PVDF Composites Research Articles

Submicron graphite platelet-incorporated PVDF composite: an efficient body motion-based energy harvester for flexible electronics

Submicron graphite platelet-incorporated PVDF composite: an efficient body motion-based energy harvester for flexible electronics

A Study on the Underwater Energy Harvester with Two PVDFs Installed on the FTEH and CTEH at the End of the Support.

In this study, two thin rectangular PVDFs were installed in the form of a cantilever on a FTEH (funnel-type energy harvester), and a CTEH (cymbal-type energy harvester) was fabricated in a form coupled to the upper part of the support. As a result of measuring the energy harvesting sensitivity according to the installation direction of the CTEH, a high voltage was measured in the structure installed on top of the support across all flow velocity conditions. A composite structure PVDF energy harvester combining CTEH and FTEH was fabricated and the amount of power generated was measured. As a result of measuring the open-circuit voltage of the PVDF energy harvester device with a composite structure to which the optimum resistance of CTEH of 241 kΩ and the optimum resistance of FTEH of 1474 kΩ were applied at a flow rate of 0.25 m/s, the output voltage compared to the RMS average value was 7 to 8.5 times higher for FTEH than for CTEH. When the flow rate was 0.5 m/s, the electrical energy charged for 500 s was measured as 2.0 μWs to 2.5 μWs, and when the flow speed was 0.75 m/s, it reached 2.5 μWs when charged for 300 s, generating the same amount when the flow rate increased by 50%. The time to do it was reduced by 66.7%.

Significantly Suppressed Dielectric Loss and Enhanced Breakdown Strength in Core@Shell Structured Ni@TiO2/PVDF Composites

An insulating shell on the surface of conductive particles is vital for restraining the dielectric loss and leakage current of polymer composites. So as to inhibit the enormous loss and conductivity of pristine nickel (Ni)/poly(vinylidene fluoride)(PVDF) composites but still harvest a high dielectric permittivity (εr) when filler loading approaches or exceeds the percolation threshold (fc), pristine Ni particles were covered by a layer of titanium dioxide (TiO2) shell via a sol-gel approach, and then they were composited with PVDF. The impacts of the TiO2 coating on the dielectric performances of the Ni/PVDF composites were explored as a function of the filler concentration, the shell thickness and frequency. In addition, the dielectric performances were fitted using the Havriliak-Negami (H-N) equation in order to further understand the TiO2 shell's effect on polarization mechanism in the composites. The Ni@TiO2/PVDF composites exhibit high εr and enhanced breakdown strength (Eb) but remarkably suppressed loss and conductivity when compared with pristine Ni/PVDF because the TiO2 shell can efficiently stop the direct contact between Ni particles thereby suppressing the long-range electron transportation. Further, the dielectric performances can be effectively tuned through finely adjusting the TiO2 shell' thickness. The resulting Ni@TiO2/PVDF composites with high εr and Eb but low loss show appealing applications in microelectronics and electrical fields.

Synergistic enhancement in mechanical, thermal, and dielectric properties of PANI@BT/PVDF composites by adding 2D nanoplatelets

AbstractPolymer‐based dielectric composites with simultaneously improved dielectric constant and breakdown strength have great potential applications in energy storage. In this paper, polyaniline@BaTiO3 (PANI@BT) nanoparticles with core‐shell structure are first fabricated by in‐situ chemical oxidative polymerization, and deposited on the surface of two‐dimensional nanoplatelets (graphene oxide [GO] and hexagonal boron nitride nanosheets [BNNS]), which are then utilized to prepare poly(vinylidene fluoride) (PVDF)‐based composites. The presence of 2D nanoplatelets is found to significantly ameliorate the dispersion of PANI@BT particles in the PVDF matrix, and thus endowing the resultant PVDF composites with improved comprehensive performance. The dielectric constant of PANI@BT‐GO/PVDF and PANI@BT‐BNNS/PVDF composites with 50 wt% fillers increase to 124.9 and 169.5 at 100 Hz, accompanied with relatively low dielectric loss. When the filler content is 10 wt%, the breakdown strength of PANI@BT‐BNNS/PVDF achieves 133.5 kV/mm, which is 9.7% and 71.8% higher than that of the pristine PVDF and PANI@BT/PVDF composites. Meanwhile, the tensile stress also reaches the highest value of 43.38 MPa. In addition, the PANI@BT‐GO/PVDF and PANI@BT‐BNNS/PVDF composites present higher thermal decomposition temperature in comparison with PANI@BT/PVDF composites.

Electrical field stimulated modulation of cell fate of pre-osteoblasts on PVDF/BT/MWCNT based electroactive biomaterials.

The present study reports the impact of the interplay between electroactive properties of the biomaterials and electrical stimulation (ES) toward the cell proliferation, migration and maturation of osteoprogenitors (preosteoblasts; MC3T3-E1) on the electroactive poly (vinylidene difluoride) (PVDF)-based composites. The barium titanate (BaTiO3; BT; 30 wt%) and multiwalled carbon nanotubes (MWCNT; 3wt%) were introduced into the PVDF via melt mixing, which led to an enhancement of the dielectric permittivity, electrical conductivity, and surface roughness. We also present the design and development of an in-house customized 12-well plate-based device for providing different types (DC, square, biphasic) of ES to cells in culture in a programmable manner. In the presence of ES of 1V cm-1 , biophysical stimulation experiments performed using 12-well plate-based device revealed that PVDF composite (PVDF/30BT/3MWCNT) can facilitate the enhanced adhesion and proliferation of the MC3T3-E1 in non-osteogenic media, with respect to non-stimulated conditions. Importantly, MC3T3-E1 cells demonstrated significantly better migration and differentiation on the PVDF/30BT/3MWCNT under ES when compared to ES-free culture conditions. Similar enhancement with respect to alkaline phosphatase activity, intracellular Ca2+ concentration, and calcium deposition in MC3T3-E1 cells was recorded, when pre-osteoblasts were grown for 21 days on electroactive substrates. All these observations supported the activation of osteo-differentiation fates, which were further promoted in the osteogenic medium. The present study demonstrates that the synergistic interactions of ES with piezoelectric PVDF-based polymer composite can potentially enhance the proliferation, migration, and osteogenesis of the pre-osteoblast cells, rendering it a promising bioengineering strategy for bone tissue engineering.

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.

Poly (vinylidene fluoride)-based microcellular dielectrics filled with polydopamine coated carbon nanotubes for achieving high permittivity and ultralow dielectric loss

Poly (vinylidene fluoride) (PVDF)-based microcellular dielectrics with polydopamine (PDA) coated carbon nanotubes (CNTs) were fabricated through scCO2 foaming technologies. Compared with pristine CNT/PVDF foam composites, the dielectric permittivity and loss factor of coated composites were much lower due to the significantly reduced polarizability within particle/polymer interfaces. Besides, these two parameters were also reduced with increasing expansion ratio, which was ascribed to the disaggregation of conductive particles and the increased air in the cells. Furthermore, it was demonstrated that more nucleation points initiated by the enlarged saturation pressure yielded the increased number of cells and the space restriction led to a mild growth of the cell size, which benefited for minimizing the increase of inter-particle spacing and the disentanglement between particles. Accordingly, the PDA@CNT/PVDF composites foamed to a high ER achieved a relatively large permittivity and an ultralow dielectric loss, which paved a new way to fabricate microcellular dielectrics.

Analysis of electrospinning and additive effect on β phase content of electrospun PVDF nanofiber mats for piezoelectric energy harvester nanogenerators

Harvesting energy with piezoelectric nanoparticles enables the development of self-powered devices. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF) has been widely used in a variety of fields due to its superior piezoelectric properties. PVDF’s piezoelectric performance is affected by the presence of polar phase in the crystalline structure. The electrospinning process was used in this study to achieve high β phase ratios in the PVDF crystalline structure using various additives (graphene, boron nitride, and quartz (SiO2)). The Taguchi experimental design method was used to determine the most significant parameters affecting β phase content from seven factors, as well as the optimal levels of the significant factors. The Fourier transform infrared, x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray and differential scanning calorimetry analyses were used to characterize the composite PVDF nanofiber mats produced under optimal conditions, and the output voltage was measured using an oscilloscope. The composite PVDF nanofiber mat with the highest β phase concentration demonstrated a maximum output voltage of 8.68 V under optimal conditions, indicating that it outperformed than pure PVDF under equal electrospinning conditions.

Pollution Removal Performance of Chemically Functionalized Textile Waste Biochar Anchored Poly(vinylidene fluoride) Adsorbent

Preparation of adsorbent materials in powder and polymeric composite form was achieved by controlled carbonization of ZnCl2 pretreated textile waste at low temperatures. Structural and surface properties of carbonized textile waste samples (CTW) and polymeric composites were prepared by the addition of CTW to PVDF-DMF solution at 0, 5, 10, 15, 20, and 30 mass% ratios analyzed by FT-IR, XRD, SEM, and BET analysis. Adsorption performances of powder and composite adsorbents were investigated for MO dye removal from an aqueous solution. Zn-CTW obtained with carbonization of ZnCl2 treated textile waste at 350 °C presented 117.5 mg/g MO removal. Those were higher than CTW-350 and CTW-400. The presence of 1545 cm-1 band at the IR spectrum of Zn-CTW proved the formation of functional groups that increase dye adsorption performance with honeycomb-like pores on the surface. Zn-CTW reflected its properties onto the PVDF matrix. Improved porosity percentage, BET surface, and dye adsorption of Pz20 were recorded as 105.3, 15.22 m2/g, and 41 mg/g, respectively, compared with bare PVDF. Disposal of textile waste and preparation of functional activated carbon were achieved in a low-cost and easy way. Zn-CTW loaded PVDF composites are promising materials to use as a dye removal adsorbent from water or filtration membranes.

Tunable BaxSr1-xTiO3 nanoparticles induced high energy storage density in layer-structured asymmetric polymer-based nanocomposites

In order to solve the problem of low charging and discharging energy density of dielectric capacitors, the structure design of layered polymer matrix composites is carried out in this paper. Ba0.7Sr0.3TiO3, Ba0.8Sr0.2TiO3 and Ba0.9Sr0.1TiO3 nanoparticles were successfully prepared by the oxalate coprecipitation method. The surface of BaxSr1-xTiO3 was successfully coated with dopamine, which promoted the dispersion of the polymer matrix of the ceramic powder. Monolayer BaxSr1-xTiO3/PVDF composites containing BaxSr1-xTiO3 with different Ba/Sr ratios were successfully prepared by the casting method. Three-layer asymmetric composites with different fillers were successfully prepared by layer-by-layer casting. The phase and microstructure of the as-prepared materials were analyzed by XRD and SEM. The dielectric, electrical conductivity, ferroelectric and energy storage properties of the composites were tested. The effects and laws of the design of the three-layer asymmetric structure on the dielectric properties and energy storage properties of the layered composites are mainly studied. When the structure of the three-layer asymmetric composite is 1-2-3, the breakdown field strength reaches 330 kV/mm, the discharge energy density reaches 8.51 J/cm3, and the charge-discharge efficiency is 67%. This work demonstrates that layered composites with asymmetric properties can facilitate the development of electrical energy storage.

Insights into concomitant enhancements of dielectric properties and thermal conductivity of PVDF composites filled with core@double‐shell structured Zn@ZnO@PS particles

AbstractIn order to synchronously improve dielectric permittivity (ε′), breakdown strength (Eb), and thermal conductivity (TC) while inhibiting dissipation factor (tan δ) of raw Zn (Zinc)/PVDF (poly[vinylidene fluoride]) composites, two kinds of core‐shell structured particles of Zn@ZnO (zinc oxide) and Zn@ZnO@PS (polystyrene) were synthesized by high‐temperature oxidation followed by suspension polymerization, then they were composited with PVDF to elaborately generate morphology‐controllable high‐ε′ but low loss, and high TC composites. The results confirm that both the Zn@ZnO/PVDF and Zn@ZnO@PS/PVDF composites show markedly improved ε′, suppressed tan δ and conductivity over the original Zn/PVDF because of the induced multiple polarizations in the Zn@ZnO and Zn@ZnO@PS configurations and the barrier effect of constructed shells on direct contact of Zn particles. The second organic PS shell inhibits the loss and conductivity due to its high‐electrical resistivity, and further boosts the Eb and TC of the composites owing to enhanced interfacial compatibility between the Zn@ZnO and PVDF, which lessens the local electric field distortion and concentration, and therefore, promotes phonon transport across the interfaces through suppressing the thermal interfacial resistance. The prepared Zn@ZnO@PS/PVDF with a high Eb and ε′ but low tan δ, as well as enhanced TC, exhibit appealing potential applications in microelectronic devices and power equipment.

Towards synchronously improving dielectric performance and thermal conductivity in Ni/PVDF by tailoring core-shell structured Ni@NiO particles

An insulating interlayer between conductive particles and polymer is crucial for preparing polymer dielectrics with high dielectric permittivity ( ε) but low loss and high breakdown strength ( Eb). To restrain the large loss of raw nickel (Ni)/poly (vinylidene fluoride) (PVDF) composites when still maintaining a high- ε at the percolation threshold ( fc) of conductive fillers, in this work, nanoscale nickel oxide (NiO) shell with diverse thickness was coated around the surface of Ni particles via a facile thermal calcination at 650°C under air, and the gained Ni@NiO particles were composited with PVDF to produce morphology-controllable high- ε, low loss composites. The influences of the NiO shell and thickness on the dielectric performances and thermal conductivity (TC) of the composites were investigated in terms of filler loading and frequency. Compared with raw Ni/PVDF, the Ni@NiO/PVDF composites exhibit remarkably suppressed dielectric loss and enhanced Eband TC because the NiO interlayer not only prevents the Ni particles from direct contact and hinders the long-range electron migration thereby resulting in rather low leakage current, but also simultaneously suppresses thermal interfacial resistance and enhances interfacial compatibility between the fillers and the matrix subsequently resulting in improved TC. Therefore, the Ni@NiO/PVDF with high ε-low loss, heightened Eband TC present appealing potential applications in microelectronics and electrical industries.

Epsilon-near-zero response derived from collective oscillation in the metacomposites with ultralow plasma frequency

Nowadays, negative parameters have been originally brought up and investigated in the electromagnetic metamaterial, where the epsilon-near-zero (ENZ) response was dominated by collective plasma frequencies and carrier concentration. However, the ENZ response is missing at the radio frequency, leading to limitations on novel antennas and printed circuit board. Therefore, ternary copper/silica coated copper/polyvinylidene fluoride (Cu/Cu@SiO2/PVDF) composites were prepared to investigate the ENZ response at the radio frequency. With increasing the content of Cu granules, a transition from positive to negative permittivity was observed in the binary Cu/PVDF composites, in which negative permittivity was related to an inductive character. On the contrary, the binary Cu@SiO2/PVDF composites without any uncoated Cu granules exhibit positive permittivity, showing a capacitive character. In fact, negative permittivity was derived from the collective plasma oscillation of percolative Cu networks, and Cu@SiO2 granules were responsible for diluting effective electron concentration of Cu. For the ternary Cu/Cu@SiO2/PVDF composites, values of negative permittivity were suppressed to several orders of magnitude to −178 (measured at 1 MHz) and plasma frequency decreased to radio frequency about 106 rad/s. Besides, with the construction of percolative Cu networks, the Ac conduction mechanism was transformed from hopping conduction to metal-like conduction. Based on the equivalent circuit analysis, it showed that a permittivity transition was responsible for the capacitive to inductive character.

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.

Nanoparticle-Enhanced β-Phase Formation in Electroactive PVDF Composites: A Review of Systems for Applications in Energy Harvesting, EMI Shielding, and Membrane Technology

Nanoparticle-Enhanced β-Phase Formation in Electroactive PVDF Composites: A Review of Systems for Applications in Energy Harvesting, EMI Shielding, and Membrane Technology

Evaluation of piezoelectric behavior and biocompatibility of poly(vinylidene fluoride) ultrafine fibers with incorporated talc nanosheets

AbstractHerein, we fabricated biocompatible ultrafine fibers based on talc nanosheets (TNS)/PVDF composites that can exhibit robust electromechanical responses. Piezoresponse force microscopy (PFM) was extensively used to decode various characteristics, including ferroelectric and piezoelectric coefficients. The 0.5 wt% TNS dispersed ultrafine fibers exhibited well‐defined ferroelectric characteristics with an enhanced piezoelectric coefficient (d33) of ≈43.3 pm/V compared to 10 pm/V measured for the pristine PVDF ultrafine fibers. It was observed that the piezoelectric coefficient values strongly depended on the morphology and electroactive phase fraction of the ensuing composite ultrafine fiber. The advantage of a high aspect ratio and surface charges offered by TNS alongside electrospinning augmented the composite ultrafine fiber's piezoelectric response. Further, in‐vitro cytotoxicity of the TNS/PVDF composite ultrafine fibers was examined using BALB/3T3 fibroblasts based on ISO Standard 10993‐5. Importantly, the new composite fibers showed no cytotoxic response and the exposed fibroblasts showed excellent viability. Thus, these fabricated TNS/PVDF piezoelectric ultrafine fibers are well suited for applications in bioelectronics, especially as flexible wearable electronic devices, including sensors.

Core@double-shell structured fillers for increasing dielectric constant and suppressing dielectric loss of PVDF-based composite films

High dielectric constant polymer dielectrics have attracted a great deal of attention in flexible electronics. However, it appears to be a paradox for polymer dielectrics that the enhancement of their dielectric constant often comes along with the increase of dielectric loss. Hence, we reported core@double shell structured filler/poly(vinylidene fluoride) (PVDF) composites to overcome this paradox. The hybrid filler with BaTiO3 (BT) as the core, conductive carbon as the inner shell, and insulating polydopamine (PDA) as the outer shell was synthesized. As a result, the BT@C@PDA/PVDF composites at the filler content of 11 vol% exhibit an outstanding dielectric performance with a dielectric constant of 45 and a dielectric loss of 0.053 at 103 Hz. This phenomenon can be attributed to the increased interfacial polarization induced by the inner carbon shell and the conductive paths blockade caused by the outside PDA shell inside the BT@C@PDA/PVDF composites. This work reveals that rational design of core@double shell structured hybrid fillers maybe a promising way to optimize the overall dielectric performance of the PVDF-based composites.

Lead-free, high-current output piezoelectric nanogenerators using three-dimensional interdigitated electrodes

Harvesting mechanical energy based on piezoelectricity has attracted extensive attention, but achieving lead-free piezoelectric nanogenerators (PENGs) with high output current is still a big challenge, which severely limit their wide applications. Here, to address it, flexible composites with excellent piezoelectric capability are proposed and used to fabricate lead-free, high-current output PENGs using three-dimensional (3-D) interdigitated electrodes. By forming heterojunctions of Ag/(Ba,Ca)(Zr,Ti)O3 (Ag/BCZT), polarization charges in BCZT nanowires unidirectionally transfer to Ag nanoparticles under external force, resulting in the enhanced piezoelectric outputs of Ag/BCZT nanowires embedded PVDF composites macroscopically. By creating multi-layered PENGs using 3-D interdigitated electrodes (IPNGs), the total amount of polarization charges increased, giving rise to the significantly improved output current. Optimally, the 4-unit IPNG can generate a proper voltage of 20 V and a considerable current of 15 μA (corresponding current density is 3.75 μA/cm2), which is higher than the other lead-free piezoceramics based PENGs previously. The excellent outputs can also charge a 1 μF capacitor from 0 V to 5.3 V in 30 s (equivalent charge density is 272 μC/m2). This work presents a brand-new paradigm for high-performance PENGs from the perspective of material and device design.

Enhanced dielectric and thermal properties of Zn/PVDF composites by tailoring core@double-shell structured Zn particles

In this study, poly(vinylidene fluoride) (PVDF) composites containing a core@double-shell structured zinc (Zn) filler (i.e., Zn@ZnCH@ZnO) were synthesized. The primary focus is to investigate the effect of double shell on the polarization mechanism of composites by analyzing the dielectric properties and fitting the experimental data with a Havriliak–Negami (HN) expression. The results verify that the Zn@ZnCH@ZnO/PVDF composites exhibit prominently enhanced dielectric constant, suppressed loss and conductivity over pure PVDF and the pristine Zn/PVDF thanks to induced multiple polarizations generated in the core@double-shell configuration. The fitting curves reveal that the multiple polarizations are derived from the combined contributions of the α relaxation of PVDF, fast intra-particle polarization and slow inter-particle polarization. Furthermore, the thermal conductivity of Zn@ZnCH@ZnO/PVDF composites is enhanced by changing the amorphous ZnCH to crystalline ZnO shell promoting phonon transport. This work opens a new avenue to obtain comprehensively good performances of dielectric composites for potential application in microelectronics.

Novel polymer composites of RuO2@nBaTiO3/PVDF with a high dielectric constant

The dielectric properties of a novel polymer dielectric material were investigated. The conductive phase of RuO2 was synthesized for deposition on the surface of a nanosized BaTiO3 (nBT). The RuO2@nBT hybrid particles were incorporated into a poly (vinylidene fluoride) (PVDF) as a three-phase composite (RuO2@nBT/PVDF). The obtained dielectric constant (ε′) was significantly high (3837.16) for the composite with a volume fraction of fRuO2@nBT = 0.50. The large interfacial polarization between the RuO2−nBT and RuO2−PVDF interfaces considerably increased the value of ε′. Therefore, interfacial polarization is a critical factor in improving the dielectric properties. The dielectric behavior of the RuO2@nBT/PVDF composites can be described using the effective medium percolation theory model, which indicates the significant contributions of the conductive RuO2 phase and high-permittivity nBT phase.