PVDF Film Research Articles

Flexoelectricity on the photovoltaic and pyroelectric effect and ferroelectric memory of 3D-printed BaTiO3/PVDF nanocomposite

Ferroelectric memories show great potential in applications of portable electronics due to low power consumption, high reliability and fast response speed. Therefore, non-destructive readout of ferroelectric memories using the ferroelectric photovoltaic effect attracted tremendous research attention. In this investigation, flexoelectric-enhanced photovoltaic effect (FPV effect) were systematically investigated in curved 3D-printed BaTiO3/PVDF composite films. In the bending process, a strain gradient field was formed between the BaTiO3 (BTO) particles, which led to a relatively large flexoelectric effect. Compared with that of pristine PVDF, the flexoelectric coefficient of BTO/PVDF-15 (15% BTO) was increased 3.7-fold to 2.65 × 10−9 C/m. Furthermore, we found that the photovoltaic current Ipv of the BTO/PVDF-15 (15% BTO) composite film increased by 3.4 times compared with the pristine PVDF film at the same curvature. This is mainly attributed to the FPV effect. In addition, “polarization channels” were found for the first time inside nanocomposite materials using the flexoelectricity effect through 2D phase-field simulations, and the channels can be artificially controlled by simply bending the film. Most importantly, the BTO/PVDF-based composite film was designed as flexible ferroelectric memories. We demonstrated for the first time that the intensity difference of the signal for 0 and 1 of the BTO/PVDF-based memories were more than 10 times, which can be read directly using a laser. This investigation shows great promise that flexoelectricity in piezoelectric polymer nanocomposite can greatly benefit the nondestructive readout of ferroelectric memory devices.

Highly Stable and End‐group Tuneable Metal–Organic Framework/Polymer Composite for Superior Triboelectric Nanogenerator Application

AbstractTriboelectric nanogenerators (TENGs) are receiving significant attention lately as efficient mechanical energy harvesting devices. They are finding multiple uses in numerous low‐power applications. Current TENG designs, although innovative, fall short on practical demands like performance tunability, modulatory, and stability. This invites further research in the use of new materials for TENGs. Metal‐organic frameworks (MOFs) offer a unique feature of molecular tunability to optimize energy conversion which has been exploited in this study. Prototypal hybridization strategy is deployed on underexplored isoreticular subfamily UiO‐66(Zr) MOFs through UiO‐66‐X/PVDF (X = H or Br) composites for TENG output tuning and amplification. UiO‐66‐X/PVDF exhibits good aquatic and thermal stability accompanying substantial boost in TENG power. Functionalized H2BDC linker improved surface roughness and potential. UiO‐66‐Br encased in PVDF matrix boosted charge and TENG performance by enhancing electrification. Computational details support observations. Device captures waste energy in a vertical contact‐separation mode and functions consistently amidst diverse environmental settings. Functionalized TENG‐2 delivers a Vp–p of 110.41 V, which is 2.92 times and 14.12 times higher than unfunctionalized TENG‐1 and PVDF film, respectively. Findings reveal maiden example of ligand‐mediated functional group‐driven performance tuning of TENG and mechanistic insight using isoreticular MOFs/PVDF composites.

Highly Transparent PVDF Films with Enhanced Dielectric and Energy Storage Properties Tailored by a PMMA-co-GMA Copolymer

Highly Transparent PVDF Films with Enhanced Dielectric and Energy Storage Properties Tailored by a PMMA-co-GMA Copolymer

Control over the complex phase evolutions for ultrahigh dielectric energy storage in pure poly(vinylidene fluoride) films

Poly(vinylidene fluoride) (PVDF) is a basic polymer that has been extensively used in flexible electronics, with the properties differing in terms of multiple phases, e.g. α, β, and γ. As generally involved, processing induced phase variations have not yet been identified clearly, which furthermore often embarrasses the attributions and contributions in the properties and mechanisms. To this end, the phase compositions and evolutions in pure PVDF films are systematically tuned and explored by annealing and quenching processing. The annealed PVDF exhibits a predominant γ-phase, while α-phase is dominated in quenched PVDF. Upon the induced different phase compositions, the optimally processed PVDF films similarly exhibit an ultrahigh dielectric energy storage density e.g. 19.66 J cm−3 for annealed and 21.73 J cm−3 for quenched PVDF film, respectively, but only the former maintains a simultaneously high discharge efficiency of 65 %. With showing excellent energy storage performance, the processed especially the annealed PVDF film could compare to many existing high-performance dielectric energy storage systems. This work thus not only uncovers the phase evolutions as well as their impacts on the properties in PVDF system, but also demonstrates firstly a high energy storage performance in pure PVDF.

Membranes Based on Polyvinylidene Fluoride and Radiation-Grafted Sulfonated Polystyrene and Their Performance in Proton-Exchange Membrane Fuel Cells.

Proton-exchange membranes based on gamma-irradiated films of PVDF and radiation-grafted sulfonated polystyrene with an ion-exchange capacity of 1.8 meq/g and crosslinking degrees of 0 and 3% were synthesized. A solvent-free, environmentally friendly method of styrene grafting from its aqueous emulsion, with a styrene content of only 5 vol.% was used. Energy dispersive X-ray mapping analysis showed that the grafted sulfonated polystyrene is uniformly distributed throughout the membrane thickness. The obtained materials had a proton conductivity up to 132 mS/cm at 80 °C and a hydrogen permeability of up to 5.2 cm2/s at 30 °C, which significantly exceeded similar values for Nafion®-212 membranes. The resulting membranes exhibited a H2/O2 fuel cell peak power density of up to 0.4 W/cm2 at 65 °C. Accelerated stability tests showed that adding a crosslinking agent could significantly increase the stability of the membranes in the fuel cells. The thermal properties and crystallinity of the membranes were investigated through differential scanning calorimetry and X-ray powder diffraction methods. The conductivity, water uptake, and mechanical properties of the membranes (stress–strain curves) were also characterized.

Enhanced neuronal differentiation by dynamic piezoelectric stimulation.

Electroactive smart materials play an important role for tissue regenerative applications. Poly(vinylidene fluoride) (PVDF) is a specific subtype of piezoelectric electroactive material that generates electrical potential upon mechanical stimulation. This work focuses on the application of piezoelectric PVDF films for neural differentiation. Human neural precursor cells (hNPCs) are cultured on piezoelectric poled and non-poled β-PVDF films with or without a pre-coating step of poly-d-lysine and laminin (PDL/L). Subsequently, hNPCs differentiation into the neuronal lineage is assessed (MAP2+ and DCX+ ) under static or dynamic (piezoelectric stimulation) culture conditions. The results demonstrate that poled and coated β-PVDF films induce neuronal differentiation under static culture conditions which is further enhanced with mechanical stimulation. In silico calculations of the electrostatic potential of different domains of laminin, highlight the high polarity of those domains, which shows a clear preference to interact with the varying surface electric field of the piezoelectric material under mechanical stimulation. These interactions might explain the higher neuronal differentiation induced by poled β-PVDF films pre-coated with PDL/L under dynamic conditions. Our results suggest that electromechanical stimuli, such as the ones induced by piezoelectric β-PVDF films, are suitable to promote neuronal differentiation and hold great promise for the development of neuroregenerative therapies.

Flexible polymer-based triboelectric nanogenerator using Poly(vinylidene fluoride) and bombyx mori silk

This paper demonstrates a flexible triboelectric nanogenerator (TENG) using Poly(vinylidene fluoride) (PVDF) and silk by exploiting their inherent susceptibility for gaining and losing electrons. Bombyx mori silk possesses a strong capability of losing electrons whereas PVDF has the penchant for gaining electrons. Hence the combination of silk and PVDF could be explored as a novel and unique triboelectric pair for the fabrication of triboelectric nanogenerator. With this motivation, silk-PVDF-based TENG was fabricated on flexible substrate along with the systematic evaluation of its output performance. The primary objective of this paper is divided into two major parts. Initially, a comprehensive study was carried out to investigate the maximum output voltage of the TENG and its correlation with the morphology and composition of PVDF films. The structural optimization of the TENG was also performed in order to deduce the maximum output. Finally, various practical applications of silk-PVDF-based TENG were demonstrated. Through proper optimization, the maximum short circuit current and open circuit voltage acquired from the TENG was experimentally found out to be 11.3 μA and 611 V (peak to peak value), respectively. A relatively high output power density of 1.85 W/m2 was obtained from the optimized nanogenerator for a load resistance of 10 MΩ. The efficacy of this prototype was investigated by powering up commercial red LEDs, charging of capacitors, and harvesting energy from human body movement. The TENG is not only capable to light up 56 commercial red LED bulbs but also is able to harvest mechanical energy from body motion. The highest amount of energy was scavenged from human footsteps.

Spontaneous and Continuous Actuators Driven by Fluctuations in Ambient Humidity for Energy-Harvesting Applications.

Self-oscillating soft actuators that enable spontaneous and continuous motion under an external stimulus with no human intervention have attracted extensive attention due to the great value of the realization of more sustainable and low-power-consumption actuators. However, the achievement of such actuators that collect chemical energy from the fluctuations in ambient humidity is still a great challenge. Here, an actuator film based on spiropyran@agarose (SP@AG) that can spontaneously and continuously collect chemical energy from the fluctuations in ambient humidity is developed. It is noteworthy that the SP@AG film has excellent self-oscillation behavior and a high oscillation amplitude (184°) under the size (40 × 8 mm) or load of 116 mg (about 5.2 times of the film weight). Moreover, on the basis of the self-oscillating motion, an energy conversion device is constructed by integrating the soft actuator with a piezoelectric PVDF film, which can spontaneously and continuously generate an output voltage of about 30 mV. Finally, a proof of concept for an "intelligent light-controllable window" that can open under humidity stimulus and change color under light is proposed herein. Overall, the self-oscillating actuator driven by fluctuations in ambient humidity shows immense potential in response to the atmospheric humidity of day-night rhythm and humid-energy-harvesting devices.

Electrospun PA66/Graphene Fiber Films and Application on Flexible Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) are considered to be the most promising energy supply equipment for wearable devices, due to their excellent portability and good mechanical properties. Nevertheless, low power generation efficiency, high fabrication difficulty, and poor wearability hinder their application in the wearable field. In this work, PA66/graphene fiber films with 0, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% graphene and PVDF films were prepared by electrospinning. Meanwhile, TENGs were prepared with PA66/graphene fiber films, PVDF films and plain weave conductive cloth, which were used as the positive friction layer, negative friction layer and the flexible substrate, respectively. The results demonstrated that TENGs prepared by PA66/graphene fiber films with 2 wt% grapheme showed the best performance, and that the maximum open circuit voltage and short circuit current of TENGs could reach 180 V and 7.8 μA, respectively, and that the power density was 2.67 W/m2 when the external load was 113 MΩ. This is why the PA66/graphene film produced a more subtle secondary network with the addition of graphene, used as a charge capture site to increase its surface charge. Additionally, all the layered structures of TENGs were composed of breathable electrospun films and plain conductive cloth, with water vapor transmittance (WVT) of 9.6 Kgm−2d−1, reflecting excellent wearing comfort. The study showed that TENGs, based on all electrospinning, have great potential in the field of wearable energy supply devices.

Effect of Additive Manufacturing on β‐Phase Poly(Vinylidene Fluoride)‐Based Capacitive Temperature Sensors

Additive manufacturing, commonly known as 3D printing, significantly simplifies the manufacturing process for soft electronics. This work demonstrates the feasibility of a fully 3D-printed flexible poly(vinylidene fluoride) (PVdF) capacitive temperature sensor. The sensor is constructed using fused deposition modeling (FDM)-printed PVdF film as the dielectric (thickness ≈180–280 μm) sandwiched between two parallel Direct Ink Writing (DIW) printed silver electrodes (entire device thickness ≈200–380 μm). The motion of the nozzle can facilitate mechanical drawing to the molten PVdF filament, which is a necessary condition to increase the β-phase content (critical for the sensitivity of the sensor). With optimized printing parameters, the highest β-phase content (21.30%) is achieved when printing with a nozzle temperature of 200 °C and a print speed of 70 mm s−1. The research demonstrates the application of the device as a temperature sensor by applying heating-and-cooling cycles from room temperature (25 °C) up to 140 °C while measuring the capacitance as a function of frequency under different temperatures. The sensor exhibits a stable sensitivity of 3 pF °C−1 at 102 Hz and higher frequencies and improved sensitivities at frequencies higher than 102 Hz after dielectric polarization via the corona poling method.

Impedance studies of free-standing, flexible thin films of PVDF filled with gallium nitride nanoparticles

Impedance studies of free-standing, flexible thin films of PVDF filled with gallium nitride nanoparticles

Design and development of a high-performance tensile-mode piezoelectric energy harvester based on a three-hinged force-amplification mechanism

When considering durability and reliability, flexible piezoelectric materials, such as PVDF and macro-fiber composite, are preferable to piezoceramics due to the brittleness of piezoceramics. However, flexible piezoelectric materials cannot sustain compressive loads so they need to be operated in either tensile or bending mode. The tensile mode has the advantage of uniform strain distribution over the bending mode. This study proposes a novel tensile-mode piezoelectric energy harvester based on a three-hinged force amplification mechanism. The proposed design consists of a rigid beam and an elastic PVDF film connected to each other via a revolute joint. The assembly is attached to a base via revolute joints with the PVDF film pre-stretched. The PVDF film bears a dynamic tensile load when the harvester is under harmonic excitations. A theoretical model of the proposed harvester is developed and experimentally validated. The simulation and experimental results show that the proposed design exhibits a strong hardening effect due to the nonlinear geometry of the three-hinged mechanism. The effect of preloads and mass distributions are explored to see their impact on the harvesting performance. It is shown that the peak voltage and bandwidth of the harvester decline as the preload increases. By properly tuning the mass distribution, the performance of the harvester can be enhanced. Compared with a bending-mode cantilevered harvester, the voltage output and harvesting bandwidth of the proposed harvester can be improved by 500% and 1250%, respectively.

Study on relaxation behavior of all-polymer PVDF-based films containing dielectric fluoroelastomer

All-polymer PVDF-based films consisting of fluoroelastomer were prepared through simple hot-pressing method, which were comprehensively explored by dielectric relaxation spectroscopy with the frequency of 20–30 M Hz and the temperature from 25 °C to 205 °C. Compared with single-layered PVDF film, The permittivities of both 30% FKM/PVDF blend film and sandwich-structured FKM/PVDF film were elevated, and the values of dielectric loss and DC conductivity dramatically dropped throughout whole temperature range. The characteristic peaks of Curie transition temperature (Tc) were detected for all samples, while Tc of sandwich-structured FKM/PVDF film shifted to a higher temperature. Moreover, the results of electric modulus spectra and Cole-Cole plots revealed the non-Debye relaxation mechanism of the studied samples. Furthermore, the values of both Eτ and Eσ for FKM/PVDF films were increased compared with single-layered PVDF, with a more profound effect on sandwich-structured FKM/PVDF film. Such higher value is beneficial to restrain the relaxing and conducing behaviors Thus, sandwich-structured FKM/PVDF film will be a potential material for enhancing electric displacement and reducing the energy loss.

Poly(vinylidene fluoride) Intestinal Sleeve Implants for the Treatment of Obesity and Type 2 Diabetes.

Currently, treatment of diabetes and associated obesity involves Roux-en-Y gastric bypass or sleeve gastrectomy to reduce the absorption of nutrients from the intestine to achieve blood glucose control. However, the surgical procedure and subsequent recovery are physically and psychologically burdensome for patients, with possible side effects, so alternative treatments are being developed. In this study, two methods, solution casting and machine direction orientation (MDO), were used to prepare intestinal implants made of poly(vinylidene fluoride) (PVDF) film and implant them into the duodenum of type 2 diabetic rats for the treatment of obesity and blood glucose control. The PVDF film obtained by the MDO process was characterized by FT-IR, Raman spectroscopy, XRD and piezoelectricity tests, which showed higher composition of β crystalline phase and better elongation and mechanical strength in specific directions. Therefore, the material was finally tested on rats after it was proven to be non-toxic by biological toxicity tests. The PVDF was implanted into alloxan-induced diabetic rats, which were used as a model of impaired insulin secretion due to pancreatic beta cell destruction rather than obesity-induced diabetes, and rats were tracked for 24 days, showing significantly improved body weight and blood glucose levels. As an alternative therapeutic option, intestinal sleeve implant showed future potential for application.

High-performance lithium-ion batteries with gel polymer electrolyte based on ultra-thin PVDF film

High-performance lithium-ion batteries with gel polymer electrolyte based on ultra-thin PVDF film

Influence of Various Physiochemical Parameters of AFeO3 (A = Bi, Er, Ga, La, Sm, Y) Fillers on the Dielectric, Ferroelectric, Energy Storage, and Mechanical Energy Harvesting Performance of PVDF

AbstractDifferent filler particles are very often used by researchers all over the world to tune the dielectric, ferroelectric, piezoelectric, energy storage, and energy harvesting properties of poly(vinylidene fluoride) (PVDF). In the present work, different perovskite ferrites, AFeO3 (A = Bi, Er, Ga, La, Sm, and Y), are included into PVDF matrix separately. The roles of different parameters like, particle size, dielectric permittivity, ferroelectric polarization, crystal structure, etc. of the fillers in tuning the performance of respective PVDF‐based composites are comprehensively and simultaneously studied here. Non‐centrosymmetric fillers are found to improve the output performances of PVDF more effectively compared to that of centrosymmetric fillers. 5 wt% BiFeO3‐loaded PVDF film (5BF) shows the best performance in all aspects. Upon repeated human finger tapping, the maximum instantaneous output power density and instantaneous current across a 10 MΩ resistor connected across the 5BF film are found to be ≈3 µW cm−2 and 1.25 µA, respectively. The rectified voltage from 5BF nanogenerator is used to charge a 10 µF commercial capacitor up to ≈2.8 V and lights up some LEDs as a part of its real life applicability. The fabricated nanogenerator also shows good vibration and pressure sensing ability.

Superior energy storage of sandwiched PVDF films by separate introduction of core-shell Ag@BT nanoparticles and 2D MXene nanosheets

Polymer-based dielectrics exhibit promising applications in energy storage devices due to their enormous power density, good flexibility, and low cost. However, the low energy storage density remains to be the bottleneck. Here, sandwiched polymer-ceramic nanocomposite films are designed by stacking the PVDF middle layer incorporated Ag-decorated BaTiO3 (BT) ceramic nanoparticles (Ag@BT NPs) and the PVDF top/bottom layers embedded 2D layered MXene nanosheets. Interestingly, the optimal performances with a reversible energy storage density (Wre) as high as ∼ 22.3 J/cm3 with an efficiency η ∼ 77% at a low electric field of 270 MV/m are achieved for the film with 5 wt% DA@Ag@BT/PVDF middle layer. Strong interfacial coupling, ionic interaction, and enhanced breakdown strength due to the Coulomb blocking effect in the hierarchical structures with different fillers are responsible for the high energy storage performance. Moreover, the phase-field simulation further proved an appropriate amount of DA@Ag@BT NPs can effectively prevent the formation of the conductive network, inhibit the dielectric loss and improve the breakdown strength. This hierarchical strategy demonstrates an applicable route for fabricating polymer nanocomposites with high performance.

Preparation and Luminescence Properties of PVDF/ZnS:Mn Flexible Thin-Film Sensors

Flexible luminescent thin-film sensors have attracted widespread attention for their potential applications in biomedical detection, structural health detection, and smart wear. In this work, PVDF/ZnS:Mn flexible luminescent thin-film sensors were fabricated using electro-assisted 3D-printing techniques. The interaction and influence of PVDF thin film and ZnS:Mn were studied. The mechanism through which the PVDF matrix and ZnS:Mn particles affects the luminescence of the flexible thin-film sensor were investigated. The results demonstrate that the ZnS:Mn luminescent particles in PVDF thin films can promote the formation of the β-phase in the PVDF thin films. The mechano-luminesce spectra of the PVDF/ZnS:Mn composite thin film is consistent with the photoluminescence spectra, both of which exhibit yellow light with a wavelength of 580 nm. Mn entering the ZnS lattice increases the number of effective luminescent centres. Because of the double piezoelectric field, when the Mn content of ZnS:Mn is 4 at.% and PVDF films contain 3 wt.% ZnS:Mn particles, the PVDF/ZnS:Mn flexible thin-film sensors demonstrate excellent mechano-luminescence performance.

Study of Optical, Thermal, Mechanical and Microstructural Properties of Fullerene/Poly (vinylidene fluoride) Polymer Nanocomposites

Fullerene (C60)/ poly (vinylidene fluoride) PVDF polymer nanocomposites (PNCs) films were prepared using a solution casting route. The optical, microstructural, thermal, and mechanical properties of pure PVDF and C60-PVDF polymer nanocomposite films were studied using UV-Visible & Fourier Transform infrared (FTIR) spectrophotometer, X-ray diffractometer, Thermo-gravimetric analyzer, Tensile tester, and Field emission scanning electron microscope. An absorption band near 350 nm in the absorption spectrum shows the presence of C60 nanoparticles in the PNC film. In the FTIR spectrum, the presence of vibrational bands near 510 and 840 cm-1 suggest the development of β-phase of PVDF in PNC films. An increase in the degradation temperature from 444 0C in pure PVDF to 506 0C in PNC with 0.5 wt% C60 is ascribed to cross-linking occurring between C60 and polymer in PNC films. Both thermal conductivity and Young’s modulus vary non-linearly with C60 content in PNC films. Microscopic image shows agglomerated C60 particles of diameter ~550 nm, which were cross-linked to PVDF particles.

Mechanically and electrically robust, electro-spun PVDF/PMMA blend films for durable triboelectric nanogenerators

Electrospinning is an efficient and promising technique to prepare flexible, lightweight, electrical polarized nanofibrous for wearable triboelectric nanogenerators (TENGs). However, the electro-spun films fail easily during the friction process due to the poor mechanical property. Herein, mechanically and electrically robust poly (vinylidene fluoride)/ poly (methyl methacrylate) (PVDF/PMMA) blend film were prepared by electrospinning methods. Owing to the hydrogen bonding formation by PMMA incorporation, the tensile strength of electro-spun PVDF/PMMA blend films achieve 4-fold enhancement compared with pure PVDF films. The optimized TENG based on the blend films exhibits a superior open-circuit voltage of 810 V, short-circuit current of 70 μA and maximum peak power density of 13.8 W/m2. Excellent outputs stability of the device with negligible fluctuations over 10,000 cycles is demonstrated. This work provides an effective approach of simultaneously optimizing the electrical property and mechanical property of triboelectric materials, further broadening the application of TENGs in daily life.