Electrospun Fiber Mats Research Articles

Control of mat thickness in electrospinning with transparent conductive glass collector

AbstractElectrospinning is a versatile technique for producing micro‐ and nanofibrous mats with great potential in many fields. However, reproducibility remains a key issue for product development. In particular, thickness is an important parameter for controlling electrospun fiber mats. In this study, we developed a method to control the polymer mat thickness during electrospinning. The mat thickness was controlled on the basis of the light transmittance and by using conductive indium tin oxide (ITO) glass connected to ground as a collector. Living cells were seeded on the fiber mat without detaching from the ITO glass, which enabled observation under a microscope and the evaluation of cell behavior. This study indicates that the thickness of the fiber mat can be consistently controlled by monitoring the light transmittance instead of the electrospinning duration and the mat can be easily observed under a microscope. This is expected to be particularly useful in the field of tissue engineering.

A comprehensive review on electrospun nanohybrid membranes for wastewater treatment.

Electrospinning, being a versatile and straightforward method to produce nanofiber membranes, has shown significant advancement in recent years. On account of the unique properties such as high surface area, high porosity, mechanical strength, and controllable surface morphologies, electrospun nanofiber membranes have been found to have a great potential in many disciplines. Pure electrospun fiber mats modified with different techniques of surface modification and additive incorporation have exhibited enhanced properties compared to traditional membranes and are even better than the as-prepared electrospun membranes. In this review, we have summarized recently developed electrospun nanohybrids fabricated by the incorporation of functional specific nanosized additives to be used in various water remediation membrane techniques. The adsorption, filtration, photocatalytic, and bactericidal capabilities of the hybrid membranes in removing common major water pollutants such as metal ions, dyes, oils, and biological pollutants have been discussed. Finally, an outlook on the future research pathways to fill the gaps existing in water remediation have been suggested.

Piezoelectric biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) based electrospun fiber mats with tailored porosity

AbstractPiezoelectric polymers allow transducing a mechanical stimulus into an electrical voltage, and vice‐versa, leading to a large variety of sensor and actuator applications. Further, biodegradable platforms are increasingly needed in the environmental and biotechnological areas. In this context, this work reports on electrospun fiber based membranes with tailored physical properties and morphology, through the combination of the piezoelectric and biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) polymer with poly(ethylene oxide). The use of a binary polymer mixture and a binary solvent system of chloroform and dimethylformamide allows these materials to have their external and internal morphologies tailored. The porosity of the neat and blend fibers ranges between 79% and 93%. The produced materials demonstrated huge potential for environmental and biotechnological applications that require piezoelectricity, biodegradability, and porosity.

Preparation of Novel partially Bio-Based Thermoplastic Polyurethane / Polyacrylonitrile Electrospun Fiber Mats

The partially bio-based thermoplastic polyurethane/polyacrylonitrile electrospun fiber mats at various weight ratio was fabricated via electrospinning technique. A partially bio-based thermoplastic polyurethane was prepared from caprolactone diol and partially bio-based diisocyanate at a mole ratio of 2.1:1. Ethylene glycol was used as a chain extender. Three major effects i.e. solution concentration, distance from tip to collector and applied voltage on morphology of the obtained electrospun fiber mats were systematically investigated using a scanning electron microscope. The design of experiment, namely, Taguchi method was also applied. The morphology of the prepared electrospun fiber mats revealed continuous and smooth fibers without the formation of beads. The fiber diameters of the thermoplastic bio-based polyurethane/polyacrylonitrile were in micron size ranging from 0.2 to 1.4 μm. Moreover, the results showed that with the decrease of concentration, the fiber diameter decreased where the changes of applied voltage and distance from tip to collector resulted in negligible changes in fiber diameter. The findings can be further applied as processing conditions to meet properties requirements for the high-performance separator application.

In situ synthesized amphiphilic polysulfone‐poly(ethylene‐glycol) block copolymer/silver nanocomposite for separating oil/water emulsion

AbstractThis work reports the synthesis of silver nanoparticles from the precursors, silver nitrate and sodium bromide, and the in situ synthesis of polysulfone (PSf)‐poly(ethylene‐glycol) (PEG) block copolymer (BCP) in the presence of developed Ag. The PSf‐PEG BCP nanocomposite containing 3 wt.% of the nanoparticles, when electrospun, is observed to be helpful in separating the oil‐in‐water emulsion. Mechanical properties such as dynamic mechanical strength and tensile strength measurements and high thermal degradation temperature (~6°C) illustrate the reinforcing effect of the Ag nanoparticles. The presence of Ag influences the glass transition temperature (Tg) of the BCP and its elasticity due to its well distribution in the BCP during the in situ synthesis of nanocomposite. Electrospun fiber mat of the in situ synthesized PSf‐PEG/Ag nanocomposite shows improved wettability as evident from the respective aqueous contact angle values of 80.66° ± 1.3, 85.70° ± 2.0, and 101.50° ± 1.0 for PSf‐PEG/Ag, PSf‐PEG, and neat PSf. The combination of PEG to PSf has increased the overall polymer reinforcement effect, and this property along with the antimicrobial activity (inhibited growth of Staphylococcus aureus) of Ag nanoparticles are applied in developing bio‐fouling resistant BCP nanocomposite fibers for oil/water emulsion separation.

Enhanced piezoelectric performance of aligned PVDF electrospun fiber mats

Enhanced piezoelectric performance of aligned PVDF electrospun fiber mats

Electroactive poly(vinylidene fluoride) electrospun fiber mats coated with polyaniline and polypyrrole for tissue regeneration applications

Electrospun membranes with an active response are playing an increasing role in tissue regeneration by improving the ability of the materials to mimic the cellular microenvironment during cell culture. In this context, this work reports on the development of poly(vinylidene fluoride) (PVDF) electrospun fibers coated with polyaniline (PANI) and with polypyrrole (PPy). Both PANI and PPy successfully coated the fibers, with the surface electrical conductivity of the coatings reaching values of σ = 1.19 S.m−1 for PVDF-PPy and σ = 3.84 × 10−3 S.m−1 for PVDF-PANI. Furthermore, the PVDF samples became hydrophilic upon their coating with either PANI or PPy, the fiber mats adsorbing the water drop after a few seconds. The coated samples remain biocompatible, resulting in a slight improvement in the metabolic activity of L929 fibroblasts.

Flow-induced bending deformation of electrospun polymeric filtration membranes using the “leaky” bulge test

In service, hydraulic flow is usually perpendicular to the plane of electrospun fiber mats for water filtration, inducing an out-of-plane deformation. In this paper, we have investigated the out-of-plane deformation response of wet electrospun polyacrylonitrile fiber mats with distinct average constituent fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm, but with nominally similar thicknesses and areal densities using the classical bulge testing technique. The resultant pressure-deflection relationships are incompatible with constitutive models for out-of-plane deformation of continuum materials. Rather, the fiber mats exhibited a one-half dependence (p∼h12) governed by fiber deflection, and pressure asymptote indicative of steady-state fluid percolation, but influenced by the mats areal densities. In addition, the apparent bending rigidity increased with increasing fiber diameter. In the range tested for fiber mats with average fiber size of 232 nm, increase in mat thickness did not noticeably alter measured rigidities, although evidence of slight increase in pressure asymptote is observed. Cyclic flow rate tests provided evidence of good recoverability as well as minimal topological modifications.

Alkali Ions Transport into Lignin-Based Hard Carbon Fibers

Hard carbons are considered as preferred negative electrodes in the development of sodium- and potassium-ion batteries because of low working potential, high capacity, as well as good cycling stability. A further advantage is that they can be made from renewable precursors, in this case lignin. The structure changes of the precursors during synthesis of the hard carbons have been extensively studied1–3. The alkali ions insertion mechanism broadly accepted by the community is the insertion into the carbonaceous structure in the slope region, and a pore filling mechanism in the plateau region of the galvanostatic profile. The diffusion of sodium ions and potassium ions into hard carbon electrodes has been investigated using Galvanostatic Intermittent Titration Technique (GITT) combined with analytical models4,5. However, a physics-based model can be used instead in order to analyze the experimental data and investigate potassium- and sodium ion transport into hard carbon electrodes in greater details.In this work a physics-based single particle model combined with GITT experimental data has been used to investigate the effects of carbonization temperature and state of charge on potassium ions diffusion into an electrode made from pure lignin based hard carbon fibers. Electrospun fiber mat electrodes carbonized in the temperature range from 800 °C to 1700 °C have been investigated. The parameters extracted from the physics-based model have been used to shed further light on the insertion mechanism. Finally, the study was extended to sodium ions to investigate the impact of various alkali ions.The results show that diffusion coefficients as well as electrochemical rate constants depend of carbonization temperature and state of charge. The physics-based model cannot reproduce the experimental data well by only considering diffusion, and a second time constant needs to be considered in the model. The coupling of parameters and open circuit voltage (OCV) curves extracted from the GITT experimental data supports that the slope region refers to the insertion into the carbonaceous structure and the plateau region refers to the pore filling mechanism. References Morikawa, Y., Nishimura, S., Hashimoto, R., Ohnuma, M. & Yamada, A. Mechanism of Sodium Storage in Hard Carbon: An X‐Ray Scattering Analysis. Adv. Energy Mater. 10, 1903176 (2020).Kubota, K. et al. Structural Analysis of Sucrose-Derived Hard Carbon and Correlation with the Electrochemical Properties for Lithium , Sodium , and Potassium Insertion Structural Analysis of Sucrose-Derived Hard Carbon and Correlation with the Electrochemical Properties fo. (2020) doi:10.1021/acs.chemmater.9b05235.Buiel, E. R., George, A. E. & Dahn, J. R. Model of micropore closure in hard carbon prepared from sucrose. Carbon N. Y. 37, 1399–1407 (1999).Jian, Z., Xing, Z., Bommier, C., Li, Z. & Ji, X. Hard Carbon Microspheres: Potassium-Ion Anode Versus Sodium-Ion Anode. Adv. Energy Mater. 6, 1501874 (2016).Li, Y., Hu, Y. S., Titirici, M. M., Chen, L. & Huang, X. Hard Carbon Microtubes Made from Renewable Cotton as High-Performance Anode Material for Sodium-Ion Batteries. Adv. Energy Mater. 6, 1–9 (2016). Figure 1

Polyisobutylene-New Opportunities for Medical Applications.

This paper presents the results of the first part of testing a novel electrospun fiber mat based on a unique macromolecule: polyisobutylene (PIB). A PIB-based compound containing zinc oxide (ZnO) was electrospun into self-supporting mats of 203.75 and 295.5 g/m2 that were investigated using a variety of techniques. The results show that the hydrophobic mats are not cytotoxic, resist fibroblast cell adhesion and biofilm formation and are comfortable and easy to breathe through for use as a mask. The mats show great promise for personal protective equipment and other applications.

Combining Electrospinning and Electrode Printing for the Fabrication of Stretchable Organic Electrochemical Transistors

Stretchable conductors and organic electrochemical transistors (OECT) were fabricated from PEDOT:Tos (poly (3,4-ethylenedioxythiophene):iron tosylate) nanofibers. The devices were prepared by a combination of electrospinning and electrode printing followed by vapor phase polymerization (VPP). The impact of both the processing time and the composition of three electrospinning mixtures on the electrospun fiber mats was evaluated by scanning electron microscopy and cyclic voltammetry. Fibrillar mats prepared from the different mixtures maintained their electrical properties and could be stretched up to 140% of their original length. Stretchable OECTs were fabricated by printing silver drain and source electrodes directly on the conductive spun fibers. The fabricated devices showed transistor behavior up to ∼50% strain.

Electrospun fiber mats with multistep seeded growth of UTSA-16 metal organic frameworks by microwave reaction with excellent CO2 capture performance

A novel flexible PAN fiber adsorbent was developed using an electrospinning technique with UTSA-16 (Co) and UTSA-16 (Zn) metal organic frameworks (MOFs). MOF powders with different ratios were dispersed within PAN fiber networks and processed to produce MOF crystalline layers under microwave irradiation for the seeded growth of MOFs. The PAN/UTSA-16 (Co) and (Zn) fiber mats exhibit 75% and 78% of the CO 2 adsorption capacities of pristine UTSA-16 (Co) and UTSA-16 (Zn), respectively, while a high CO 2 /N 2 selectivity of 113–128 is preserved. Stability experiments show that PAN/UTSA-16 (Zn) fibers are more robust under humid air, NO 2 , and SO 2 environments compared to PAN/UTSA-16 (Co). Additionally, the PAN/UTSA-16 fibers show excellent recyclability during ten adsorption-desorption cycles at 298 and 393 K. Morphology, porous properties, and crystallinity of the PAN/UTSA-16 fibers were examined using SEM, BET, and XRD. ● Flexible fiber mats with UTSA-16 (Co) and (Zn) were produced by using an electrospinning and microwave irradiation. ● PAN/UTSA-16 fiber mats show even better CO2 adsorption capacity and selectivity than powder adsorbents. ● Excellent recyclability was proven by a repeated adsorption-desorption at 298 and 393 K. ● Stability of PAN/UTSA-16 fiber mats under humid air, SO 2 , and NO 2 was evaluated for a practical application.

Scaffolds Designing from Protein-loadable Coaxial Electrospun Fibermats of poly(acrylamide)-Co-poly(diacetone acrylamide) and Gelatin

Background: Aiming at in situ regenerative therapy, the tailored design of cytokine-releasing scaffolds is still one of the crucial issues to be studied. A core-shell fibermat is one of the attractive platforms for this purpose. But, very few detail the importance of choosing the right material for the shell units that can endow efficient release properties. Objective: In this study, we characterized the effectiveness of core-shell fibermats that possess cross-linked gelatin (CLG) as the shell layer of constituent nanofibers, as a protein-releasing cell-incubation scaffold. Methods: For the core nanofibers in the core-shell fibermats, we utilized a crosslinked copolymer of poly(acrylamide)-co-poly(diacetone acrylamide) (poly(AM/DAAM)) and adipic acid dihydrazide (ADH), poly(AM/DAAM)/ADH. By coaxial electrospinning and the subsequent crosslinking of the gelatin layer, we successfully constructed core-shell fibermats consisting of double-layered nanofibers of poly(AM/DAAM)/ADH and CLG. Using fluorescein isothiocyanate-labeled lysozyme (FITC-Lys) as a dummy guest protein, we characterized the release behavior of the coreshell fibermats containing a CLG layer. Upon loading basic fibroblast growth factor (bFGF) as cargo in our fibermats, we also characterized impacts of the released bFGF on proliferation of the incubated cells thereon. Results: Although the single-layered poly(AM/DAAM)/ADH nanofiber fibermats did not adhere to the mammalian cells, the core-shell fibermat with the CLG shell layer exhibited good adherence and subsequent proliferation. A sustained release of the preloaded FITC-Lys over 24 days without any burst release was observed, and the cumulative amount of released protein reached over 65% after 24 days. Upon loading bFGF in our fibermats, we succeeded in promoting cell proliferation, and highlighting its potential for use in therapeutic applications. Conclusion: We successfully confirmed that core-shell fibermats with a CLG shell layer around the constituent nanofibers, were effective as protein-releasing cell-incubation scaffolds.

Delivery of Bioactive Gene Particles via Gelatin-Collagen-PEG-Based Electrospun Matrices.

The fabrication of fiber mats via electrospinning has been adopted in the last decades to produce high quality scaffolds for tissue engineering. However, an effective combination of electrospinning methods with gene delivery therapies remains a challenge. In this study, we describe how the delivery of gene complexes via electrospun mats that contain different volumes of gelatin (Gel), collagen (Col), and polyethylene glycol (PEG) can affect gene expression by transfected cells. Non-viral complexes were formulated by using lipid modified polyethylenimine (PEI) polymer and plasmid DNAs (pDNA) like the reporter Green Fluorescent Protein (GFP) and the therapeutically relevant Bone Morphogenetic Protein-2 (BMP-2) and electrospuned after being mixed with different volumes of Gel-Col-PEG mats and delivered to human myoblast (C2C12) and mouse osteoblast cells (MC3T3). The entrapment of GFP complexes via different homogeneous electrospun fiber mats revealed that a high fraction of collagen in the mats affected the quality of the fibers and led to reduced transfection efficiency on target cells. On the other hand, the fabrication of double-layered mats that contained collagen without complexes as a first layer and gelatin-collagen-PEG with complexes as a second layer successfully induced GFP expression and ALP activity in C2C12 cells. We conclude that this study has established the advantage of formulating multilayered bioactive collagen-based mats for gene delivery applications.

Highly Stretchable and Permeable Conductors Based on Shrinkable Electrospun Fiber Mats

Highly Stretchable and Permeable Conductors Based on Shrinkable Electrospun Fiber Mats

Evaluation of the Photocatalytic Activity and Anticorrosion Performance of Electrospun Fibers Doped with Metallic Oxides.

This paper reports the development and characterization of a multifunctional coating that combines anticorrosion and photocatalytic properties, deposited by means of the electrospinning technique. In the first step, a functional electrospun fiber mat composed of poly(acrylic acid) (PAA) and β-cyclodextrin (β-CD) was obtained, showing high water insolubility and great adhesion increased by means of a thermal crosslinking process (denoted as PAA + β-CD). In the second step, the fibers were doped with particles of titanium dioxide (denoted as PAA + β-CD/TiO2) and titanium dioxide plus iron oxide (denoted as PAA + β-CD/TiO2/Fe2O3). The morphology and fiber diameter of the electrospun mats were evaluated by using confocal microscopy, whereas the presence of the metal oxides in the electrospun fibers was corroborated by scanning electron microscopy (SEM) and X-ray fluorescence (XRF), respectively. In addition, electrochemical tests in saline solution revealed that the sample composed of PAA + β-CD/TiO2/Fe2O3 showed the highest corrosion protection efficiency of all the samples, which was directly associated to lower corrosion current density and higher corrosion potential. Furthermore, the paper reports a novel approach to in situ determination of methylene blue (MB) degradation onto the coating. The results revealed complete degradation of MB, which is perfectly appreciated by total discoloration of the film in the irradiated zone (from bluish to a white spot). The main conclusions of this research are the efficiency of the electrospun system PAA + β-CD/TiO2/Fe2O3 for developing photocatalytic activity and corrosion protection and the utility of the dry MB discoloration tests to evaluate photocatalytic activity.

In-situ cellulose-framework templates mediated monodispersed silver nanoparticles via facile UV-light photocatalytic activity for anti-microbial functionalization

Cellulose is well known as a biocompatible material or natural reducing material. In this study, As an eco-friendly and facile method, we prepared monodispersed silver nanoparticles (AgNPs) in cellulose-framework through photocatalytic reaction. and we fabricated electrospun fiber scaffolds with excellent antibacterial properties and biocompatibility. UV-irradiation causes the electrical change of the cellulose-framework, thereby converting Ag ions into Ag particles. We applied a three-electrode system to confirm the phenomenon. Through STEM and EDS, it was found that the synthesized AgNPs were monodisperse in the nanofibers, and antibacterial activity was confirmed using gram-negative and gram-positive bacteria. In addition, it was suggested that the gradual release of simvastatin contained in the nanofibers and excellent mineralization would be easy to apply to bone regeneration. Therefore, the manufactured composite electrospun fiber mat can be used not only in biomedical fields but also in various applications that need to prevent the accumulation of microorganisms.

Investigation of electromechanical properties of as-electrospun polystyrene fiber mat via sequential approaching/loading technique

Electromechanically active submicron/micron polymer fibers are promising building blocks for biological/soft-robotic motion sensors and pressure sensors. In particular, mats of the fibers produced by electrospinning demonstrated distinct direct/converse electromechanical properties compared to those of films. Although several studies have demonstrated the direct electromechanical characteristics of the electromechanically active electrospun fiber mats, detailed investigation of the characteristics when the testing probe starts to contact the fiber mats, in addition to the effect on the preloading value, have not been reported. In this study, a sequential approaching/loading electromechanical testing technique has been proposed for a detailed investigation of the electromechanical properties of the fiber mats, in particular, near the contact between the testing electrode and the fiber mats. The results demonstrate that the preload and load values significantly affect the measured values of the apparent piezoelectric d constant (dapp). Therefore, careful determination of the applied preload and load values was a prerequisite for measuring the dapp of the very soft fiber mats. The present technique also demonstrates that the measured value of the capacitance of the fiber mat is significantly affected by the value of the applied load; therefore, a careful determination of the loading value is indispensable for measuring the capacitance of the fiber mats. The proposed technique can pave the way for a deep understanding of the direct electromechanical characteristics of a variety of significantly soft submicron/micron fiber mats and can aid the exploration of strategies to develop advanced biological/soft-robotic motion sensors and pressure sensors employing these mats.

The effect of electrospun scaffolds on the glycosaminoglycan profile of differentiating neural stem cells

The use of electrospun scaffolds for neural tissue engineering applications allows a closer mimicry of the native tissue extracellular matrix (ECM), important for the transplantation of cells in vivo. Moreover, the role of the electrospun fiber mat topography on neural stem cell (NSC) differentiation remains to be completely understood. In this work REN-VM cells (NSC model) were differentiated on polycaprolactone (PCL) nanofibers, obtained by wet/wet electrospinning, and on flat glass lamellas. The obtained differentiation profile of NSCs was evaluated using immunofluorescence and qPCR analysis. Glycosaminoglycan (GAG) analysis was successfully emplyed to evaluate changes in the GAG profile of differentiating cells through the use of the highly sensitive liquid chromatography-tandem mass/mass spectrometry (LC-MS/MS) method. Our results show that both culture platforms allow the differentiation of REN-VM cells into neural cells (neurons and astrocytes) similarly. Moreover, LC-MS/MS analysis shows changes in the production of GAGs present both in cell cultures and conditioned media samples. In the media, hyaluronic acid (HA) was detected and correlated with cellular activity and the production of a more plastic extracellular matrix. The cell samples evidence changes in chondroitin sulfate (CS4S, CS6S, CS4S6S) and heparan sulfate (HS6S, HS0S), similar to those previously described in vivo studies and possibly associated with the creation of complex structures, such as perineural networks. The GAG profile of differentiating REN-VM cells on electrospun scaffolds was analyzed for the first time. Our results highlight the advantage of using platforms obtain more reliable and robust neural tissue-engineered transplants.

The effect of deposition angle on morphology and diameter of electrospun TiO2/PVP nanofibers

Electrospinning has become a robust technique for the cost-effective production of fibrous materials. In a conventional electrospinning process, the produced fibers are fabricated by either vertical or horizontal setups, resulting in isotropic non-woven fibers mats. Many researchers have focused on the influence of various electrospinning parameters, solution parameters and ambient parameters. However, until now less attention has been paid on the impact of gravity on fiber and mat morphologies. This article presents a novel approach for altering the morphology of electrospun TiO2/PVP nanofiber mats using a simple concept based on different deposition angles. The electrospinning setups used involved five deposition angles (0°, 45°, 90°, 135°, and 180°), which revealed an effect of gravity on fiber mat morphology and fiber diameter. This work provides new prospects toward the design of electrospun fiber mats and provides us with additional options to achieve optimal results.