Polyvinylidene Fluoride Fibers Research Articles

Fabricating high-performance biomedical PLLA/PVDF blend micro bone screws through in situ structuring of oriented PVDF submicron fibers in microinjection molding

Poly(l-lactide) (PLLA) is regarded as a polymer with excellent biocompatibility, but its inherent brittleness property greatly restricts its application in the biomedical engineering field. Blending PLLA with other polymers is one of the sufficiently viable methods of property improvement. In this paper, the Poly(l-lactide) (PLLA)/Polyvinylidene fluoride (PVDF) blend was first prepared by melt-compounding, and then microinjection molded into the blend micro bone screw with high strength and toughness. The experimental results show that the PVDF dispersed phases could in situ form the highly oriented fibers with shish-kebab structures under the effect of strong shear stress field of microinjection molding along flow direction. These parallelly aligning PVDF fibers could simultaneously realize the significant enhancement in both toughness and strength of the micro bone screw. Specifically, in the bending test the blend micro bone screw with oriented PVDF fibers can withstand the compression displacement of nearly 2 mm, while the neat PLLA one would break within only 0.5 mm displacement. In addition, a bending recovery phenomenon was observed in the load-displacement curve of the blend, demonstrating the mechanical transition from brittle fracture to ductile fracture. Moreover, with addition of 30 % PVDF, the elongation at break increases from 7.8 % to 57.8 %, while the tensile strength increases from 60.9 MPa to 74.3 MPa. The PLLA/PVDF micro screws possess better toughness and excellent biocompatibility compared to pure PLLA products. They also exhibit great potential for stimulating the proliferation of cells through piezoelectric output, opening up new possibilities for the development of next-generation fracture fixation materials.

A novel centrifugal electrospinning design for preparing of high alignment β-phase PVDF nanofibers for high-performance piezoelectric nanogenerators

The effects of polyvinylidene fluoride (PVDF) wt. % and electric fields on the production of PVDF fibers using a novel centrifugal electrospinning design were investigated. High-quality, bead-free fibers with diameter of (0.55 ± 0.04) μm were successfully produced. Fibers with exceptionally high β-phase content of 96.1 % and piezoelectric coefficient, d33 of (−157 ± 5) pC N−1 were obtained using PVDF amount and electric field of 14.0 wt % and 400 V cm−1, respectively. Under 3.0 N repetitive vertical forces, the fabricated piezoelectric nanogenerator (PENG) exhibited impressive open-circuit voltage, short-circuit current and power density of (32.6 ± 0.7) V, (3.26 ± 0.07) μA and (15.4 ± 0.6) μW cm⁻2, respectively. The production of high and well aligned β-phase in the fibers indicated by good d33 values are the likely reasons for the excellent performance of the PENG. Ultimately, potential of the fabricated PENG as a self-power supply for low-energy electronic devices was demonstrated.

Hollow anion-Janus-modified poly(vinylidene fluoride) (PVDF) fiber membranes for nanosized virus removal

In this study, a hollow polyvinylidene fluoride (PVDF) fiber was developed and modified into a Janus membrane (Janus-VM) and an entirely hydrophobic membrane (Hydrophobic-VM) for removing 20-nm-scale viruses during biopharmaceutical processing. The Janus-VM has anionic properties on the outer and feed hydrophilic surfaces, and the inner pore surface (I.P.S) maintains the anionic-hydrophobic properties of the PVDF. Theoretically, an electrostatic repulsion force might be formed between the surface of the strong anionic membrane and anionic bacteriophages, preventing bacteriophages from adsorbing to the membrane surface. As a result, water flux can be increased through the reduction of membrane fouling. The PVDF membrane was modified through UV-irradiation, which causes –OH radicals to form on the membrane surface, and chemical grafting with anionic-hydrophobic/anionic-hydrophilic modifiers, which enhances the membrane’s anion characteristics (−27, −48 mV). Additionally, the average pore size was reduced from 34 nm to less than 20 nm through chemical surface modification, after which the Janus membrane showed an excellent initial water flux, with the protein recovery ratio (PRR) approaching 98.9 %. UV absorbance analysis revealed 100 % removal efficiency for 20- and 40-nm gold particles on the membranes. Furthermore, the initial log reduction value (LRV) was observed through flux performance using MS2 and PP7 bacterial phages, for which the Janus membrane showed an excellent virus removal performance (LRV > 6.8 and 6.5).

Textured CsPbI3 nanorods composite fibers for stable high output piezoelectric energy harvester

The utilization of piezoelectric nanogenerator (PENG) based on halide perovskite materials has demonstrated significant promise for energy harvesting applications. However, the challenge of synthesizing halide perovskite materials with both high output performance and stability using a straightforward process persists as a substantial obstacle. Herein, we present the fabrication of CsPbI3 nanorods (NRs) exhibiting highly uniform orientation within polyvinylidene fluoride (PVDF) fibers through a simple texture engineering approach, marking the instance of enhancing PENG performance in this manner. The resultant composite fibers showcase a short-circuit current density (Isc) of 0.78 μA·cm−2 and an open-circuit voltage (Voc) of 81 V, representing a 2.5 fold increase compared to the previously reported highest value achieved without the electric poling process. This outstanding output performance is ascribed to the orientation of CsPbI3 NRs facilitated by texture engineering and dipole poling via the self-polarization effect. Additionally, the PENG exhibits exceptional thermal and water stability, rendering it suitable for deployment in diverse and challenging environmental conditions. Our findings underscore the significant potential of textured CsPbI3 NRs composite fibers for powering low-power consumer electronics, including commercial LEDs and electronic watches.

Bioinspired construction of petal-like regenerated PVDF/cellulose fibers for efficient fog harvesting

Water collection from atmospheric fog was deemed to be an efficient and sustainable strategy to defuse the freshwater scarcity crisis. Fog harvesting and trapping fibers, therefore, has aroused extensive interest due to their ease of preparation, weave, and use. However, the traditional fibers used in fog collector usually have a low fog collection capacity and efficiency because of their unreasonable morphology and structure design. Herein, we proposed a simple process to construct advanced fibers using a one-step wet spinning of hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic cellulose mixture fiber for fog harvesting. The as-prepared fibers featured a petaloid structure and surface hydrophobic gradient, thus facilitating fog deposition, water droplet formation, and drainage. The unique longitudinal groove structure above enabled the hybrid fiber to achieve an excellent fog collection efficiency of 2750.26 mg/cm2/h per monofilament, which outstripped most of other fiber materials. When woven these fibers were in a longitudinal array network with an interval of 1 mm, and the fog collection efficiency can maintain at 10.30 L/m2/h. Therefore, this work provided a new strategy for further exploration of effective fog collection by cellulose-based fiber materials.

A self-powered piezoelectric Poly(vinyl alcohol)/Polyvinylidene fluoride fiber membrane with alternating multilayer porous structure for energy harvesting and wearable sensors

Development of flexible wearable electronic devices requires high-performance piezoelectric sensors, being advantageous in high sensitivity, ease to microintegration without external power supply. In this work, poly(vinyl alcohol) (PVA)/polyvinylidene fluoride (PVDF) fiber membranes with stable alternating multilayer structure were constructed through electrospinning and subsequent gas-phase crosslinking. The PVA/PVDF fiber was fully stretched with smooth surface and uniform diameter at appropriate PVDF concentration, exhibiting high porosity (88 %). The α-phase was transformed into the electroactive β-phase of PVDF in the electrospinning process, while the crystallinity and β-phase percentage (Fβ) were improved by mixing spinning of PVA and PVDF, with Fβ reaching above 90 %. The PVA/PVDF fiber membrane showed high mechanical strength/toughness and liquid absorbency (719.03 %). The significant electrical signal output (10.07 V and 166.42 nA) was generated, accompanying with high stress sensitivity, short response time and high stability, exhibiting excellent piezoelectricity and making the fiber membrane not only monitor large deformation movements of limbs as self-powered wearable sensor, but also sense weak signals of pulse, breathing etc. for monitoring human health, as well as environmental humidity. Meanwhile, the harvested energy could drive electronic device, showing prosperous potentials in fields of artificial intelligence.

Flexible Magnetocaloric Fiber Mats for Room-Temperature Energy Applications.

Currently, magnetocaloric refrigeration technologies are emerging as ecofriendly and more energy-efficient alternatives to conventional expansion-compression systems. However, major challenges remain. A particular concern is the mechanical properties of magnetocaloric materials, namely, their fatigue under cycling and difficulty in processing and shaping. Nevertheless, in the past few years, using multistimuli thermodynamic cycles with multicaloric refrigerants has led to higher heat-pumping efficiencies. To address simultaneously the challenges and develop a multicaloric material, in this work, we have prepared magnetocaloric-based flexible composite mats composed of micrometric electroactive (EA) polyvinylidene fluoride (PVDF) fibers with embedded magnetocaloric/strictive La(Fe,Si)13 particles by the simple and cost-effective electrospinning technique. The composite's structural characterization, using X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and measurements of the local-scale piezoresponse, revealed a cubic NaZn13-type structure of the La(Fe,Si)13 phase and the formation of the dominant polar β-phase of the PVDF polymer. The PVDF-La(Fe,Si)13 composite showed an enhancement of the longitudinal piezoelectric coefficient (effective d33) (-11.01 pm/V) compared with the single PVDF fiber matrix (-9.36 pm/V). The main magnetic properties of La(Fe,Si)13 powder were retained in the PVDF-La(Fe,Si)13 composite, including its giant magnetocaloric effect. By retaining the unique magnetic properties of La(Fe,Si)13 embedded in the electroactive piezoelectric polymer fiber mats, we have designed a flexible, easily shapeable, and multifunctional composite enabling its potential application in multicaloric heat-pumping devices and other sensing and actuating devices.

Interaction of material- and structural elasticity – an approach towards a physiological compliance in small-caliber vascular grafts

Research purpose: The low patency rate (less than 50% at a 5-years follow-up) of commercial vascular grafts is strongly associated with compliance mismatch between graft und native artery. To address this deficit, we investigated the influence of the material and structural elasticity on the compliance behavior of small caliber vascular graft gaining for a stress-strain behavior adapted to the native vessel. Material & Methods: By combining different thermoplastic polycarbonate urethanes (TPU) fibers with different elasticity and non-elastic polyvinylidene fluoride (PVDF) fibers in different warp knitted tubular textile structures, we incorporate material and structural elasticity in a vascular graft (I.D. < 6 mm). The evaluation of the tubular fabrics is performed by determining the compliance properties in a mean pressure range between 20 and 120 mmHg by tensile testing. Results: We identified the draw ration of the TPU fiber production, the stitch course density of the fabric and the thread tension of the TPU yarn during the warp knitting process as statistically highly significant effects ( p < .005) on the compliance. With an adapted setting of those parameters, we were able to improve the compliance of the textile vascular grafts over the entire physiological pressure range (20–120 mmHg) by 400–630 % compared to current clinical ePTFE (expanded polytetrafluoroethylene) grafts towards native vessels. Conclusion: By combining material and structural elasticity in a warp knitted textile structure, we were able to biomimic the compliance towards physiological properties. Our approach can be seen as blueprint to adapt elasticity properties in other implant applications.

3D network of zinc powder woven into fibre filaments for dendrite-free zinc battery anodes

Zinc foil metal anodes in aqueous zinc ion batteries (AZIBs) are impaired by uncontrollable dendrite growth, resulting in low Coulombic efficiency (CE) and limited lifetime. The tunability of zinc powder provides a perfect alternative for anodes. But their rough spherical surfaces possibly make them more susceptible to corrosion and dendrite growth. We hereby utilise electrostatic spinning to weave zinc powder into polyacrylonitrile/ Polyvinylidene fluoride (PVDF/PAN) fiber filament to produce a new three-dimensional porous zinc anode (PF@Zn). Stable and flexible structure of the constructed fiber filament framework avoids direct contact of the aqueous electrolyte with the collector while relieving the stresses generated by dendrite growth. Moreover, when galvanizing or stripping, the zinc powder woven into the fiber network efficiently homogenizes the Zn2+ ion flux for a stable zinc cycle. Accordingly, the PF@Zn anode battery has a superior cycle life (240 h) and an increased Coulombic efficiency (99.1 %). An assembled C//PF@Zn capacitor has an impressive 96.6 % capacity retention after 3000 cycles. The study offers a scalable approach to modifying metal powder electrodes and transforming them into high-performance batteries.

PVDF composite fibers for wireless fall-alert detection

As the demand for healthcare devices continues to rise, novel technologies centered on personalized motion monitoring systems are being developed, wherein wearable sensors play a pivotal role. In the present investigation, an innovative wireless apparatus for detecting falls is introduced, which encompasses a specifically engineered pressure sensor composed of polyvinylidene fluoride (PVDF) composite fibers. Our design consists of high β-phase content of electrospun composites including 0.1 wt% of zinc oxide/reduced graphene oxide (ZnO/rGO) hybrid (mass ratio 90/10) which shows enhanced electrical voltage of 11.36 ± 0.72 V compared to pristine PVDF fiber. This piezoelectric pressure sensor is integrated with a wireless embedded system capable of transmitting an “SOS” message to a mobile phone upon the user’s fall experience. Such wearable fall alert detection systems with improved characteristics could benefit the elderly and patients requiring continuous monitoring for possible falls.

Development of multi-directional piezoelectric sensor doped with graphene by near-field electrospinning technology for calligraphy writing

A novel multi-directional (MD) circular-shaped fiber piezoelectric sensor was developed to detect calligraphy writing force from various directions quantitatively. The sensor was fabricated using polyvinylidene fluoride (PVDF) piezoelectric fibers doped with Graphene and spun using direct-write near-field electrospinning (NFES) technology. The NFES collector, designed as a rotating disc system, orderly collected the fibers to enhance the piezoelectric effect and dipole moments, forming the circular sensor. Flexible electrical electrodes with multiple signal output circuits were incorporated for calligraphy stroke sensing, bonded with circular PVDF fibers to create the flexible MD sensor. With inner and outer diameters of 20[Formula: see text]mm and 60[Formula: see text]mm, the circular sensor responded to deformable signals induced by calligraphy strokes. Parameters of sensor fabrication were optimized using the uniform design experimental method. Calibration involved tapping tests at 1–10[Formula: see text]Hz to correlate fiber output voltage with the corresponding force. The single sensor reached a maximum voltage output of approximately 908[Formula: see text]mV and detected forces ranging from 0.1 to 50[Formula: see text]N. After validating the MD circular-shaped piezoelectric sensor, a [Formula: see text] sensor array was configured for calligraphy writing force sensing, providing quantitative measurements of dynamic responses during writing, valuable as a data source for apprentice learning.

Highly durable platinum group metal-free catalyst fiber cathode MEAs for proton exchange membrane fuel cells

Fe-based platinum group metal (PGM)-free catalysts were incorporated into electrospun fiber mat or powder cathode membrane-electrode-assemblies (MEAs) with a Nafion 211 membrane and a Pt/C powder anode. Fabrication and characterization tests were performed on MEAs with: (1) a conventional powder cathode with a neat Nafion binder, (2) a fiber mat cathode with a Nafion/polyethylene oxide (PEO) binder, where PEO was extracted before MEA testing, (3) a powder cathode with a blended binder of Nafion and polyvinylidene fluoride (PVDF), and (4) a series of fiber mat cathodes with different Nafion/PVDF binder weight ratios. Cathode degradation occurred, with a loss in power output, in MEAs with a neat Nafion powder cathode or with a Nafion fiber cathode. In contrast, little or no power loss was observed for powder or fiber cathodes when the binder was a blend of Nafion and PVDF. The presence of hydrophobic PVDF drove water and electrogenerated peroxide out of the cathode, away from catalyst particles, which improved cathode durability, but PVDF also decreased the binder conductivity and slowed oxygen reduction kinetics, resulting in lower power densities. A 75:25 w:w Nafion:PVDF fiber cathode MEA was the best compromise for maximizing power and minimizing catalyst degradation. For such a cathode, with a PGM-free cathode catalyst loading of 3.0 mg cm−2, a power density of 88 mW cm−2 at 0.5 V, 80 °C, and 200 kPaabs pressure was maintained for 80 h of continuous operation.

Electrospun PVDF/Barium hexaferrite fiber composites for enhanced electromagnetic shielding in the X-band range

In the contemporary, digitally–driven era, the prevalence of electronic devices has drastically escalated electromagnetic (EM) pollution levels, marking a significant environmental challenge. Electrospun fiber composites of polyvinylidene fluoride (PVDF) and Barium hexaferrite (BHF) were analyzed for their potential usage in X-band electromagnetic shielding applications (EMSAs). Pure PVDF and BHF-PVDF fiber composite were manufactured by needleless electrospinning. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and EM measurements utilizing a vector network analyzer (VNA) are all used to describe the prepared samples. The XRD and FTIR analyses confirmed the successful incorporation of BHF into the PVDF matrix. The results show that adding PVDF to BHF in fiber form enhances the reflection loss (RL), indicating improved electromagnetic shielding effectiveness (EMSE). The SEM analysis revealed that the fiber composite had a uniform fiber diameter distribution. In contrast, the TGA analysis demonstrated good thermal stability of the fiber composite. Polymer samples were evaluated to enhance gamma radiation and neutron particle attenuation. MCNP5 and Phy-X/PSD software were used to study semi-crystalline fluorocarbon polymer (PVDF) and barium hex ferrite BaFe12O19 (30 wt%) with PVDF (70 wt%). The MCNP5 programme simulated 0.015–15 MeV radiation attenuation. Additionally, the Phy-X/PSD programme verified the simulated µ values for the chosen Mxenes materials. The MCNP-5 code and Phy-X/PSD results were agreed. The linear attenuation coefficients for the polymer samples ranged from 3.166 to 0.032 cm2.g−1 for PVDF and from 73.960 to 0.113 cm2.g−1 for PVDF and BHF-PVDF Fiber at photon energies from 0.015 to 15 MeV. Overall, the electrospun fiber composite of PVDF and BHF particles shows promise for EMSAs in the X-band range. The enhanced RL observed in our study suggests that these fiber composites could be used to protect against electromagnetic radiation (EMR) from electronic devices, which is increasingly concerning in today's modern society.

Optimizing Piezoelectric Coefficient in PVDF Fibers: Key Strategies for Energy Harvesting and Smart Textiles

AbstractWith the advancement in smart electronic devices and self‐powered devices, the demand for piezoelectric polymers has found potential research interest. Among these, electrospun polyvinylidene fluoride (PVDF) fibers have gained attention for energy harvesting due to their flexibility and higher piezoelectric coefficient. In the current work, various methods are compared to enhance PVDF's piezoelectric properties, including different solvents (DMAc, DMF), conductive filler (rGO), and annealing as post‐treatment. The results indicate that PVDF/rGO fibers in DMAc solvent exhibit the highest β phase fraction and crystallinity. Moreover, for the first time, the piezoelectric properties of PVDF/rGO electrospun single fiber is presented using high voltage switching spectroscopy piezoelectric force microscopy (HVSS‐PFM). The highest piezoelectric coefficient (d33) is measured for PVDF/DMAc‐rGO composite fibers. Notably, PVDF/rGO in DMAc solvent significantly improves the piezoelectric coefficient, leading to a remarkable fourfold increase in power density compared to pure PVDF, making it a promising material for energy harvesting applications.

Hydrogen Bond-Induced Activation of Photocatalytic and Piezophotocatalytic Properties in Calcium Nitrate Doped Electrospun PVDF Fibers.

In this study, polyvinylidene fluoride (PVDF) fibers doped with hydrated calcium nitrate were prepared using electrospinning. The samples were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), optical spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), Raman, and photoluminescence (PL) spectroscopy. The results are complementary and confirm the presence of chemical hydrogen bonding between the polymer and the dopant. Additionally, there was a significant increase in the proportion of the electroactive polar beta phase from 72 to 86%. It was shown that hydrogen bonds acted as a transport pathway for electron capture by the conjugated salt, leading to more than a three-fold quenching of photoluminescence. Furthermore, the optical bandgap of the composite material narrowed to the range of visible light energies. For the first time, it the addition of the salt reduced the energy of the PVDF exciton by a factor of 17.3, initiating photocatalytic activity. The calcium nitrate-doped PVDF exhibited high photocatalytic activity in the degradation of methylene blue (MB) under both UV and visible light (89 and 44%, respectively). The reaction rate increased by a factor of 2.4 under UV and 3.3 under visible light during piezophotocatalysis. The catalysis experiments proved the efficiency of the membrane design and mechanisms of catalysis are suggested. This study offers insight into the nature of chemical bonds in piezopolymer composites and potential opportunities for their use.

Effectiveness of Polyvinylidene Fluoride Fibers (PVDF) in the Diffusion and Adsorption Processes of Atrazine in a Sandy Soil

Sustainable solutions are increasingly being sought in the containment and remediation of contaminated soil and groundwater, and the use of fibers is promising. In this context, polyvinylidene fluoride fibers (PVDF) have potential applications in various fields due to their mechanical and hydraulic properties, highlighting the sorption capacity due to their hydrophobic nature and large surface area. This study aimed to evaluate the sorption capacity, adsorption, and diffusion of atrazine by PVDF fibers with a concentration of 555.63 ppm in diffusion cells containing sandy soil and a composite of the fibers in blanket format at different contents (2% and 4%) relative to the dry mass of the soil. The diffusion and determination coefficients for each cell were calculated using Wolfram Mathematica software by means of a 3D model (Space × Time × cw/c0). The absorption results showed a mass gain, with and without prior drying of the fibers, of 70% and 60%, respectively, while the adapted adsorption tests showed retained amounts of atrazine of 0%, 11.4%, and 21.8%, respectively, for the samples without fiber, with 1.5 g of fiber, and with 4 g of fiber. And finally, the diffusion coefficients resulted in 6.25 × 10−13 m2/s, 6.03 × 10−13 m2/s, and 3.64 × 10−13 m2/s, respectively, for the sample without fibers, with 1.5% fiber, and with 4% fiber. This suggests that the use of PVDF fibers may be a viable solution for the containment of contaminated soil and groundwater.

Optimization of Electrical and Mechanical Properties through the Adjustment of Design Parameters in the Wet Spinning Process of Carbon Nanotube/Polyvinylidene Fluoride Fibers Using Response Surface Methodology.

The optimal process conditions for fabricating carbon nanotube (CNT)/polyvinylidene fluoride (PVDF) fibers with varying properties using a wet spinning process were experimentally determined. A dope solution was prepared using multi-walled nanotubes, PVDF, and dimethylacetamide, and appropriate materials were selected. Design parameters affecting the chemical and physical properties of CNT/PVDF fibers, such as bath concentration, bath temperature, drying temperature, and elongation, were determined using a response surface method. The wet-spinning conditions were analyzed based on the tensile strength and electrical conductivity of the fibers using an analysis of variance and interaction analysis. The optimized process conditions for fabricating CNT/PVDF fibers with different properties were derived and verified through fabrication using the determined design parameters.

Simulation Guided Coaxial Electrospinning of Polyvinylidene Fluoride Hollow Fibers with Tailored Piezoelectric Performance.

Electrospun polyvinylidene fluoride (PVDF) piezoelectric fibers have high potential applicability in mechanical energy harvesting and self-powered sensing owing to their high electromechanical coupling capabilities. Strategies for tailoring fiber morphology have been the primary focus for realizing enhanced piezoelectric output. However, the relationship between piezoelectric performance and fiber structure remains unclear. This study fabricates PVDF hollow fibers through coaxial electrospinning, whose wall thickness can be tuned by changing the internal solution concentration. Simulation analysis demonstrates an increased effective deformation of the hollow fiber as enlarging inner diameter, resulting in enhanced piezoelectric output, which is in excellent agreement with the experimental results. This study is the first to unravel the influence mechanism of morphology regulation of a PVDF hollow fiber on its piezoelectric performance from both simulation and experimental aspects. The optimal PVDF hollow fiber piezoelectric energy harvester (PEH) delivers a piezoelectric output voltage of 32.6V, ≈3 times that of the solid PVDF fiber PEH. Furthermore, the electrical output of hollow fiber PEH can be stably stored in secondary energy storage systems to power microelectronics. This study highlights an efficient approach for reconciling the simulation and tailoring the fiber PEH morphology for enhanced performances for future self-powered systems.

Electrospun Polyvinylidene Fluoride Piezoelectric Fiber Glass/Carbon Hybrid Self-Sensing Composites for Structural Health Monitoring.

In this study, a polyvinylidene fluoride (PVDF)/graphene nanoplatelet (GNP) micro-nanocomposite membrane was fabricated through electrospinning technology and was employed in the fabrication of a fiber-reinforced polymer composite laminate. Some glass fibers were replaced with carbon fibers to serve as electrodes in the sensing layer, and the PVDF/GNP micro-nanocomposite membrane was embedded in the laminate to confer multifunctional piezoelectric self-sensing ability. The self-sensing composite laminate has both favorable mechanical properties and sensing ability. The effects of different concentrations of modified multiwalled carbon nanotubes (CNTs) and GNPs on the morphology of PVDF fibers and the β-phase content of the membrane were investigated. PVDF fibers containing 0.05% GNPs were the most stable and had the highest relative β-phase content; these fibers were embedded in glass fiber fabric to prepare the piezoelectric self-sensing composite laminate. To test the laminate's practical application, four-point bending and low-velocity impact tests were performed. The results revealed that when damage occurred during bending, the piezoelectric response changed, confirming that the piezoelectric self-sensing composite laminate has preliminary sensing performance. The low-velocity impact experiment revealed the effect of impact energy on sensing performance.

In-situ growth of robust and superhydrophilic nano-skin on electrospun Janus nanofibrous membrane for oil/water emulsions separation

It is difficult for composite fibrous membranes to achieve up to 99.5% separation efficiency for oil/water emulsions under cycling separation. Herein, a simple method is developed to in-situ grow surperhydrophilic nanocoating on a single electrospun polyvinylidene fluoride (PVDF) fiber surface for fabricating asymmetric wettable Janus PVDF fibrous membranes. Particularly, polysaccharide fluids with zwitterionic polymer chains are generated from the nanofiber subsurface in an inside-out way during the electrospinning process, forming the robust superhydrophilic nanocoating (<5°) under a synergistic effect of both the electric field force and self-migration feature of N-carboxymethyl chitosan fluids (CMCfs). Benefiting from opposite wettability of the PVDF Janus membrane, the results show that the as-prepared Janus membranes with asymmetrical wettability exhibit excellent separation efficiency (S/E) (>99.5 %), a high flux (up to 4325 L m−2 h−1 bar−1), antibacterial activity (>99%) and antifoul properties. Moreover, the obtained Janus membranes own surprising flux cycling stability and retained 99.5% separation efficiency after 12 cycles without any treatment, indicating that the multi-arm polysaccharide fluids acted as the water channel in such membrane and accelerated the flow of water molecules. The Janus PVDF composite membranes have potential applications for oily wastewater treatment and water purification in the future.