Electrospun Web Research Articles

The Production of Hollow Nanofibers from PBS / TPU Blends by Coaxial Electrospinning Method

In this study, the production of hollow Polybutylene Succinate (PBS)/Thermoplastic Polyurethane (TPU) nanofibers as biodegradable nanomaterials with improved mechanical properties were carried out by coaxial electrospinning method. The polymer solutions of pure PBS, pure TPU, and PBS/TPU blends (60/40, 40/60, 20/80 w/w) (as the shell) versus pure Polyvinylpyrrolidone (PVP) (as core) were put together for bi-component nanofibers production. The core structure of nanofibers was dissolved in distilled water. Thus, hollow nanofibers were obtained with the removal of PVP from the structure. Characterization studies (SEM, FTIR, and Tensile tests) of hollow nanofibers were performed. The morphological properties of PBS/TPU blends in ratios of 60/40 and 20/80 were observed as homogeneous and non-adhered fiber structures. It was determined that the hollow PBS/TPU (60/40) mat has the thinnest nanofibers. New bond formations within the interactions of substances as studied in the chemistry of blended electrospun webs were examined with FTIR analysis. Therewithal, this test showed the removal of PVP in the core of all nanofibers. It was observed that the adhered fibers increased the tensile stress and decreased the tensile strain at mechanical test results that were verified also by SEM views. It is suggested that the hollow nanofibers produced by this study can be used in the biomedical field as a biodegradable and breathable wound dressing.

Critical role of the composition of the cell culture medium on cell attachment and viability on PLA biocomposite scaffolds under in vitro assay conditions

In tissue engineering applications 3D scaffolds undertake the function of the native extracellular matrix (ECM) for cell attachment, survival, proliferation, and differentiation. For successful long-term implementation scaffolds need to mimic the ECM in vitro and in vivo. Many studies have focused on protein adsorption as the most critical factor for cell attachment. To improve protein adsorption on polymeric scaffolds various physical and chemical surface modification techniques, such as changing surface porosity, surface energy, and introducing various functional surface chemical groups have been investigated. It is well studied and documented that complex interactions between the biomaterial surface and the cell culture components in in vitro assay conditions define the scaffold performance. In this study influence of in vitro assay components on HepG2 liver cell attachment and proliferation on 3D printed poly(lactic acid) (PLA) scaffolds coated with various polymeric electrospun webs were investigated. MTT assays were performed on the scaffolds by using 3 different cell culture media; (i) basal cell culture medium (DMEM), (ii) DMEM supplemented with 10% albumin, and (iii) DMEM supplemented with 10% fetal bovine serum (FBS). Results obtained have shown dramatic improvement in cell attachment and proliferation in DMEM supplemented with 10% FBS when compared with DMEM and DMEM containing 10% albumin. Our findings clearly demonstrate synergistic effects of all bioactive components present in the FBS medium in significantly improving the HepG2 cell attachment and proliferation on polymeric scaffolds under in vitro conditions, regardless of the substrate structure, composition, and surface properties.

Robust water‐stable poly (ethersulfone)/poly (ethyleneimine) nanofibrous membranes for nitrate adsorption

AbstractNanofibrous media or electrospun webs are widely used as affinity membranes due to their extraordinary properties. In this study, the micro‐nano structure PES/PEI membrane was fabricated by electrospinning. The stability of the membrane during adsorption and washing is very important for affinity membranes. The fabricated web was insolubilized through an optimized crosslinking reaction by glutaraldehyde. Effect of crosslinking time and concentration on adsorption efficiency of adsorbent for nitrate studied using batch experiments. The morphology of the nanofibrous web before and after crosslinking was characterized by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy was used for studying the change in functional groups of PES/PEI composite. Results show that 90 min of crosslinking reaction by immersion method in 0.71% glutaraldehyde in water/acetone medium could successfully insolubilize the polyethyleneimine and change the smooth surface of the nanofibrous web to a rough state with nano spherules. The kinetics studies show that nitrate adsorption by PES/PEI composite follows a pseudo‐second‐order kinetic model. The adsorption isotherm was also investigated using Langmuir and Freundlich models. Results show that the adsorption of nitrate on PES/PEI follows the Langmuir model with a maximum adsorption capacity of 53.47 mg/g which is considered a high value comparing other studies.

Investigation of biodegradability and cellular activity of PCL/PLA and PCL/PLLA electrospun webs for tissue engineering applications.

Biodegradability and cellular activity are key performance indicators that should be prioritized for tissue engineering applications. Biopolymer selection, determination of necessary structural properties, and their synergistic interactions play an active role in obtaining the expected biodegradability and biological activity from scaffolds. In this study, it is aimed to produce electrospun webs with improved biocompatibility by blending polycaprolactone (PCL) with polylactic acid (PLA) and poly-l-lactide (PLLA), and examine the effect of biopolymer selection and blend ratio on the biodegradability and cellular activity of surfaces. In this context, fibrous webs are produced from PCL/PLA and PCL/PLLA blends with a weight ratio of 80/20 and 50/50 and pure polymers of PCL, PLA, and PLLA by electrospinning method and subjected to morphological and biological analyses. The biodegradation tests are carried out hydrolytically while the cell viability and cell proliferation analyses are performed with adult human primary dermal fibroblasts and human umbilical endothelial cells (HUVECs). The results show that the fiber diameters of the fabricated webs ranged from 0.747 to 1.685 μm. At the end of the 5th month, it is observed that the biodegradation rates of the webs blended 50% with PLA and PLLA, in comparison to PCL ones, increase from 3.7% to 13.33% and 7.69%, respectively. On the other hand, cell culture results highlight that the addition of 20% PLA and PLLA improves the cellular activity of both cell types, but increased PLA or PLLA ratio in PCL webs has a negative effect as it makes the structure stiff and brittle.

Tailoring the Porosity and Breathability of Nanofiber Webs with Mesh Size of the Deposition Material

Nano and micro-pores of the electrospun webs provide good moisture vapor transmission rate, while it maintains resistance to pressured air and resistance to liquid for some type of clothing. Laminating a nanofiber web to any textile structure could improve the desired resistance to air permeability with providing excellent breathability. In the present study, hydrophobic thermoplastic polyurethane (TPU) and hydrophilic poly (vinyl alcohol) (PVA) nanofiber webs were produced onto three different chromium sieve wires and then laminated to an interlining fabric and compared in means of pore size, breathability and air permeability. Mesh count of the wires affected the pore size and smallest pore size are belong to 90 mesh wire. The water vapor permeability of the samples varied between 80% and 90% as well as providing relatively low air permeability values. With increasing nanofiber amount, air permeability decreased dramatically.

Fabrication of Mandarin (Citrus reticulate L.) peel essential oil and nano-calcium carbonate incorporated polylactic acid/polyvinylpyrrolidone electrospun webs

Fibrous materials from polylactic acid (PLA) and polyvinylpyrrolidone (PVP) containing mandarin peel essential oil (MPEO) and/or nano-calcium carbonate were prepared by electrospinning process. The electrospun webs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and microbiological tests. IR spectra results indicated the existence of interaction among additives and polymer matrix. Obtained SEM results showed that incorporation of essential oil to the polymer matrix have a remarkable effect on the fiber morphology. Essential oil incorporation increased the fiber diameters. The electrospun composite webs were ineffective against Acinetobacter baumannii, Bacillus subtilis, Escherichia coli, Enterococcus fecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus.

Chemical sensing and actuation properties of polypyrrole coated fibers

Designing complex electrochemical artificial muscles aims towards novel devices which besides excellent actuation capabilities should also present the ability to self-sense the modification of environmental parameters. In order to improve efficiency, mimicking the structure of natural muscles, synthetic actuators should have a similar fibrillary morphology. The importance of using materials based on fiber building blocks in actuators aimed at soft robotics field was demonstrated in the present report by comparing a fibrillary artificial muscle with one based on a classical film structure. Nylon electrospun fiber meshes and films were covered in the same conditions with a thin polypyrrole (PPy) layer. The fibrillary electrospun web morphology mimics that of natural muscles and the structure performs a fast, ample bending movement in liquid electrolyte when switching an applied electric potential between −0.6 and +0.6 V. Using the same actuation conditions, no movement of a film based artificial muscle was observed. In order to check the sensing ability of both fibrillary and film like electroactive architectures, their response i.e. PPy reaction when potential cycles were applied in different concentrations of LiClO4 electrolyte were recorded. The obtained results suggest that the ion exchange of the fibrillary artificial muscle is more efficient due to its higher active surface and such devices could work also as dual device (sensor/artificial muscle).

Poly[vinylidene difluoride] [PVDF] Nanofibrous Web-Based Piezoelectric Material: A Futuristic Solution for Flexible Piezoelectric Energy Harvester

Abstract: Piezoelectric materials are gradually becoming attractive materials for research as far as energy harvesting technologies are concerned. The piezoelectric effect is a pressure-driven phenom-enon that is exhibited by various kinds of crystals, ceramics, polymers, and composites. However, polymers are preferred in piezoelectric applications owing to their flexibility and lightweight. They can easily be incorporated into electronic wearables that cover the demand for flexibility which is one of the most important requirements to improve technology. In this regard, the piezoelectric polymers are found as suitable candidates for energy harvesting. The present review provides a conclusive outlook of polymer-based piezoelectric materials in terms of doping of different fillers in different piezoelectric polymers with a special focus on polyvinylidene fluoride [PVDF] polymer to develop flexible energy harvesters. Moreover, the electrospinning process, a composite fabrication technique has been discussed to cover all the aspects of processing and optimization. Based on significant en-ergy storage capacity PVDF-based flexible electrospun web could be effectively used in day-to-day life.

Enhanced piezoelectric performance of electrospun PVDF nanofibers by regulating the solvent systems

In recreant years, the attention of researchers has been focused on enhancing the electrical outputs of energy harvesting devices. This study reports the generation and characterization of electrospun polyvinylidene fluoride (PVDF) nanofiber webs obtained from different solvents (Acetone (ACE), ACE: N, N-dimethylformamide (DMF) /3:1, ACE: DMF/1:1, ACE: DMF/1:3, and DMF). These electrospun webs will be used as active layers for piezoelectric nanogenerator (PENG). We found that fibers electrospun using DMF have the highest phase content (F(β)), while fibers electrospun using ACE have the lowest one. Furthermore, the results show that PENG based on fiber web electrospun using DMF has the highest electrical outputs, whereas, the lowest electrical outputs were for PENG based on fiber web electrospun using ACE. We believe this work can serve as a good reference for investigating the effect of solvent systems on diameters of fibers, crystalline phases, and piezoelectric properties.

Feasibility study on the application of electrospun nanofiber webs for the air sampling of crystalline silica.

The aim of the present study was to first fabricate an electrospun PVC nanofiber web and then assess its applicability in sampling and measuring the concentration of airborne crystalline silica by comparing analysis results with a commercial PVC membrane filter under different ranges of airborne silica concentration. A filtration performance comparison was also made between an electrospun PVC web with nano-sized fibers and a commercial PVC membrane filter. Overall, the measured concentration of silica by the electrospun webs was 1.022 times higher than that of the commercial PVC filter in all studied ranges of silica concentration and the nanofiber media had higher filtration efficiency and lower pressure drop compared to the PVC membrane filter. This can be considered to be due to the lower fiber diameter and greater porosity (obtained from the 2D SEM image) of the electrospun nanofiber webs. This makes them suited for air pollutant sampling and determining its airborne concentration.

Fabrication of biodegradable polyurethane electrospun webs of fibers modified with biocompatible graphene oxide nanofiller

A successful optimization of the electrospinning parameters for obtainment of biodegradable polyester urethane (DP) webs of fibers, neat and graphene oxide (GO) modified, was performed. The effect of the processing parameters (distance between the needle tip and the collector, applied voltage, and flowing rate), solution type and polymer concentration, on the fiber-forming process and the obtained fibers’ morphology was examined. The best homogeneity of the fibers was achieved for 12 wt% DP dissolved in 80:20 wt% mixture of chloroform and ethanol, applying similar processing parameters for the neat and modified samples (0.5 ml/h pumping rate, 15 kV applied voltage, and 150 mm distance to the collector, for the neat sample, and 0.4 ml/h, 18 kV, and 110 mm, for the GO modified samples). The main novelty of this work is the modification of DP with low quantities (0.5, 1.0 and 2.0 wt%) of GO – the “next generation” nanomaterial for stem cell control. The morphological characterization revealed a fibrous microstructure consisting of randomly oriented fibers with a diameters ranging from hundreds nanometers to couple micrometers, representing a feasible imitation of the structure of extracellular matrix (ECM). The XRD studies showed high dispersion of GO in DP matrix and even exfoliation for the sample that contains 2 wt% GO. Raman studies neatly complemented the highest filler/matrix interactions and the superior levels of dispersion for this sample. TGA was used to analyze the thermo-oxidative degradation and also to determine the actual content of GO present in the samples.

The determinant role of fabrication technique in final characteristics of scaffolds for tissue engineering applications: A focus on silk fibroin-based scaffolds

3D scaffolds are in the center of attention for tissue engineering applications. Whilst many studies have focused on the biological properties of scaffolds, less attention has been paid to meeting the biomechanics of the target tissues. In this work, we show how using the same original biomaterial, but different fabrication techniques can lead to a broad range of structural, mechanical, and biological characteristics. Starting with silk fibroin filament as our base biomaterial, we employed electrospinning, film casting, and weft knitting as different scaffold fabrication techniques. Among these three, the weft knit scaffold showed outstanding cell-scaffold interaction including full 3D cell attachment, complete cell coverage around individual filaments, and in-depth cell infiltration. Post-fabrication degumming of silk filament yarns resulted in more bulky and less open pores for the silk fibroin knit scaffold. The decreased pore size after degumming of knit scaffold alleviated the need to in-advance pore filling (a requisite for increasing cell adhesion in a typical knit scaffold having big pores). From a mechanical viewpoint, the weft knit scaffold shows the highest mechanical strength alongside with far better extensibility. Interestingly, the silk filament weft knit scaffold (in the course direction) was 100 and 1000 times more compliant than silk fibroin film and electrospun web, respectively. The observed effect of material type and fabrication technique highlights the suitability of silk fibroin weft-knit scaffolds for the regeneration of load-bearing soft tissues such as urine bladder.

Bacteria Adhesion of Textiles Influenced by Wettability and Pore Characteristics of Fibrous Substrates.

Bacteria adhesion on the surface is an initial step to create biofouling, which may lead to a severe infection of living organisms and humans. This study is concerned with investigating the textile properties including wettability, porosity, total pore volume, and pore size in association with bacteria adhesion. As model bacteria, Gram-negative, rod-shaped Escherichia coli and the Gram-positive, spherical-shaped Staphylococcus aureus were used to analyze the adhesion tendency. Electrospun webs made from polystyrene and poly(lactic acid) were used as substrates, with modification of wettability by the plasma process using either O2 or C4F8 gas. The pore and morphological characteristics of fibrous webs were analyzed by the capillary flow porometer and scanning electron microscopy. The substrate’s wettability appeared to be the primary factor influencing the cell adhesion, where the hydrophilic surface resulted in considerably higher adhesion. The pore volume and the pore size, rather than the porosity itself, were other important factors affecting the bacteria adherence and retention. In addition, the compact spatial distribution of fibers limited the cell intrusion into the pores, reducing the total amount of adherence. Thus, superhydrophobic textiles with the reduced total pore volume and smaller pore size would circumvent the adhesion. The findings of this study provide informative discussion on the characteristics of fibrous webs affecting the bacteria adhesion, which can be used as a fundamental design guide of anti-biofouling textiles.

Prediction of electrospun web maximum pore diameter reliability

Porosity of electrospun web could be evaluated by the diameter of the maximum pore and the reliability of this value. The distributions of the maximum pore diameter usually differ from Gausian normal distribution, and due to that the standard reliability cannot be used for maximum pore size prediction. The method of electrospun web porosity evaluation by the maximum pore size in the Web is presented in this paper. The main investigations were done with polyamide 6 electrospun nanofibrous web. It was stated that in order to estimate the maximum pore size with a confidence level of 99.5%, it is not possible to use the standard 3S (3 standard deviations) rule in all cases. For reliability prediction, it is possible to use skewness coefficient A or a relative distance between the maximum pore diameter and average value Δd. When skewness coefficient A is up to 1.5 or Δd up to 120% the 4S rule needs to be used instead 3S rule for the same 99.5% reliability prediction.

Water-Resistant Mechanoluminescent Electrospun Fabrics with Protected Sensitivity in Wet Condition via Plasma-Enhanced Chemical Vapor Deposition Process.

Mechanoluminescence (ML), which emits light upon external mechanical stress, was applied to fibrous composites. Herein, ML particles were incorporated into poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) electrospun webs to prepare ML/PVDF and ML/PAN composite fabrics. The produced fabrics were treated with O2 and C4F8 plasma to modify the wetting properties, then the effects of composite wettability on the light-emitting response in dry and wet conditions were investigated. The light intensity was greatly decreased when the composite fabrics absorbed water. When the composites were hydrophobized by the C4F8 plasma-enhanced chemical vapor deposition process, the original light intensity was protected in wet conditions, while maintaining the water vapor transmission rate. As the clothing material would be exposed to moisture in varied situations, the reduced ML sensitivity in wet conditions may limit the application of ML composite fabrics. The findings suggest a facile strategy to fabricate moisture-resistant, breathable mechanoluminescence composite fabrics.

Electrospun ion gel nanofibers for high-performance electrochromic devices with outstanding electrochromic switching and long-term stability

Here we present the enhanced electrochemical properties of ion gel nanofiber-based electrochromic devices (ECDs) prepared by electrospinning. The ECDs were fabricated by sandwiching prepared electrospun nanofiber webs between two transparent electrodes. The electrochromic behaviors of the ECDs were investigated using cyclic voltammetry, spectroelectrochemistry, and kinetic stability measurements. In order to determine the origin of the enhanced EC behaviors, the morphological structures of the nanofiber were examined by a scanning electron microscope, which showed that an ionic liquid (IL) region enclosed the pores between the nanofibers in the solid phase. The increased IL contents in the interstices of the nanofibers were noted, which would induce higher ionic mobility. Consequently, the fabricated nanofiber-based ECDs showed greatly enhanced device performance in terms of switching speed, cyclic stability, and coloration efficiency. Furthermore, flexible ECDs were fabricated by sandwiching the electrospun webs between two plastic electrodes consisting of silver nanowire/PEDOT:PSS hybrid electrodes. The fabricated device revealed a color switching over the large active area, with the transmittance changes maintained over repeated bending cycles. These nanofiber-based ECDs are evidence of a practical approach by which to realize large-area electrochromic devices with excellent chromatic switching and long-term cyclic stability, suitable both for rigid and flexible devices.

Structure and performance analysis of flatter ribbon-like electrospun poly(L-lactic acid)/graphene oxide nanofiber webs

Polylactic acid matrix composites are widely used in packagings and biomaterials. The specific surface area, flexibility and degradation efficiency of the material are the key factors to determine its application in these fields. In this study, a series of poly(L-lactic acid) (PLLA)/graphene oxide (GO) composite nanofiber webs were prepared using electrospinning technique. The scanning electron microscope (SEM) image of PLLA/GO nanofibers showed a rougher surface and a smaller average diameter compared with that of pure PLLA nanofibers, and the nanofibers with 6 wt% GO in PLLA matrix looked like flatter ribbon. Accordingly, the tensile stress test of the electrospun webs with different GO contents showed high performance, 400% increment in the tensile stress at presence of 6 wt% GO. The hydrolytic degradation behavior of composite the nanofiber webs exhibited that the presence of GOs greatly improved the degradation rate, after 9 days, the degradation ratio of PLLA/GO can reach 16.83%. of the PLLA matrix, resulting from the better hydrophilic property and absorbability. Using GO to improve the preparation of new biocompatible materials from PLLA can provide a reference for problems in the field of packaging materials.

Measurement of Adhesion of In Situ Electrospun Nanofibers on Different Substrates by a Direct Pulling Method

In some cases, we hope to remove the electrospun nanofibrous mesh from the collector easily. But in some cases such as wound dressing, we observe that the in situ electrospun nanofibers can stick to the collector (e.g., skin). Therefore, the adhesion between the in situ electrospun web and the substrate becomes important in the performance and practical application of the electrospun material. In this paper, we reported a direct pulling method to measure the adhesion and understand the adhesion mechanism. In this method, we used gravity to pull the fiber directly from the substrate and then measured the gravity to calculate the adhesion. This new test method is more convenient and practical than the previously reported methods. In addition, the adhesion of the in situ electrospun web on different substrates (e.g., aluminium foil, wood pulp paper, and silicon paper) was also studied by this method. The adhesion was influenced by spinning voltage, electrical conductivity, and surface roughness of the substrates.

Investigation of Lactobacillus paracasei encapsulation in electrospun fibers of Eudragit® L100

Abstract Some species of Lactobacillus have demonstrated beneficial health effects being applied in the production of food supplements. Thus, the incorporation of viable cells as encapsulated probiotics represents an essential condition to be considered in new strategies for the controlled release of microorganisms. Herein, the massive encapsulation of Lactobacillus paracasei is provided by the use of alternative electrospinning technique. Is spite of the high voltage required for the production of fibers, a high density of viable cells is observed into the polymeric electrospun web, allowing the controlled release at targeted pH (characteristic of Eudragit® L100 polymer support). The reported procedure circumvents typical drawbacks of degradation of microorganisms under adverse conditions (storage, package and low pH) and preserves its biologic action after complete release from polymer fibers.

Facile Functionalization via Plasma-Enhanced Chemical Vapor Deposition for the Effective Filtration of Oily Aerosol.

With the growing concern about the health impacts associated with airborne particles, there is a pressing need to design an effective filter device. The objective of this study is to investigate the effect of plasma-based surface modifications on static charges of electrospun filter media and their resulting filtration performance. Polystyrene (PS) electrospun web (ES) had inherent static charges of ~3.7 kV due to its electric field-driven process, displaying effective filtration performance. When oxygen species were created on the surface by the oxygen plasma process, static charges of electret media decreased, deteriorating the filter performance. When the web surface was fluorinated by the plasma-enhanced chemical vapor deposition (PECVD), the filtration efficiency against oily aerosol significantly increased due to the combined effect of decreased wettability and strong static charges (~−3.9 kV). Solid particles on the charged media formed dendrites as particles were attracted to other layers of particles, building up a pressure drop. The PECVD process is suggested as a facile functionalization method for effective filter design, particularly for capturing oily aerosol.