Fabrication of a polyvinylidene fluoride cactus-like nanofiber through one-step electrospinning

Surface modification of fibers has attracted significant attention in different areas and applications. In this work, polyvinylidene fluoride (PVDF) cactus-like nanofibers were directly produced via electrospinning at a high relative humidity (RH) of 62%. The formation mechanism of the cactus structure was demonstrated. The effects of the RH on the fabrication of the cactus structure, crystalline phases, mechanical properties, hydrophobicity, and piezoelectric properties of the PVDF nanofibers were investigated. The results showed that the cactus-like nanofibers have a high crystallinity (ΔX_c), and an outstanding water contact angle (WCA), as well as good electrical outputs. We believe that the PVDF cactus structure can be used in many applications such as energy harvesting and self-cleaning surfaces.

A novel PVDF cactus-like nanofiber was directly electrospun. The mechanism of formation, properties, and possible applications were demonstrated.     

Effect of dehydrofluorination reaction on structure and properties of PVDF electrospun fibers

Piezoelectric nanosensors were prepared with a novel type of dehydrofluorinated poly(vinylidene fluoride) (PVDF) nanofibrous membrane. With the synergistic effect of the dehydrofluorination reaction and applied high voltage electric field, the piezoelectric and energy storage properties of fibrous membranes attained great improvement. It was found that the simultaneous introduction of conjugated double bonds to the backbone of PVDF which was accompanied with the elimination of HF, resulted in the decrease of its molecular weight, solution viscosity and hydrophobicity. The crystalline phase, diameter, piezoelectric and energy storage properties of electro-spun PVDF nanofiber membranes significantly depend on the degree of HF elimination in dehydrofluorinated PVDF. The dehydrofluorinated PVDF with 5 hours of reaction exhibits the highest discharged energy density (W_rec) and energy storage efficiency (η), but excessive dehydrofluorination reaction is unfavorable to the energy storage properties. In addition, the dehydrofluorinated PVDF fiber membrane-based nanosensor possesses a larger electrical throughput (open circuit voltage of 30 V, which is three time that of the untreated PVDF), indicating that the introduction of double bonds can also improve the piezoelectric properties of PVDF nanofibers.

A piezoelectric nanosensor was prepared with a novel type of dehydrofluorinated poly(vinylidene fluoride) (PVDF) nanofibrous membrane.     

Significant enhancement of dielectric permittivity and percolation behaviour of La2−xSrxNiO4/poly(vinylidene fluoride) composites with different Sr doping concentrations

The percolation behaviour and dielectric properties of La_2−xSr_xNiO₄ (LSNO)/poly(vinylidene fluoride) (PVDF) composites with different Sr doping concentrations were investigated. The semiconducting LSNO filler particles with x = 0.2 (LSNO-1) and x = 0.4 (LSNO-2) were prepared using a chemical combustion method. The microstructures, thermal properties, and phase compositions of the polymer composites and filler particles were systematically investigated. The conductivity of the LSNO fillers increased with the Sr content and had an important impact on the dielectric properties of the LSNO/PVDF composites. The percolation threshold of the LSNO-2/PVDF composite was lower than that of the LSNO-1/PVDF composite. An ultra-high dielectric permittivity (ε′) of 3384.7 (at 1 kHz and room temperature), which was approximately 340 times higher than that of pure PVDF, was obtained for the LSNO-2/PVDF composite with a filler volume fraction of 25 vol%. The enhanced dielectric properties were attributed to interfacial polarisation at the semiconductor–insulator interface, a micro-capacitor model, and the intrinsically remarkable dielectric properties of the LSNO ceramic.

The percolation behaviour and dielectric properties of La_2−xSr_xNiO₄ (LSNO)/poly(vinylidene fluoride) (PVDF) composites with different Sr doping concentrations were investigated.     

Preparation of PVDF/FMBO composite electrospun nanofiber for effective arsenate removal from water

In this study, novel electrospun nanofibers (NFs) composed of organic polyvinylidine fluoride (PVDF) and inorganic Fe–Mn binary oxide (FMBO) nanoparticles were fabricated using an electrospinning technique for adsorptive decontamination of As(v) from polluted water. The NFs were prepared with doped solutions consisting of different weight ratios of PVDF/FMBO, in a NF matrix, ranging from 0 to 0.5. SEM, XRD, FTIR and TEM then characterized the NFs and FMBO particles. The XRD analysis indicated successful impregnation of FMBO nanoparticles in the NF matrix of the NFs investigated. An As(v) adsorption capacity as high as around 21.32 mg g⁻¹ was obtained using the NF containing the highest amount of FMBO nanoparticles (designated as PVDF/FMBO 0.5). Furthermore, the adsorptive performance of the PVDF/FMBO 0.5 nanofiber could be easily regenerated using diluted alkaline solution (NaOH and NaOCl).

In this study, novel electrospun nanofibers composed of organic polyvinylidine fluoride and inorganic Fe–Mn binary oxide nanoparticles were fabricated using an electrospinning technique for adsorptive removal of As(v) from polluted water.     

Fabrication of tough,anisotropic, chemical-crosslinker-free poly(vinyl alcohol) nanofibrous cryogels via electrospinning

PVA hydrogels with anisotropic structures have many biomedical applications; however, the hydrophilicity of PVA nanofibers degrades their mechanical properties, and the residual unreacted chemical crosslinkers are disadvantageous for medical use. Therefore, maintaining the stability of aqueous solutions without using crosslinkers is essential while synthesizing electrospun anisotropic PVA nanofibers. Herein, we developed a novel fabrication method for synthesizing tough, anisotropic, and chemical-crosslinker-free nanofibrous cryogels composed of poly(vinyl alcohol) (PVA) and glycerol (Gly) via electrospinning in conjunction with freeze–thawing treatment. Wide-angle X-ray diffraction, attenuated total reflection Fourier-transform infrared spectroscopy, and differential scanning calorimetry analysis revealed an enhanced crystallinity of the PVA and hydrogen bonds in the PVA/Gly nanofibers after freeze–thawing, thereby leading to improved stability of the PVA/Gly nanofiber in water. The scanning electron microscopy observation and tensile tests revealed that the addition of Gly improved both the orientation and the mechanical properties. The values of the toughness parallel and vertical to the fiber axis direction were 4.20 ± 0.63 MPa and 2.17 ± 0.27 MPa, respectively, thus revealing the anisotropy of this mechanical property. The PVA/Gly nanofibrous cryogel consisted of physically crosslinked biocompatible materials featuring toughness and mechanical anisotropy, which are favorable for medical applications including tissue engineering.

Fabrication of tough, anisotropic, and chemical crosslinker-free nanofibrous cryogels made from poly(vinyl alcohol) and glycerol via electrospinning in conjunction with freeze-thawing treatment which would be favorable for medical applications.     

Fabrication of PVDF/graphene composites with enhanced β phase via conventional melt processing assisted by solid state shear milling technology

The β-phase crystal, which decides the final electric properties of poly(vinylidene fluoride) (PVDF), is extremely difficult to obtain via conventional melt processing due to its thermal instability. In this work, with the assistance of our independently developed solid state shear milling (S³M) technology, which could provide multiple stresses and form a micro-stretching field on PVDF to promote the transformation of more α phase to β phase, PVDF/graphene (PVDF/GP) composite with relatively higher β phase (42.2%), higher than that directly prepared by melt blending without S³M (33.0%), and dielectric properties was achieved through conventional melt extrusion and injection. When the GP content was 1.0 wt%, the dielectric constant of the composite was 465 at 1000 Hz, about 42 times that of pure PVDF. The special squeezing and shearing forces of S³M also realized the exfoliation of GP as well as the solid grafting of GP layers on PVDF molecules, improving the dispersion of GP layers in PVDF and making them effectively exert their heterogeneous nucleation as well as enhancement effects on PVDF, thus increasing the crystallinity, thermal stability and mechanical properties of the composites.

With the assistance of our independently developed solid state shear milling (S³M) technology, PVDF/GP composite with relatively high β phase (42.2%), higher than that directly gotten by melt blending (33.0%), were achieved via common melt process.     

Free volume dependence of the dielectric constant of poly(vinylidene fluoride) nanocomposite films

The free volume effects on the dielectric properties of the polymer are ambiguous, and the quantitative effect of free volume on the dielectric properties has rarely been systematically studied, especially in the high-elastic state dipolar (HESD) polymer. In this work, the free volume of dipolar poly(vinylidene fluoride) (PVDF) is regulated by the addition of Al₂O₃, which greatly increase the size of free volume holes. Then the effect of free volume on the dielectric properties of PVDF/Al₂O₃ composites is discussed. The greatly enlarged size of free volume holes is believed to potentially generate disparate effects on dielectric constant under different frequencies in such kinds of HESD polymer-based composites, bringing about more remarkable frequency dependence of the dielectric constant. The influence of atomic-scale microstructure based on free volume further clarifies the free volume effects on the dielectric properties and provides valuable insights for the research of dielectric behaviour of polymer composites, which is constructive to design novel dielectric materials and further optimize the dielectric properties of dipolar dielectric polymer composites.

The size variation of free volume holes is found to potentially generate disparate effects on dielectric constant under different frequencies in high-elastic state dipolar poly(vinylidene fluoride).     

Construction of anisotropic fluorescent nanofibers assisted by electro-spinning and its optical sensing applications

Fixing the gap between “nano-scaled” pieces and “product-scale” materials, devices or machines is an ineluctable challenge that people have to tackle. Herein, we show that combining self-assembly and electrospinning processes results in the fabrication of anisotropic fluorescent nanofibers (PDI@PVDF) in which the well-defined rod-like perylene bisimide derivative assemblies are embedded in a highly oriented way along the axis of the poly(vinylidene fluoride) (PVDF) fiber. Compared to fragile individual PDI assemblies, the electrospinning anisotropic fluorescent PDI@PVDF nanofibers not only maintain high sensitivity for aniline vapour but also exhibit an unexpected short response time for both quenching and recovering. The results demonstrate that electrospinning assistance is a versatile and effective strategy to maintain the anisotropy of fluorescent nanomaterials, building a bridge between self-assembled nano-rods and practical materials.

Anisotropic fluorescent nanofibers constructed from the self-assembled perylene bisimide derivative and poly(vinylidene fluoride) show high sensitivity and short response time to aniline vapor.     

Flexible hybrid structure piezoelectric nanogenerator based on ZnO nanorod/PVDF nanofibers with improved output

This study aimed to develop a novel hybrid piezoelectric structure based on poly(vinylidene difluoride) nanofibers (PVDF NFs) and zinc oxide nanorods (ZnO NRs) which eliminate the need for post poling treatment in such hybrid structures. Mechanism of electrical performance enhancement of the hybrid structure is also discussed in this paper. To study the effect of hybridization on piezoelectric performance, pristine ZnO NRs and pristine PVDF NF nanogenerators were also fabricated. The piezoelectric performance of these three nanogenerators was evaluated under periodic deformation at low frequency. The output power of the hybrid structure was found to be enhanced compared to pristine ZnO NRs and PVDF NFs nanogenerators. Such simple hybrid devices that do not need to complicated post poling treatment are more efficient than previous hybrid PVDF/ZnO nanogenerators for practical application. This improved piezoelectric nanogenerator is expected to enable various applications in the field of self-powered devices and wearable energy harvesting to harvest mechanical energy from the human activities.

A novel hybrid piezoelectric structure based on electrospun PVDF NFs and vertically grown ZnO nanorods is presented as a promising nanogenerator to convert mechanical movement more efficiently into electricity for practical applications.     

Silver sulfadiazine loaded zein nanofiber mats as a novel wound dressing

In this report a novel antibacterial wound dressing was prepared and then characterized for required testing. We loaded silver sulfadiazine (AgSD) for the first time by electrospinning. AgSD was added in zein (0.3%, 0.4%, 0.5%, and 0.6% by weight) and was electrospun to fabricate nanofiber mats for wound dressings. Nanofiber mats were characterized by Fourier transform infrared spectroscopy (FTIR) to check if there was any chemical reaction between AgSD and zein. Morphological properties were analyzed by Scanning Electron Microscopy (SEM), which showed uniform nanofibers without any bead formation. The diameter of the nanofibers gradually decreased with an increase in the amount of AgSD, which can be associated with strong physical bonding between zein and AgSD. Thermal properties of nanofiber mats were analyzed by Thermogravimetric Analysis (TGA). X-Ray Diffraction (XRD) further demonstrated the crystalline structure of the nanofiber mats, and X-ray Photoelectron spectroscopy (XPS) was performed to confirm Ag and S contents in the prepared wound dressings. In order to investigate antibacterial properties, a disc diffusion method was employed. Bacillus and E. coli bacteria strains were used as Gram-positive and Gram-negative strains respectively. The antibacterial effectiveness of AgSD released from zein nanofibers was determined from the zone inhibition of the bacteria. The antibacterial activity of zein nanofibers loaded with drug was observed with both strains of bacteria in comparison to a control. Excellent antibacterial efficacy was attributed to the sample with 0.6% AgSD. Excellent release properties were also associated with the sample with 0.6% AgSD in zein nanofibers. Keeping in mind the abovementioned characteristics, prepared nanofiber mats would be effective for application in wound dressings.

In this report a novel antibacterial wound dressing was prepared and then characterized for required testing. We loaded silver sulfadiazine (AgSD) for the first time by electrospinning.     

New surgical meshes with patterned nanofiber mats

Abdominal wall hernia repair is one of the most common general surgeries nowadays. Surgical meshes used in hernia repair indeed improved the outcomes, but complications like chronic pain or hernia recurrence partly caused by mechanical mismatch cannot be ignored. This work designed six warp-knitted polypropylene (PP) meshes and found the properties of surgical meshes could be improved to better mimic the performances of human abdominal wall by designing meshes with appropriate textile structures. Poly-caprolactone was electrospun onto newly designed PP meshes and formed a thin layer of patterned nanofiber mat. The pattern of nanofiber mats was affected by the structure of meshes. Diverse nanofiber morphology (straight aligned, straight random or spiral random pattern) and fiber diameters (50–70 nm ultra-thin nanofibers or from 330 nm to 700 nm nanofibers) were observed in different regions of a single patterned nanofiber scaffold. The addition of electrospinning nanofibers enhanced cell adherence and proliferation as compared with naked PP meshes. Cell actin filaments spread along the nanofibers and formed a morphology exactly similar with the patterned mats on day 7. Furthermore, cells on thin and aligned patterned nanofibers showed much more elongation and better orientation than that of the spiral random fibers, suggesting that cell morphology can be altered by changing the patterns of scaffolds. This study helps us in further understanding the properties of hernia repair meshes with their textile structures and the biological interactions of cells with different substrates in order to develop new biomedical scaffolds with desired properties.

Newly designed warp-knitted meshes with different textile parameters and the interactions between cell and patterned nanofiber mats and different meshes.     

Preparation of poly(lactic acid)/graphene oxide nanofiber membranes with different structures by electrospinning for drug delivery

Nanofiber membranes display promising potential in biomedical fields, especially as scaffolds for drug delivery and tissue engineering. The structures and components of nanofibers play crucial roles in improving the mechanical properties and drug-releasing performance of nanofiber membranes. In this work, poly(lactic acid) (PLA)/graphene oxide (GO) nanofiber membranes with different structures (single-axial and co-axial structure) were prepared by electrospinning. The morphologies, structures, and mechanical properties of the as-prepared nanofiber membranes were characterized and compared. Furthermore, the drug-releasing performance of the as-prepared nanofiber membranes with different structures was evaluated by using an organic dye (Rhodamine B, RhB) as a drug model. Results show that the addition of GO not only significantly improved the thermal stability and mechanical properties of the PLA nanofiber membranes, but also promoted the cumulative release and release rate of RhB from nanofiber membranes. At the same GO concentration, the nanofiber membrane with the co-axial structure displayed a higher tensile strength and Young''s modulus, but exhibited a lower cumulative release and release rate. The formation of the co-axial structure is beneficial in suppressing the initial burst release of RhB from nanofiber membranes.

PLA/GO nanofiber membrane with the co-axial structure exhibited the improved mechanical properties, which is also beneficial to separately loading different drugs in core-/sheath-structure and suppressing the initial burst release of drugs.     

N-Doped carbon nanoparticles on highly porous carbon nanofiber electrodes for sodium ion batteries

Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber electrodes were successfully synthesized via combining centrifugal spinning, chemical polymerization of pyrrole and a two-step heat treatment. Nanoparticle-on-nanofiber morphology with highly porous carbon nanotube like channels were observed from SEM and TEM images. Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber (N-PCNF) electrodes exhibited excellent cycling and C-rate performance with a high reversible capacity of around 280 mA h g⁻¹ in sodium ion batteries. Moreover, at 1000 mA g⁻¹, a high reversible capacity of 172 mA h g⁻¹ was observed after 300 cycles. The superior electrochemical properties were attributed to a highly porous structure with enlarged d-spacings, enriched defects and active sites due to nitrogen doping. The electrochemical results prove that N-PCNF electrodes are promising electrode materials for high performance sodium ion batteries.

Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber electrodes were successfully synthesized via combining centrifugal spinning, chemical polymerization of pyrrole and a two-step heat treatment.     

A core–shell structured polyacrylonitrile@poly(vinylidene fluoride-hexafluoro propylene) microfiber complex membrane as a separator by co-axial electrospinning

A novel and facile core–shell structured polyacrylonitrile@poly (vinylidene fluoride-hexafluoro propylene) (PAN@PVDF-HFP) microfiber complex membrane was designed and fabricated via co-axial electrospinning, which was used as a separator in lithium-ion batteries. Poly(vinylidene fluoride-co-hexafluoro propene) (PVDF-HFP) and polyacrylonitrile (PAN) were used as the shell (outer) layer and core (inner), respectively. Structure, surface morphology, porosity, and thermal properties of the core–shell structured microfiber membranes were investigated. Compared with the traditional commercial porous polyethylene (PE) separator, the PAN@PVDF-HFP microfiber complex membranes exhibited higher porosity, superior thermal stability, better electrolyte wettability and higher ionic conductivity. As a consequence, batteries assembled with the PAN@PVDF-HFP microfiber complex membrane display better cycling stability and superior rate performance compared to those with the PE separator.

A novel and facile core–shell structured polyacrylonitrile@poly (vinylidene fluoride-hexafluoro propylene) (PAN@PVDF-HFP) microfiber complex membrane was designed and fabricated via co-axial electrospinning.     

Anhydrous proton conductivity of electrospun phosphoric acid-doped PVP-PVDF nanofibers and composite membranes containing MOF fillers

A high-temperature proton exchange membrane was fabricated based on polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP) blend polymer nanofibers. Using electrospinning method, abundant small ionic clusters can be formed and agglomerated on membrane surface, which would facilitate the proton conductivity. To further enhance the conductivity, phosphoric acid (PA) retention as well as mechanical strength, sulfamic acid (SA)-doped metal–organic framework MIL-101 was incorporated into PVP-PVDF blend nanofiber membranes. As a result, the anhydrous proton conductivity of the composite SA/MIL101@PVP-PVDF membrane reached 0.237 S cm⁻¹ at 160 °C at a moderate acid doping level (ADL) of 12.7. The construction of long-range conducting network by electrospinning method combined with hot-pressing and the synergistic effect between PVP-PVDF, SA/MIL-101 and PA all contribute to the proton conducting behaviors of this composite membrane.

A composite SA/MIL101@PVP-PVDF membrane was fabricated via electrospinning and reached a conductivity of 0.237 S cm⁻¹ at 160 °C with a moderate acid doping level (12.7).     

Ferroelectric P(VDF-TrFE)/POSS nanocomposite films: compatibility,piezoelectricity, energy harvesting performance,and mechanical and atomic oxygen erosion

Poly(vinylidene difluoride) (PVDF) and its copolymers as the polymers with the highest piezoelectric coefficient have been widely used as sensors and generators. However, their relatively low performances limit their applications in some harsh environments. In this work, piezoelectric poly(vinylidene-trifluoroethylene) P(VDF-TrFE) matrices with different amounts of polyhedral oligomeric silsesquioxane (POSS) were prepared by a low temperature solvent evaporation method and thermal poling. The morphology, surface performance, crystalline phase, and piezoelectric and ferroelectric properties of the nanocomposites were investigated and the influence of POSS on these performances was studied. POSS had good compatibility with P(VDF-TrFE) and did not affect the crystalline phase formation of the matrix. The composites presented good piezoelectric properties. Piezo- and triboelectric nanogenerators were designed and fabricated. The voltage and current outputs were analyzed and the polarization effect was evaluated. The average output voltage and the current density of the matrix were 3 V and 0.5 μA cm⁻² when subjected to a force of 38 N on an area of 1 cm². The mechanical properties of P(VDF-TrFE)/POSS nanocomposites were also studied by the nanoindentation test. The hardness and modulus of samples increased 20% and 17% with a low addition of POSS. Atomic oxygen erosion properties of the composites were numerically simulated by the Monte Carlo method. The erosion cavity shape and depth were compared and studied. The influence of POSS addition on the P(VDF-TrFE) matrix and the associated reinforcing mechanism were analyzed.

Poly(vinylidene difluoride) (PVDF) and its copolymers as the polymers with the highest piezoelectric coefficient have been widely used as sensors and generators.     

Quercetin-gold nanorods incorporated into nanofibers: development,optimization and cytotoxicity

Herein, a polymeric nanofiber scaffold loaded with Quercetin (Quer)–gold nanorods (GNR) was developed and characterized. Several parameters related to loading Quer into GNR, incorporating the GNR-Quer into polymeric solutions, and fabricating the nanofibers by electrospinning were optimized. GNR-Quer loaded into a polymeric mixture of poly(lactic-co-glycolic acid) (PLGA) (21%) and poloxamer 407 (23%) has produced intact GNR-Quer-nanofibers with enhanced physical and mechanical properties. GNR-Quer-nanofibers demonstrated a slow pattern of Quer release over time compared to nanofibers free of GNR-Quer. Dynamic mechanical thermal analysis (DMTA) revealed enhanced uniformity and homogeneity of the GNR-Quer-nanofibers. GNR-Quer-nanofibers demonstrated a high ability to retain water upon incubation in phosphate buffer saline (PBS) for 24 h compared to nanofibers free of GNR-Quer. A cellular toxicity study indicated that the average cellular viability of human dermal fibroblasts was 76% after 24 h of exposure to the nanofibers containing a low concentration of GNR-Quer.

Incorporating GNR-Quer into a mixture of 21% PLGA LMWT and 23% poloxamer 407 produced smooth, intact and uniform electrospun nanofibers with enhanced mechanical properties and hydration potential.     

Fabrication of centrifugally spun prepared poly(lactic acid)/gelatin/ciprofloxacin nanofibers for antimicrobial wound dressing

Centrifugal spinning is a novel technology for producing ultrafine fibers in high yield with diameters ranging from micro to nanometers. The obtained fibers have potential applications in the field of tissue engineering, wound dressing, and biomedicine etc. In this paper, a system of poly(lactic acid)/gelatin (PLA/GE) nanofibers loaded with ciprofloxacin (CPF) drug for wound dressings were successfully prepared by centrifugal spinning. The nanofibers were characterized by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). In addition, the nanofibers'' properties in terms of hydrophilicity, antibacterial properties and in vitro drug release were further investigated. The results showed that the CPF drug was successfully loaded and in an amorphous state in the PLA/GE nanofibers, the surface of the nanofibers was smooth and the nanofibers'' diameter became large after the drug was loaded. The thermal stability of the nanofiber was reduced while the hydrophilicity was improved. Antibacterial and in vitro drug release experiments showed that the nanofibers have obvious antibacterial properties and have the positive effect of sustained release of the drug. Drug-loaded PLA/GE nanofibers could be good candidates for wound dressing.

Centrifugal spinning is a novel technology for producing ultrafine fibers in high yield with diameters ranging from micro to nanometers.     

Nanofibers with diameter below one nanometer from electrospinning

Sub-nanometer materials have received wide attention due to their unique properties in recent years. Most studies focus on the preparation and properties investigation of the inorganic sub-nanometer materials, while there are few reports on organic especially polymeric sub-nanometer materials such as sub-nanometer fiber due to the obstacles with respect to fabricating such small nanofibers. In this work we prepare PAA nanofibers with diameters ranging from hundreds of nanometers down to sub-nanometer via electrospinning from a polyamic acid (PAA) with ultrahigh molecular weight. The morphologies and size of the electrospun ultrathin nanofibers are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). AFM images combined with theoretic calculations show that sub-nanometer fiber of approximate 0.17–0.63 nm only containing one molecular chain was generated via electrospinning from ultra-dilute PAA solutions for the first time. These quite small sub-nanometer fibers would open a new area of electrospinning and provide further explorations on the production and application of electrospun sub-nanometer fibers with single molecular chains.

Super-fine nanofibers with diameter below 1 nanometer are prepared by electrospinning from ultra-dilute solutions.     

Application of ANN modeling techniques in the prediction of the diameter of PCL/gelatin nanofibers in environmental and medical studies

Prediction of the diameter of a nanofiber is very difficult, owing to complexity of the interactions of the parameters which have an impact on the diameter and the fact that there is no comprehensive method to predict the diameter of a nanofiber. Therefore, the aim of this study was to compare the multi-layer perceptron (MLP), radial basis function (RBF), and support vector machine (SVM) models to develop mathematical models for the diameter prediction of poly(ε-caprolactone) (PCL)/gelatin (Gt) nanofibers. Four parameters, namely, the weight ratio, applied voltage, injection rate, and distance, were considered as input data. Then, a prediction of the diameter for the nanofiber model (PDNFM) was developed using data mining techniques such as MLP, RBFNN, and SVM. The PDNFM_MLP is introduced as the most accurate model to predict the diameter of PCL/Gt nanofibers on the basis of costs and time-saving. According to the results of the sensitivity analysis, the value of the PCL/Gt weight ratio is the most significant input which influences PDNFM_MLP in PCL/Gt electrospinning. Therefore, the PDNFM model, using a decision support system (DSS) tool can easily predict the diameter of PCL/Gt nanofibers prior to electrospinning.

A new tool for prediction the diameter of nanofibers is presented: the use of adaptive modeling techniques to predict fiber diameter and study the impact of electrospinning process parameters on electrospinning fiber diameter.