PVDF Nanofibers Research Articles

Self-roughened omniphobic coatings on nanofibrous membrane for membrane distillation

Novel omniphobic electrospun nanofibrous membranes (ENMs) for direct contact membrane distillation (DCMD) were fabricated by electrospinning poly(vinylidene fluoride) (PVDF) nanofibers and followed by directly functionalizing the fiber surface with long-chained fluorododecyltrichlorosilane (FTCS) via solution immersion without any assistance of roughening treatments. The morphologies of polymerized fluorododecyltrichlorosilane (PFTCS) coated PVDF nanofibers evolved from the newly budding willow twigs with tiny bumps, to vigorous buds and then to intertwined fillets with the increase of FTCS concentration, which could serve as a robust barrier to low-surface-tension liquid penetration. By constructing hierarchically re-entrant structures of low-surface-energy PFTCS coating layer onto the PVDF nanofibers, the resultant porous ENMs were endowed with omniphobic property, low water-adhesion property, remarkable mechanical property, and superior durability in harsh circumstances as well as good breathability. The comprehensive investigations on structural attributes (such as the liquid entry pressure, pore size, porosity and gas permeability), long-term MD stability and DCMD performance in presence of surfactants were carried out. Significantly, the resultant omniphobic PFTCS/PVDF membrane exhibited a competitive permeate vapor flux of 36.9 kg/(m2 h) in highly salty solution (3.5 wt% NaCl salt feed; ΔT = 40 °C) over 24 h operation and also demonstrated robust DCMD performance in presence of surfactants. Compared with the commercial PVDF MD membranes, this simple and scalable strategy had great potential for MD applications.

Hydrophilically modified poly(vinylidene fluoride) nanofibers incorporating cellulose acetate fabricated by colloidal electrospinning for future tissue‐regeneration applications

A composite consisting of mechanically strong Poly(vinylidene fluoride) (PVDF) and biochemically favorable Cellulose acetate (CA) nanofibers can be considered as an excellent choice due to their excellent mechanical properties of PVDF and desirable biological properties of CA. However, preparing nanofibers of composites, involving CA requires the use of harsh acidic solutions and high temperatures, which can have serious consequences on a bio‐aspect of CA. In this study, we have successfully prepared suitable solutions comprising of PVDF and CA in dimethylformamide. Subsequently, these solutions were directly ejected out as nanofibers during the process of electrospinning. The nanofibers synthesized were characterized for physicochemical properties by scanning electron microscopy, contact angle, Fourier transform infrared, thermogravimetric, and X‐ray diffraction spectroscopy. The results revealed that CA can be easily introduced in PVDF nanofibers, using a single solvent (i.e., dimethylformamide). The introduced strategy can favorably preserve the inherent biological nature of CA. Moreover, the nanofibers prepared using this methodology was investigated for cell toxicity and cell attachment properties. These studies were carried to figure out the beneficial features shown by the CA to suppress inherent toxicity of PVDF nanofibers. The results of these studies proved that NIH 3T3 fibroblasts upon incubation in the presence of composite nanofibers containing CA can proliferate well when compared to pristine PVDF nanofibers. POLYM. COMPOS., 40:1619–1630, 2019. © 2018 Society of Plastics Engineers

All-Organic High-Performance Piezoelectric Nanogenerator with Multilayer Assembled Electrospun Nanofiber Mats for Self-Powered Multifunctional Sensors

Rapid development of wearable electronics, piezoelectric nanogenerator (PNG), has been paid a special attention because of its sustainable and accessible energy generation. In this context, we present a simple yet highly efficient design strategy to enhance the output performance of an all-organic PNG (OPNG) based on multilayer assembled electrospun poly(vinylidene fluoride) (PVDF) nanofiber (NF) mats where vapor-phase polymerized poly(3,4-ethylenedioxythiophene)-coated PVDF NFs are assembled as electrodes and neat PVDF NFs are utilized as an active component. In addition to the multilayer assembly, electrode compatibility and durability remain a challenging task to mitigate the primary requirements of wearable electronics. A multilayer networked three-dimensional structure integrated with a compatible electrode thereby provides enhanced output voltage and current (e.g., open-circuit voltage, Voc ≈ 48 V, and short-circuit current, Isc ≈ 6 μA, upon 8.3 kPa of the applied stress amplitude) with superior piezoelectric energy conversion efficiency of 66% compared to the single-mat device. Besides, OPNG also shows ultrasensitivity toward human movements such as foot strikes and walking. The weight measurement mapping is critically explored by principal component analysis that may have enormous applications in medical diagnosis to smart packaging industries. More importantly, fatigue test under continuous mechanical impact (over 6 months) shows great promise as a robust wearable mechanical energy harvester.

Mechanisms for Enhancing Polarization Orientation and Piezoelectric Parameters of PVDF Nanofibers

AbstractMany emerging applications strongly demand flexible and efficient electromechanical conversion materials. Polymeric piezoelectric materials, with ability of large area and low temperature processing, are attractive to obtain wide applications for electromechanical sensors, transducers, and mechanical energy harvesters. A major drawback of the polymeric piezoelectric materials is their much lower piezoelectric performance property, such as piezoelectric strain coefficient, than their ceramic counterparts. Here, outstanding piezoelectric performance properties with giant effective strain and voltage coefficients of −116 pm V−1 and −1180 V mm N−1 are achieved in electrospun polyvinylidene fluoride nanofiber films from the precursor solution modified with hydrated salt. The experimental results and theoretical analysis clarify a synergistic interactive role from the hydrated salt and the electric field during electrospinning, effectively leading to polarization enhancement and alignment, and hence the giant macroscopic piezoelectric coefficients in the obtained electrospun fiber films. The demonstrated results and the understanding on the underlying mechanism exhibit the potential and strategy in achieving high‐performance functional materials through dedicated control on their nanostructures and polarizations.

Organo-lead halide perovskite regulated green light emitting poly(vinylidene fluoride) electrospun nanofiber mat and its potential utility for ambient mechanical energy harvesting application

Methylammonium lead bromide (CH3NH3PbBr3) (MAPbBr) has been synthesized and then introduced in the poly(vinylidene fluoride) (PVDF) nanofiber made by the process of electrospinning. The β-phase composition, degree of crystallinity as well as mechanical, optical and energy harvesting properties of this composition has been investigated. Increased electroactive phase composition (91%) and dramatic improvement in tensile strength of the PVDF nanofiber mats is found by the addition of MAPbBr. This increase in electroactive phase composition can play a significant role in the enhancement of output power which is a premiere observation. The acoustic nanogenerator (ANG) made from MAPbBr doped PVDF nanofibers (NFs) can also be utilized in energy scavenging from acoustic vibration with a higher degree of acoustic sensitivity (~ 13.8 V Pa−1) and efficiency (58.5%). This suggests that ANG could be a potential tool for power generation in portable electronics. This fact may open up the prospect of using the MAPbBr doped PVDF electrospun nanofibers, with their multifunctional properties such as vibration sensitivity, piezoelectric energy harvesting, green light emission capability (quantum yield ~ 32.6%), for various promising applications in portable electronics, noise detection and security monitoring.

A brief review on piezoelectric PVDF nanofibers prepared by electrospinning

ABSTRACTPoly(vinylidene fluoride) (PVDF) has been a kind of particularly attractive piezoelectric materials for its excellent piezoelectric property. It has been proven that the piezoelectric property of PVDF can be improved by electrospinning. Recently, the technical innovations on the multiple aspects of preparing electrospun PVDF nanofibers such as collecting equipment and the pretreatment emerged in endlessly. The article introduces electrospinning briefly firstly and the second part of the paper introduces some recent research on the preparation of electrospun PVDF nanofibers. The researches about promising applications using electrospun PVDF nanofibers involve biomedicine, sensors, and energy harvesting due to its flexibility, biocompatibility, and outstanding performance. The last part of the paper reviews the typical research.

Synergism of Electrospinning and Nano-alumina Trihydrate on the Polymorphism, Crystallinity and Piezoelectric Performance of PVDF Nanofibers

Poly(vinlylidene fluoride) (PVDF) is known for its electroactive phases, which can be nucleated by incorporating nanoparticles into PVDF to enhance its piezoelectric performance. In this study, the synergistic effect of electrospinning and nano alumina trihydrate (ATH) filler was used to enhance the electroactive β phase of PVDF. Electrospun nanofibers of PVDF/ATH nanocomposite (PANCF) were synthesized with different loadings of ATH. The presence of ATH enhances the surface charges of the electrospun droplets, leading to thinner fibers. The highest β-phase content was found to be 70.1% for PANCF with 10% ATH. The piezoelectric performance of the nanofiber mats was studied using an indigenous setup. The highest voltage output of 840 mV was produced by PANCF with 10% ATH. These nanofibers could be a promising material in the field of sensors, actuators and energy-harvesting applications.

Porous PVdF/GO Nanofibrous Membranes for Selective Separation and Recycling of Charged Organic Dyes from Water.

Graphene oxide (GO) membranes are robust and continue to attract great attention due to their fascinating properties, despite their potential issues regarding stability and selectivity in aqueous-phase processing. That being said, however, the functional moieties of GO could be used for membrane surface modification, while ensuring simultaneous removal and recycling of industrial organic dyes. Herein, we present a versatile porous structured polyvinylidene fluoride-graphene oxide (PVdF-GO) nanofibrous membranes (NFMs), prepared by using simple and straightforward electrospinning approach for selective separation and filtration. The GO nanosheets were distributed homogeneously throughout the PVdF nanofiber, regulating the surface morphology and performance of PVdF-GO NFM. The PVdF-GO NFMs possesses high mechanical strength and surface free energy (SFE), consequently resulting high permeation and filtration efficiency as compared to PVdF NFM. The selectivity (99%) toward positively charged dyes based on electrostatic attraction, while maintaining rejection (100%) for negatively charged dye from mixed solutions highlight the role of GO in PVdF-GO NFM, owing to uniform pores and negatively charged surface. In addition, the actual efficiency of NFMs could be recovered easily up to three consecutive filtration cycles by regeneration, thereby assuring high stability. The high permeation, purification and filtration efficiency, good stability and recycling of PVdF-GO NFMs are promising for use in practical water purification and applications, particularly for selective filtration and recycling of dyes.

Sensitive and Flexible Polymeric Strain Sensor for Accurate Human Motion Monitoring.

Flexible electronic devices offer the capability to integrate and adapt with human body. These devices are mountable on surfaces with various shapes, which allow us to attach them to clothes or directly onto the body. This paper suggests a facile fabrication strategy via electrospinning to develop a stretchable, and sensitive poly (vinylidene fluoride) nanofibrous strain sensor for human motion monitoring. A complete characterization on the single PVDF nano fiber has been performed. The charge generated by PVDF electrospun strain sensor changes was employed as a parameter to control the finger motion of the robotic arm. As a proof of concept, we developed a smart glove with five sensors integrated into it to detect the fingers motion and transfer it to a robotic hand. Our results shows that the proposed strain sensors are able to detect tiny motion of fingers and successfully run the robotic hand.

Characterization of triple electrospun layers of PVDF for direct contact membrane distillation process

Recently, electrospinning technique was applied successfully to fabricate porous hydrophobic membranes for MD applications. In this work, a novel triple layer configuration with diameter gradient for PVDF nanofiber membranes is proposed, with the objective of to minimize mass transfer resistance and heat loss. In outer layers of these membranes, the minimum concentration of PVDF (20 wt%) was used to produce bead-free nanofibers with thinner diameters and middle layers were composed of thicker nanofibers formed at higher polymer concentrations (21.5-26 wt%). Characterization of prepared membranes was conducted by the measurement of porosity, thickness, liquid entry pressure (LEP), scanning electron microscopy (SEM), contact angle, thermal and mechanical properties. Direct contact membrane distillation performance of fabricated membranes was tested using 42 g/L NaCl as feed solution. Water permeate flux of triple layer membranes (27.8-31.5 kg/m2 h) was found to be considerably higher than that obtained from single layer membrane (15.4 kg/m2 h), indicating the proposed configuration can effectively improve evaporation efficiency.

Fabrication and Raman Analysis of Aligned Electrospun PVDF Nanofibers

Fabrication and Raman Analysis of Aligned Electrospun PVDF Nanofibers

Enhancing the Tactile and Near-Infrared Sensing Capabilities of Electrospun PVDF Nanofibers with the Use of Gold Nanocages.

Owing to its piezoelectric and pyroelectric properties, poly(vinylidene fluoride) (PVDF) has been extensively explored for applications related to tactile sensing, energy harvesting, and thermal imaging. However, PVDF cannot be directly used to detect light because of its weak absorption in the visible and near-infrared (NIR) regions, preventing effective conversion from light to heat and then electrical signal. In this work, we address this issue by incorporating Au nanocages (AuNCs) into PVDF nanofibers during electrospinning. The strong and tunable optical absorption associated with AuNCs makes them an effective transducer for converting light to heat and then electrical signal. The presence of AuNCs and the strong electric field inherent to electrospinning both promote the formation of the ferroelectric β phase for maximal piezoelectric and pyroelectric conversions. With the incorporation of AuNCs, the electrospun PVDF nanofibers show enhanced capabilities for tactile and NIR sensing. While the voltage output under the tactile force is increased by 12.6-fold relative to the case of pristine PVDF nanofibers, a voltage output of 7.2 V is achieved when the hybrid device is subjected to the on/off cycles of NIR irradiation by an 808-nm diode laser at a power density of 0.2 W/cm2.

Effect of Source Solution Components on Quality of Electrospun PVDF Nanofibers for Nanogenerator Application

Effect of Source Solution Components on Quality of Electrospun PVDF Nanofibers for Nanogenerator Application

Wettability of PVDF Nanofibers by Plasma Treatment

Wettability of PVDF Nanofibers by Plasma Treatment

An Effective Wind Energy Harvester of Paper Ash-Mediated Rapidly Synthesized ZnO Nanoparticle-Interfaced Electrospun PVDF Fiber

In this paper, we report an innovative technique for the rapid and simple synthesis of ZnO-containing paper ash (ZPA) within 30 min. It is demonstrated that as-synthesized ZPA can be an alternative for conventional semiconducting filler that is used to improve the electroactive β-phase content in the electrospun PVDF nanofiber (NF). Furthermore, the PVDF nanofiber-based nanogenerator (NFNG) that enables a high output voltage of 4.8 V under an exerted wind pressure of 145 Pa is fabricated. In addition, the detection capability of minute wind pressure, even from human mouth blowing, makes the NFNG an active sensor that might be utilized for charging a mobile phone during conversation. Thus, this strategy is expected to be a promising platform for harvesting wind energy that is beneficial for the design of integrated self-powered wearable electronic devices.

Surface morphology and beta-phase formation of single polyvinylidene fluoride (PVDF) composite nanofibers

This study has developed a reliable model to design and engineer PVDF nanofiber in terms of both morphological and fraction of beta-phase content based on response surface methodology (RSM). The model was further used to assess the effect of each individual electrospinning processing parameter as well as their interdependences on the properties of electrospun PVDF nanofibers. Our experimental results highly agreed with the modeling. The results indicated that both morphological and crystalline properties of PVDF are highly affected by electrospinning process parameters, particularly the fraction of beta-phase content. A beadless PVDF nanofiber with the maximum fraction of the beta phase was achieved through a numerical optimization process.

Electrospun poly(vinylidene fluoride) membranes functioning as static charge storage device with controlled crystalline phase by inclusions of nanoscale graphite platelets

Caused by the nature of polymorphism of poly(vinylidene fluoride) (PVDF), crystalline transformation could significantly influence the properties of PVDF. In this work, electrospun PVDF membranes were studied for their tensile properties and static charge storing capacity with controlled crystalline phase. The crystallinity was found to be influenced by inclusions of nanoscale graphite platelet (NGP). Bead-free nanofibers with uniform structure were determined by scanning electron microscopy (SEM). Structural and intermolecular characterizations were performed by SEM and Fourier transform infrared spectroscopy. Analyses of thermal properties were carried out by using differential scanning calorimetry and thermogravimetric analysis. Experimental results showed that NGP inclusions significantly changed the crystallinity of the PVDF nanofibers by inducing a transition of α-crystalline phase to β-crystals and, therefore, increased the thermal stability of the electrospun membranes. Tensile properties of PVDF membranes with and without NGP inclusions were evaluated by a universal testing system. Due to the increased fraction of β-crystals, the tensile strength, failure strain and Young’s modulus of the composite membrane (NGP0.75) were improved by 31.2, 20.5, 132.4%, respectively, in contrast to virgin PVDF. This result indicated the significant development of small fractions of NGP on the tensile properties of the PVDF nanofibers; moreover, the static charge storage ability of electrospun membranes with and without NGP inclusions was evaluated and showed an enhancement caused by the increased β-crystals fractions.

Investigation of the Effect of Nanosilica on Rheological, Thermal, Mechanical, Structural, and Piezoelectric Properties of Poly(vinylidene fluoride) Nanofibers Fabricated Using an Electrospinning Technique

The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline structure of PVDF.

Solution blown biofunctionalized poly(vinylidene fluoride) nanofibers for application in proton exchange membrane fuel cells

In this study, we prepared a novel type of biofunctionalized poly(vinylidene fluoride) (PVDF) nanofibers. Cysteine, a natural amino acid, was grafted onto the surfaces of PVDF nanofibers, The −SH groups of cysteine were then oxidized to −SO3H. The formation of proton-conducting pathways was induced by the −SO3H and COOH groups of the oxidized cysteine chains on the surfaces of the biofunctionalized PVDF nanofibers. Composite membranes were fabricated by impregnating the biofunctionalized PVDF nanofibers with Nafion. Then, the effects of incorporating nanofibers grafted with different amounts of oxidized cysteine on the thermal stability, water uptake dimensional stability, proton conductivity, and single-cell performance of Nafion composite membranes were investigated. The properties of the composite membranes were superior to those of the Nafion membrane. Furthermore, Nafion/PVDF–Cys-30 exhibited the highest proton conductivity of 0.22Scm−1 (80°C), and the maximum power density of 108.42mWcm−2 which was twice than the values of Nafion 117 membrane (51.2mWcm−2) at 60°C under 100% RH. The introduction of biofunctionalized nanofibers significantly improved cell performance, proton conductivity, dimensional stability, and methanol permeability of the membrane.

Biomimetic hydrogel-CNT network induced enhancement of fluid-structure interactions for ultrasensitive nanosensors

Flexible, self-powered, miniaturized, ultrasensitive flow sensors are in high demand for human motion detection, myoelectric prosthesis, biomedical robots, and health-monitoring devices. This paper reports a biomimetic nanoelectromechanical system (NEMS) flow sensor featuring a PVDF nanofiber sensing membrane with a hydrogel infused, vertically aligned carbon nanotube (VACNT) bundle that mechanically interacts with the flow. The hydrogel-VACNT structure mimics the cupula structure in biological flow sensors and gives the NEMS flow sensor ultrahigh sensitivity via a material-induced drag force enhancement mechanism. Through hydrodynamic experimental flow characterization, this work investigates the contributions of the mechanical and structural properties of the hydrogel in offering a sensing performance superior to that of conventional sensors. The ultrahigh sensitivity of the developed sensor enabled the detection of minute flows generated during human motion and micro-droplet propagation. The novel fabrication strategies and combination of materials used in the biomimetic NEMS sensor fabrication may guide the development of several wearable, flexible, and self-powered nanosensors in the future.