with photovoltaic and piezoelectric features are proposed for the first time, extending the application scenario of LSCs to self‐powered sensors with pressure responsiveness. The luminescent layer of perovskite‐polymer composite film is prepared via in situ blade coating with the piezoelectric polymer matrix of poly(vinylidenefluoride‐trifluoroethylene) (P(VDF‐TrFE)). P(VDF‐TrFE) possesses stronger DMF adsorption capacity and higher electroactive phase content than a conventional piezoelectric matrix of poly(vinylidene fluoride) (PVDF), which not only reduces the residual‐solvent‐induced defects in perovskite luminophores, but also brings a sensitive pressure response to LSCs. The dual‐functional LSCs achieve a power conversion efficiency of 1.01% and a output piezoelectric voltage of 0.95 V can be obtained even at a low pressure of 0.16 kPa. A self‐powered speed measurement system is demonstrated, and the actual speed measurement is carried out. Such dual‐functional LSCs show great potential in self‐powered electrical devices, which can be applied to low‐energy‐consumption IoT systems and other commercial smart home products. [ABSTRACT FROM AUTHOR]

Vinylidene fluoride-trifluoroethylene copolymer films of molar ratio 70/30 with thickness of about 1 μ m have been deposited from solution in ethyl methyl ketone to a glass substrate with an aluminum electrode by spin coating. The solution has been filtrated through a PTFE membrane filter with pore size 0.2 μ m directly before spin coating or it has been used as is (unfiltrated). After deposition of a top electrode, the samples have been polarized by hysteresis loops with an electric field amplitude of about 100 V/ μ m. In samples, annealed at temperature 145 ∘ C for 3 h, a high remanent polarization of about 7.5 μ C/cm2 has been achieved, without significant differences between samples fabricated of filtrated or unfiltrated solution. Spherulitic lamella are growing in films fabricated of filtrated solution when they are heated above the melting temperature to 159 ∘ C for 3 min before the further annealing process at 145 ∘ C. These films show substantially lower remanent polarization below 4 μ C/cm2. Pyroelectric images recorded with a pyroelectric laser scanning microscope show that the spherulites have very small pyroelectric activity, i.e., the spherulites consist of flat-on lamella. In contrast, no spherulitic lamella are growing in films fabricated of unfiltrated solution heated above the melting temperature, melted and annealed under the same conditions. An explanation for this observation is that filtrating changes the structure of the copolymer in solution from polymer coil to rod. Copolymer rods deposited on a substrate will crystallize in flat-on lamella when heated above the melting temperature, in contrast to copolymer coils which crystallize in edge-on lamella. [ABSTRACT FROM AUTHOR]

This study considers a fabrication of magnetoactive scaffolds based on a copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) and 5, 10, and 15 wt.% of magnetite (Fe3O4) nanoparticles modified with citric (CA) and oleic (OA) acids by solution electrospinning. The synthesized Fe3O4-CA and Fe3O4-OA nanoparticles are similar in particle size and phase composition, but differ in zeta potential values and magnetic properties. Pure P(VDF-TrFE) scaffolds as well as composites with Fe3O4-CA and Fe3O4-OA nanoparticles demonstrate beads-free 1 μm fibers. According to scanning electron (SEM) and transmission electron (TEM) microscopy, fabricated P(VDF-TrFE) scaffolds filled with CA-modified Fe3O4 nanoparticles have a more homogeneous distribution of magnetic filler due to both the high stabilization ability of CA molecules and the affinity of Fe3O4-CA nanoparticles to the solvent used and P(VDF-TrFE) functional groups. The phase composition of pure and composite scaffolds includes a predominant piezoelectric β-phase, and a γ-phase, to a lesser extent. When adding Fe3O4-CA and Fe3O4-OA nanoparticles, there was no significant decrease in the degree of crystallinity of the P(VDF-TrFE), which, on the contrary, increased up to 76% in the case of composite scaffolds loaded with 15 wt.% of the magnetic fillers. Magnetic properties, mainly saturation magnetization (Ms), are in a good agreement with the content of Fe3O4 nanoparticles and show, among the known magnetoactive PVDF or P(VDF-TrFE) scaffolds, the highest Ms value, equal to 10.0 emu/g in the case of P(VDF-TrFE) composite with 15 wt.% of Fe3O4-CA nanoparticles. [ABSTRACT FROM AUTHOR]

Nonhazardous and self-powered flexible pressure sensors based on piezoelectric effect are promising in the field of health monitoring, human-machine interfaces, soft robots and so on. Here, lead-free self-powered flexible pressure sensors with coaxial nanofiber structure are prepared, where Nb 2 CT x doped poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and BaTiO 3 (BTO) doped P(VDF-TrFE) are core and shell, respectively. Impressive piezoelectric output of ∼28 V and ∼8.2 μA was obtained for the device prepared by the nanofiber membranes under repeated mechanical force of 25 N at a frequency of 2 Hz. More importantly, the assembled self-powered pressure sensor possesses an ultrafast response time of 215 μs and a good linear relation between voltage and pressure. An interfacial polarization model based on the coaxial nanofibers has been proposed, in which the charge density calculation was carried out to understand the enhanced piezoelectric output of the piezoelectric pressure sensors. Moreover, the sensors are sensitive to various human motions and are suitable for movement monitoring. [ABSTRACT FROM AUTHOR]

In this article, a piezoelectric thin film was obtained by mixing polyvinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE)) and barium titanate (BTO) via a solvent vaporization process. All the morphologies, crystal phases, thermal and electrical tests, as well as potential simulations by COMSOL, were studied to analyze sample performances. It has been demonstrated that BTO has a positive effect on increasing the piezoelectric functional phase‐β phase within P(VDF‐TrFE). Furthermore, the optimal ratio of BTO to P(VDF‐TrFE) was determined to be 10 wt%. BTO nanoparticles were evenly distributed in the P(VDF‐TrFE) substrate, forming a more directional structure. Based on the most suitable material composition, piezoelectric, and triboelectric nanogenerators were constructed to harvest mechanical energy from human motions. Moreover, the factors influencing the electrical outputs of nanogenerators were systematically studied, such as the force values and frequencies of excitation, as well as the piezoelectric layer materials. The applications of lighting LEDs highlighted the practical use in everyday life. Finally, the comparison between simulations, theoretical analysis, and experimental results demonstrated the effect of BTO in enhancing the overall material properties. This work expands the application potential of piezoelectric nanocomposites in energy collection and storage by designing and optimizing ceramic‐doped piezoelectric polymer composites. [ABSTRACT FROM AUTHOR]

Piezoelectric materials represent a great alternative to power small electronic devices with a lower environmental impact than conventional power sources. Despite significant progress on the subject, most studies focus on energy harvesting from vibrating systems. Other publications focus on the design of the piezoelectric devices, but they are hardly comparable in terms of the amount of energy collected. In this paper a new method is presented to quantitatively characterize piezoelectric energy harvesters under a single mechanical impact using a custom Charpy‐like test bench. The method is illustrated by studying screen‐printed piezoelectric thin films of poly(vinylidenefluoride‐co‐trifluoroethylene) P(VDF‐TrFE), with different substrates acting as mechanical support. Devices printed on stretchable substrates allowing large deformation lead to overall better energy harvesting performance. However it is also demonstrated that the nature of the substrate influences the material properties of the piezoelectric film despite identical fabrication process. [ABSTRACT FROM AUTHOR]

Vinylidene fluoride-trifluoroethylene copolymer films of molar ratio 70/30 with thickness of about 1 [Formula: see text]m have been deposited from solution in ethyl methyl ketone to a glass substrate with an aluminum electrode by spin coating. The solution has been filtrated through a PTFE membrane filter with pore size 0.2 [Formula: see text]m directly before spin coating or it has been used as is (unfiltrated). After deposition of a top electrode, the samples have been polarized by hysteresis loops with an electric field amplitude of about 100 V/[Formula: see text]m. In samples, annealed at temperature 145[Formula: see text]C for 3 h, a high remanent polarization of about 7.5 [Formula: see text]C/cm2 has been achieved, without significant differences between samples fabricated of filtrated or unfiltrated solution. Spherulitic lamella are growing in films fabricated of filtrated solution when they are heated above the melting temperature to 159[Formula: see text]C for 3 min before the further annealing process at 145[Formula: see text]C. These films show substantially lower remanent polarization below 4 [Formula: see text]C/cm2. Pyroelectric images recorded with a pyroelectric laser scanning microscope show that the spherulites have very small pyroelectric activity, i.e., the spherulites consist of flat-on lamella. In contrast, no spherulitic lamella are growing in films fabricated of unfiltrated solution heated above the melting temperature, melted and annealed under the same conditions. An explanation for this observation is that filtrating changes the structure of the copolymer in solution from polymer coil to rod. Copolymer rods deposited on a substrate will crystallize in flat-on lamella when heated above the melting temperature, in contrast to copolymer coils which crystallize in edge-on lamella.

Abstract Analog storage through synaptic weights using conductance in resistive neuromorphic systems and devices inevitably generates harmful heat dissipation. This thermal issue not only limits the energy efficiency but also hampers the very‐large‐scale and highly complicated hardware integration as in the human brain. Here we demonstrate that the synaptic weights can be simulated by reconfigurable non‐volatile capacitances of a ferroelectric‐based memcapacitor with ultralow‐power consumption. The as‐designed metal/ferroelectric/metal/insulator/semiconductor memcapacitor shows distinct 3‐bit capacitance states controlled by the ferroelectric domain dynamics. These robust memcapacitive states exhibit uniform maintenance of more than 104 s and well endurance of 109 cycles. In a wired memcapacitor crossbar network hardware, analog vector‐matrix multiplication is successfully implemented to classify 9‐pixel images by collecting the sum of displacement currents (I = C × dV/dt) in each column, which intrinsically consumes zero energy in memcapacitors themselves. Our work sheds light on an ultralow‐power neural hardware based on ferroelectric memcapacitors.

We investigated the effect of gate bias stress (GBS) on the electrical characteristics of ferroelectric oxide thin-film transistors (FeOxTFTs) with poly(vinylidenefluoride-trifluoroethylene). Generally, conventional oxide thin-film transistors (OxTFTs) with dielectric gate insulators exhibit a small negative shift under negative gate bias stress (NBS) and a large positive shift under positive gate bias stress (PBS) in transfer characteristic curves. In contrast, the FeOxTFTs show a small positive shift and a large negative shift under NBS and PBS, respectively. It was confirmed that sufficient changes in the electrical characteristics are obtained by 10 min NBS and PBS. The changed electrical characteristics such as threshold voltage shift, memory on- and memory off-current were maintained for more than 168 h after NBS and 24 h after PBS. It is deduced that, since the dipole alignment of the ferroelectric layer is maximized during GBS, these changes in electrical properties are caused by the remnant dipole moments still being retained during the gate sweep. The memory on- and memory off-current are controlled by GBS and the best on/off current ratio at 107 was obtained after NBS. By repeatedly alternating NBS and PBS, the electrical characteristics were reversibly changed. Our results provide the scientific and technological basis for the development of stability and performance optimization of FeOxTFTs. [ABSTRACT FROM AUTHOR]

Small-scale energy harvesting to power self-powered electronic devices is tremendously increasing. In this context, the ability to combine thermal and mechanical energy harvesting using smart materials deserves more attention for further study. We have presented the feasibility of using P(VDF-TrFE) piezoelectric polymer coupled with NiTi shape memory alloy (SMA) to harvest both mechanical and thermal energy in simple scalable devices. A novel hybrid composite consisting of SMA, and P(VDF-TrFE) has been developed without any complex composites or patterned structures, which couples the piezoelectric effect of the poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) and the shape memory effects of NiTi SMA. We have also fabricated a multi-layer SMA/PEN/P(VDF-TrFE) device using epoxy as an interface and bonding layer. During bending, the P(VDF-TrFE) device with an active area of 3.68 cm2 generated an output voltage of 8 V and an output power of 6.25 µW. When coupled with NiTi SMA to create a hybrid composite thermoelectric material, the device can convert the phase change associated with SMA, and thus thermal energy is converted to mechanical energy and finally into electrical energy. The SMA/P(VDF-TrFE) hybrid composite produced an output voltage of ∼2 V for one cyclic heating and cooling of the device. This is a promising approach for the further development of coupled hybrid energy harvester devices for the powering of small-scale electronic devices such as sensors, MEMS, or biomedical devices. [ABSTRACT FROM AUTHOR]

Converting mechanical energy from either the ambient environment or the human body motions to the useful electrical energy will revolutionize power solutions for flexible electronics. Here, a hybrid energy harvesting strategy is reported, which combines porous polymeric piezoelectric film with an electrostatic layer as an integration for converting the mechanical energy into electrical energy. The piezoelectric materials through engineered microstructures are developed to enhance energy generation due to the higher compressibility and larger surface contact area. The electrostatic effect from the charged layer further contributes to the generation of electrical charges. By directly coating the stretchable carbon nanotubes onto the elastomers, more intimate integration of the hybrid energy harvesters enables the designs for complex electronics. Such flexible hybrid piezoelectric‐electrostatic device exhibits superior energy harvesting performance with a voltage output of 1.95 V, which improves 30% and 100% compared to the electrostatic and piezoelectric alone device, respectively. Experiments are also performed to demonstrate the implementation of the hybrid device's energy conversion to power small electronics and recognition of different body motions. Such hybrid strategy provides a new solution toward future energy revolution for flexible electronics. [ABSTRACT FROM AUTHOR]

In this study we fabricated a piezoelectric nanogenerator (PENG) of nanocomposite thin film comprising a conductive nanofiller of reduced graphene oxide (rGO) dispersed in a poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) matrix that was anticipated to show enhanced energy harvest performance. For the film preparation we employed the Langmuir-Schaefer (LS) technique to provide direct nucleation of the polar β-phase without any traditional polling or annealing process. We prepared five PENGs consisting of the nanocomposite LS films with different rGO contents in the P(VDF-TrFE) matrix and optimized their energy harvest performance. We found that the rGO-0.002 wt% film yielded the highest peak-peak open-circuit voltage (VOC) of 88 V upon bending and releasing at 2.5 Hz frequency, which was more than two times higher than the pristine P(VDF-TrFE) film. This optimized performance was explained by increased β-phase content, crystallinity, and piezoelectric modulus, and improved dielectric properties, based on scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), x-ray diffraction (XRD), piezoelectric modulus, and dielectric property measurement results. This PENG with enhanced energy harvest performance has great potential in practical applications for low energy power supply in microelectronics such as wearable devices. [ABSTRACT FROM AUTHOR]

P(VDF-TrFE) is a promising material for flexible acoustic devices owing to its good piezoelectric performance and excellent stretchability. However, the high density of internal pores and large surface roughness of the conventional P(VDF-TrFE) results in a high propagation attenuation for acoustic waves, which limits its use in flexible acoustic devices. In this paper, a novel method based on two-step annealing is proposed to effectively remove the pores inside the P(VDF-TrFE) film and reduce its surface roughness. The obtained P(VDF-TrFE) film possesses excellent characteristics, including a high breakdown strength of >300 kV/mm, a high-purity β-phase content of more than 80%, and high piezoelectric coefficients (d33) of 42 pm/V. Based on the low-porosity β-phase P(VDF-TrFE) film, we fabricated flexible film bulk acoustic resonators (FBARs) which exhibit high sharp resonance peaks. The pressure sensor was made by sandwiching the FBARs with two PDMS microneedle patches. Heartbeat and respiration rate monitoring were achieved using the pressure sensor. This work demonstrates the feasibility of high-performance flexible piezoelectric acoustic resonators based on low-porosity P(VDF-TrFE) films, which could see wider applications in the wearable sensors for both physical and chemical sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-steps annealing was applied to P(VDF-TrFE) fiber mats for highcrystallinity and large ferroelectric domain structures; • High piezoelectricity was achieved by non-contact corona poling in the high-κwater medium; • The dimensional effect induced significant polarization changes and highpiezoelectricity. Polymer piezoelectrics hold great potential for energy harvesting and wearable electronics. Efforts have been dedicated to enhancing piezoelectric coefficients and thermostability for several decades, but most of these have not been successful. In this report, we demonstrate a straightforward way to achieve high piezoelectric coefficients and output voltages while maintaining high thermostability at temperatures over 110 °C. Poly(vinylidene fluoride- co -trifluoroethylene) [P(VDF-TrFE)] 80/20 mol.% nanofiber mats (made by electrospinning) with extremely high crystallinity and Curie temperatures were obtained via a two-step annealing process, from which large ferroelectric domains were formed in extended-chain crystals. After corona poling using water, which is a high dielectric constant medium, giant piezoelectricity (apparent d 33 = 1045 ± 20 pC/N) and high output voltages (29.9 ± 0.5 V) were achieved. It is found that the dimensional effect induced significant polarization changes, which is the key requirement for piezoelectricity. Our finding in this work paves a way to further improve high-performance polymer piezoelectrics. [ABSTRACT FROM AUTHOR]

• TiO 2 -NFs-doped P(VDF-TrFE) films are treated by ultraviolet-assisted-thermal annealing. • High power density of 35 mW/m2 with superior UV-detection capability of PENGs is realized. • A circuit is designed to perform stepping illumination of LEDs under tapping on UV photodetectors. • A real-time outdoor UV index is provided via self-powered piezoelectric UV photodetectors. Ultraviolet (UV) radiation overexposure due to severe ozone layer depletion increases the risk of skin cancer. However, the traditional UV index meter needs the power supply which is not convenient for outdoor use. The study aims to develop a UV overexposure warning system with a self-powered piezoelectric UV photodetector to provide a real-time UV index. A self-powered piezoelectric UV photodetector with TiO 2 -nanofibers (TiO 2 -NFs)-doped poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) nanocomposite films via ultraviolet-assisted thermal annealing was fabricated. A lumped circuit was designed to realize the stepping illumination of light-emitting diodes (LEDs) under continuous tapping of self-powered piezoelectric UV photodetectors. At a fixed 40-kPa pressure and 2-Hz frequency with varying UV irradiation power densities, the self-powered piezoelectric UV photodetectors exhibited outstanding UV detection capabilities, with a responsivity and detectivity for 0.14 mA/W and 4 × 108 Jones, respectively. A UV overexposure warning system was established by connecting a self-powered piezoelectric UV photodetector with a lumped circuit to achieve the stepping illumination of LEDs under continuous tapping, giving warnings for those performing outdoor activities to avoid UV overexposure. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ferro-PI film is composed of P(VDF-TrFE) copolymer and homogeneous polyimide. • PDLCs are sandwiched between the Ferro-PI films. • Ferro-PI films increase the effective voltage drop across the PDLCs. • Ferro-PI films promise PDLCs with a low voltage, high contrast, and wide view angle. Smart windows incorporating polymer dispersed liquid crystal (PDLC) technology provide user-friendly operation and play a significant role in intelligent buildings and building energy conservation. Long standing issues of the PDLCs such as high driving voltage, low contrast ratio, and narrow viewing angle hinder their applications. Here PDLCs are sandwiched between the hybrid substrates composed of the ferroelectric polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) copolymer and the homogeneous polyimide. The high dielectric constant and ion-trapping ability of ferroelectric copolymers increase the effective voltage drop in the PDLCs. Concurrently, the local electric field created by large dipole moment of ferroelectric copolymers triggers the alignment of liquid crystals (LCs) along the applied field. These synergistic effects contribute to a substantial decrease in the driving voltage of PDLCs. In the opaque state, the random dipole moments in ferroelectric copolymers disrupt the LC orientations near hybrid substrates, thereby increasing the light scattering and reducing the transmission of PDLCs. Consequently, the proposed PDLCs exhibit a contrast ratio ∼2× higher compared to the conventional PDLCs at normal incident. Moreover, the proposed PDLCs demonstrate a wider viewing angle in the transparent state compared to conventional PDLCs. This development promises energy-efficient, eco-friendly, and cost-effective smart windows. [ABSTRACT FROM AUTHOR]

• Microwave annealing was both time and energy saving for P(VDF-TrFE) fabrication. • Microwave annealed films presented remanent polarization of 0.09 C m-2 and d 33 coefficient of 28 pC N-1. • Microwave treated devices were developed for monitoring of human physiological activities and proximity perception. Multifunctional electronic skins have attracted considerable attention for applications in robotics, health monitoring and human–machine interfaces. Ferroelectric polymers, especially poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), are one of the most promising materials to construct multifunctional electronic skins due to their exceptional flexibility and piezoelectric and pyroelectric properties. Post annealing treatment is required to enhance crystallization and thus electroactivity of P(VDF-TrFE) films, which usually is both time and energy consuming. Here we developed a rapid microwave annealing (MWA) process which significantly reduced annealing period from several hours to several minutes. AN MWA-treated and 2 μm thick P(VDF-TrFE) film achieved remanent polarization of 0.09C m−2 and piezoelectric d 33 coefficient of 28 pC N−1. MWA-treated copolymer films were further encapsulated by PDMS elastomer for further enhanced d 33 coefficient up to 49 pC N−1. This kind of MWA-treated devices were developed for monitoring of human physiological activities, including neck movements, coughing and pulsation, and proximity perception of hot targets for early warning of low-temperature scalds. All these observations indicate that MWA is a feasible and efficient measure to fabricate high-performance ferroelectric copolymer devices for multifunctional perception. [ABSTRACT FROM AUTHOR]

Flexible magnetoelectric (ME) polymer-based generators have attracted increasing attention in the energy harvesting field based on the ME coupling effect. However, a large ME coupling response and high conversion performance are highly desirable. In line with this, a three-phase hierarchy configuration composite with enhanced ME response of BaTiO 3 (BT), Ni 0.8 Zn 0.2 Fe 2 O 4 (NZFO), and P(VDF-TrFE) polymer as a free-standing film is prepared, in which a tiny volume fraction of BT nanoparticles is hierarchically deposited in a NZFO embedded in P(VDF-TrFE) matrix. A systematic study of structural, morphological, dielectric, ferroelectric, piezoelectric, and ME properties has been carried out. Compared with the particulate composite, the piezoelectric, ferroelectric, and ME interaction of the hierarchy composite are improved. A large ME coupling coefficient of 92.99 mV/cm·Oe was achieved, which is 1.4 times as large as that of the particulate composite (65.82 mV/cm·Oe). Further, the versatility of this ME composite is demonstrated in a magnetic energy harvesting application. The designed flexible ME composite offers a promising application for the realization of an efficient ME energy harvester to power portable electronic devices. • A three-phase hierarchy flexible composite with enhanced ME response is prepared. • The hierarchy flexible composite deliveries a ME coefficient 1.4 times as high as the particulate composite. • The versatility of hierarchy ME composite is demonstrated in a magnetic energy harvesting application. [ABSTRACT FROM AUTHOR]

The electromechanical properties of PVDF-based polymers, namely converting electrical into mechanical energy, are mainly decided by the crystal structure and domain size of the target product. Thus, we prepare the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), its terpolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), and tetrapolymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene -hexafluoropropylene) (P(VDF-TrFE-CFE-HFP)) films for comparison, respectively, where the role of the introduction of third and fourth monomers in the electromechanical properties of P(VDF-TrFE) is completely disclosed. Because of introducing CFE and HFP monomers, P(VDF-TrFE) with the ferroelectricity has converted into the relaxor ferroelectric P(VDF-TrFE-CFE-HFP) with a slimmer P-E loop while maintaining good maximum polarization (P m). Since the nano ferroelectric domains in the relaxor ferroelectric material are easy to reverse along the polarizing electric field, The P(VDF-TrFE-CFE-HFP) sample achieved a dielectric constant (ε r) of ∼29 and a strain in the thickness direction (S 33) of ∼ -5%, respectively, while the ε r and S 33 of P(VDF-TrFE) sample are ∼11 and ∼-0.8 %, respectively. This research indicates the availability of the third and fourth monomers for improving the electromechanical effect of such electrostrictive polymers, having wide applications in flexible actuators, transformers, sensors, and so forth. In this work, we developed a P(VDF-TrFE-CFE-HFP) tetrapolymer by introducing a small amount of hexafluoropropylene (HFP) into P(VDF-TrFE-CFE). A high dielectric constant (ε r) of ∼29 and a strain in the thickness direction of ∼ -5% are obtained in the P(VDF-TrFE-CFE-HFP) sample, respectively, which is higher than that of the P(VDF-TrFE) sample (∼11 and ∼-0.8 %). [Display omitted] • P(VDF-TrFE-CFE-HFP) film sample was fabricated by the solution-casting method. • The HFP monomer could enable the polymer with the relaxor ferroelectricity to keep high maximum polarization. • A dielectric constant (ε r) of ∼29 and an electrostriction (S 33) of ∼-5% are obtained in P(VDF-TrFE-CFE-HFP). [ABSTRACT FROM AUTHOR]

Piezoelectric polymers are a class of material that belong to carbon–hydrogen-based organic materials with a long polymer chain. They fill the void where single crystals and ceramics fail to perform. This characteristic of piezoelectric polymers made them unique. Their piezoelectric stress constant is higher than ceramics and the piezoelectric strain is lower compared to ceramics. This study’s goal is to present the most recent information on poly(vinylidene fluoride) with trifluoroethylene P(VDF-TrFE), a major copolymer of poly(vinylidene fluoride) PVDF with piezoelectric, pyroelectric, and ferroelectric characteristics. The fabrication of P(VDF-TrFE) composites and their usage in a variety of applications, including in actuators, transducers, generators, and energy harvesting, are the primary topics of this work. The report provides an analysis of how the addition of fillers improves some of the features of P(VDF-TrFE). Commonly utilized polymer composite preparation techniques, including spinning, Langmuir–Blodgett (LB), solution casting, melt extrusion, and electrospinning are described, along with their effects on the pertinent characteristics of the polymer composite. A brief discussion on the literature related to different applications (such as bio-electronic devices, sensors and high energy-density piezoelectric generators, low mechanical damping, and easy voltage rectifiers of the polymer composite is also presented.

A self-sustainable power supply function with flexibility, mechanical stability, and lightweight quality is among the required properties for pressure sensors and other low-power-consuming electronics and wearable devices. In this work, a poly(vinylidene fluoride-trifluoroethylene)/multi-walled carbon nanotube (P(VDF–TrFE)/MWCNT) composite was prepared to increase the electrical conductivity of the piezoelectric polymer and, thus, improve its electrical power generation capabilities. It was soaked by injection molding through an anodic aluminum oxide membrane to align vertically with the dipoles and exclude the possibility of dipole moment quenching. The composite membrane-type element exhibited an excellent piezoelectric coefficient d33 of 42 pC/N at a frequency of 50 Hz and an applied force intensity of 10 N, while the sensitivity was ~375 µV/g, which is favorable for self-powered pressure sensor application. The resulting composite element was utilized to generate the piezoelectric signal and to investigate the dependence of the electromechanical behavior on the surface roughness, morphology, and contact interface resistance.

Abstract Converting mechanical energy from either the ambient environment or the human body motions to the useful electrical energy will revolutionize power solutions for flexible electronics. Here, a hybrid energy harvesting strategy is reported, which combines porous polymeric piezoelectric film with an electrostatic layer as an integration for converting the mechanical energy into electrical energy. The piezoelectric materials through engineered microstructures are developed to enhance energy generation due to the higher compressibility and larger surface contact area. The electrostatic effect from the charged layer further contributes to the generation of electrical charges. By directly coating the stretchable carbon nanotubes onto the elastomers, more intimate integration of the hybrid energy harvesters enables the designs for complex electronics. Such flexible hybrid piezoelectric‐electrostatic device exhibits superior energy harvesting performance with a voltage output of 1.95 V, which improves 30% and 100% compared to the electrostatic and piezoelectric alone device, respectively. Experiments are also performed to demonstrate the implementation of the hybrid device's energy conversion to power small electronics and recognition of different body motions. Such hybrid strategy provides a new solution toward future energy revolution for flexible electronics.

Abstract Ferroelectric materials with switchable electrical polarization have been widely used in tunnel junctions, non‐volatile memories, and field‐effect transistors. Large‐area organic ferroelectric polymers compatible with silicon or flexible substrates have played a crucial role in nanoelectronics. Poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE) as a representative, different from traditional bulk oxide ferroelectrics in terms of atom arrangements and fabrication methods, has frequently been used as the ferroelectric gate for high‐performance electronic, optical, and synaptic transistors. Ferroelectric copolymers have gradually become a promising and versatile alternative for inorganic ferroelectrics. This review will focus on the interface engineering and device applications of 2D materials/ferroelectric P(VDF‐TrFE) hybrid structures. The intrinsic ferroelectric properties and unique features of P(VDF‐TrFE) are first elucidated. Next, typical device structures with ferroelectric gating effect followed by its physical working mechanisms will be discussed. In the next section, diverse nanoelectronics applications of ferroelectric field effect transistors based on P(VDF‐TrFE), including optoelectronic devices, non‐volatile memories, neuromorphic computing, and negative capacitance transistors, are clarified. Moreover, existing challenges and further development for ferroelectric polymer will be discussed. With an emphasis on the ferroelectric polymer gate and related issues, this review provides a timely summary of current physical understanding and progresses.

It is well thought that the performance of polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] is better than that of oriented polyvinylidene fluoride (oriented PVDF). But the harsh fabrication process or poor stability of P(VDF-TrFE) polymer limits its mass production. Therefore, it is worth making a comparative property assessment of PVDF and P(VDF-TrFE) piezoelectric polymers from the point of view of the practical application. In this work, we have used the oriented PVDF and P(VDF-TrFE) films to prepare an array of flexible piezoelectric and pyroelectric hybrid energy conversion devices. The responses of devices to different scenarios and environments were investigated. It was found that the two energy conversion devices can convert various forms of energy from the external stimulus conditions to get the output electrical signals. However, the two conversion devices exhibited different signal responses to different forms of external stimuli, which provides a reference for the choice of device materials in practical applications. It was confirmed that the oriented PVDF film fabricated by the simple and economical method has also great potential applications as wearable and electronic touch screens and medical monitoring devices. [ABSTRACT FROM AUTHOR]