Submicron Fibers Research Articles

Morphology and conductivity of polyaniline sub-micron fibers prepared by electrospinning

Sub-micron fibers of pure polyaniline (PANI) doped with sulfuric acid or hydrochloric acid were prepared by electrospinning PANI with suitable molecular weight dissolved in hot sulfuric acid. A modified electrospinning setup was employed with a coagulation bath as a collector, where dilute sulfuric acid was used as coagulation bath. The factors influencing the morphology and conductivity of the synthesized PANI fibers were investigated, including the concentration of dilute H 2SO 4 solution in the coagulation bath, the doped PANI concentration in H 2SO 4 solution, the type of doping acid and the voltage applied to the solution. The morphologies of doped PANI fibers were characterized by scanning electron microscope (SEM). The structure of the resulting fibers was analyzed by Fourier transform infrared spectroscopy and UV–vis spectrometer. The conductivity of PANI fibers were characterized by I– V characteristics. Homogeneous PANI fibers with a diameter of 370 nm and a high conductivity of 52.9 S/cm were prepared. The possible mechanisms of different morphology formation and conductivity of PANI fibers were also discussed.

Nanofiber-based scaffolds for tissue engineering

For successful tissue engineering, it is essential to have as many biomimetic scaffolds as possible. With increasing interest in nanotechnology, development of nanofibers (n-fibers) by using the technique of electrospinning is having a new momentum. Among important potential applications of n-fiber-based scaffolds for tissue engineering represent an important advancing front. Nanoscaffolds (n-scaffolds) mimic natural extracellular matrix (ECM) and its nanoscale fibrous structure. With electrospinning, it is possible to develop submicron fibers from biodegradable polymers and these can also be used for developing multifunctional drug-releasing and bioactive scaffolds. Developed n-scaffolds are tested for their cytocompatibility using various cell models. In addition, they were seeded with cells for engineering tissue constructs. There is a large area ahead for further applications and development of these scaffolds. For instance, multifunctional scaffolds that can be used as controlled delivery system do have a potential and have yet to be investigated for improved engineering of various tissues. So far, there are only very few in vivo studies on n-scaffolds, but in the future many are expected to emerge. With the convergence of the fields of nanotechnology, drug release, and tissue engineering, new solutions could be found for the current limitations of tissue engineering. In this paper, nanoscaffolds developed by using electrospinning, used polymers so far, cytocompatibility and applications in tissue engineering are reviewed.

Electrospun cellulose acetate fibers containing chlorhexidine as a bactericide

Submicron fibers with bactericidal properties were prepared from electrospinning of blends containing cellulose acetate (CA) as a polymer base, chlorhexidine (CHX) as a bactericidal agent, and organic titanate Tyzor® TE (TTE) as a cross-linker. A small amount of high molecular weight poly(ethylene oxide) (PEO) was incorporated into the blends to facilitate the electrospinning, and its effect on the extensional properties and spinnability of the N,N-dimethylformamide (DMF) solutions were evaluated. The CHX-containing fiber meshes were cured by TTE in the presence of water vapor, which created covalent links between the CA and CHX. The immobilization of CHX on or within the fibers was confirmed by FTIR, Raman and XPS measurements. The resulting fiber meshes exhibited bactericidal properties on contact, due to the CHX immobilized on the fibers, and within a zone of inhibition (ZoI), due to the release of unbound CHX. The relationship of ZoI for the gram-negative Escherichia coli and the gram-positive Staphylococcus epidermidis to the amount of unbound CHX in the fibers is described by a simple diffusion model. The contact bactericidal capacity against both E. coli and S. epidermidis was assayed after complete removal of unbound CHX from the fibers. A post-spin treatment to attach CHX onto CA–PEO fibers via TTE linkers was also shown to be effective.

Creating small diameter bioresorbable vascular grafts through electrospinning

Seamless, non-woven, bioresorbable vascular prosthetics composed of sub-micron fibers have been successfully created through electrospinning. These prosthetics have proven to be both bioactive and mechanically viable during in vitro testing, and hold great potential to be conducive to in situ tissue engineering/regeneration in the future.

Self-organized submicron fibers in single crystal from high temperature elaboration

We describe a high temperature route elaboration process of metamaterials: monocrystals of Cu(Ge,Si)O 3 with SiO 2–GeO 2 glass fibers embedded in it. It is a novel type of two-phase material obtained starting from a mixture of oxides carried to fusion in a floating zone furnace and solidified in a preferred direction. The synthesized material exhibits nearly periodic fiber structures for a range of parameter set. This method opens up the possibility to produce photonic crystals at low cost and in great quantities.

Composite Membranes for Hydrogen/Air PEM Fuel Cells

Composite membranes containing sub-micron diameter electrospun fibers of proton conducting sulfonated poly(ether ether ketone) have been fabricated. Interconnected fibers were formed into a dense mat and then embedded with an inert polymer matrix to create a water/gas impermeable proton conducting fuel cell membrane. The fibers were composed of 1.65 mmol/g ion-exchange capacity polymer and the inert matrix polymer was a commercially available photocrosslinkable and solvent-less adhesive, NOA 63 (Norland Optical Adhesive). After electrospinning and before NOA embedding, the fiber mat was densified by heating and the fibers were welded to one another by exposure to ethanol solvent. The volume fraction of fibers in the resulting membranes was high (0.74) and the proton conductivity after embedding NOA 63 was 0.049 S/cm (for water equilibration at 25oC).

Fabrication and characterization of a boehmite nanoparticle impregnated electrospun fiber membrane for removal of metal ions

The fabrication of a composite electrospun fiber membrane with sorptive characteristics intended for removal of heavy metals was investigated. The electrospun fiber membrane was impregnated with nano-boehmite particles. The latter had been selected to increase surface area of the active component. Cd (II) was chosen as the challenge bivalent cation. The sorption capacity of the nano-boehmite was studied as a function of pH and time. Electrospinning was used to prepare the composite submicron fiber membrane impregnated with boehmite nanoparticles. The later was blended with the polymer to produce a homogenous mixture before electrospinning. Two polymers, the hydrophobic/PCL/and hydrophilic/Nylon-6/, were chosen to serve as the support for the boehmite. The nanoparticles and resulting composite membranes were characterized using SEM, TEM, and XRD techniques. XRD data confirmed the presence of nano-boehmite particles in the nanofibers membrane. The membranes so prepared were challenged with aqueous solutions of Cd in batch isotherm tests. Atomic absorption spectroscopy results show sorption of Cd (II) by boehmite impregnated electospun membrane was possible and a capacity of 0.20 mg/g was achieved.

Interior structure of polyacrylonitrile(PAN) nanofibers with LiCl

Electrospinning is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. In this work, the interior structure of electrospinning PAN nanofibers by adding different content of LiCl is investigated. The diameter of nanofibers, electrospun by solutions with different content of LiCl reduces in the following order: 1 wt.%LiCl>2 wt.%LiCl>3 wt.%LiCl>4 wt.%LiCl. The X-ray diffraction patterns of electrospinning nanofibers with or without LiCl do not change much. The crystallinity of nanofibers with LiCl is generally lower than that of nanofibers without LiCl. Moreover, the added salts are propitious to electrospinning and the chemical composition of PAN is also found to be unchanged.

Preparation of water-stable submicron fibers from aqueous latex dispersion of water-insoluble polymers by electrospinning

Submicron polystyrene (PS) fibers were prepared by electrospinning of an aqueous dispersion of PS latex and a small amount of poly(vinyl alcohol) (PVA) and subsequent extraction by water. Depending on particle size, surfactant, ratio of PS:PVA, and applied voltage fibers of different morphology and water stability were obtained. Analysis of latex fibers by TEM revealed hexagonal packaging of particles within the fibers.

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

Abstract The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 105 and 1.80 × 106 g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.

Phase-matched third-harmonic UV generation using low-order modes in a glass micro-fiber

We observe phase-matched third-harmonic generation at 355 nm in a low-order mode of a sub-micron diameter glass fiber. The third-harmonic signal exhibits a sharp resonance for a fiber diameter d = 0.49 ± 0.02 μm, in excellent agreement with the value d = 0.506 μm predicted by theory. The third-harmonic conversion efficiency is 2 × 10 −6, and is limited by the pump power (1 kW) and effective fiber length (100 μm).

Biodegradable Nanomats Produced by Electrospinning: Expanding Multifunctionality and Potential for Tissue Engineering

With increasing interest in nanotechnology, development of nanofibers (n-fibers) by using the technique of electrospinning is gaining new momentum. Among important potential applications of n-fiber-based structures, scaffolds for tissue-engineering represent an advancing front. Nanoscaffolds (n-scaffolds) are closer to natural extracellular matrix (ECM) and its nanoscale fibrous structure. Although the technique of electrospinning is relatively old, various improvements have been made in the last decades to explore the spinning of submicron fibers from biodegradable polymers and to develop also multifunctional drug-releasing and bioactive scaffolds. Various factors can affect the properties of resulting nanostructures that can be classified into three main categories, namely: (1) Substrate related, (2) Apparatus related, and (3) Environment related factors. Developed n-scaffolds were tested for their cytocompatibility using different cell models and were seeded with cells for to develop tissue engineering constructs. Most importantly, studies have looked at the potential of using n-scaffolds for the development of blood vessels. There is a large area ahead for further applications and development of the field. For instance, multifunctional scaffolds that can be used as controlled delivery system do have a potential and have yet to be investigated for engineering of various tissues. So far, in vivo data on n-scaffolds are scarce, but in future reports are expected to emerge. With the convergence of the fields of nanotechnology, drug release and tissue engineering, new solutions could be found for the current limitations of tissue engineering scaffolds, which may enhance their functionality upon in vivo implantation. In this paper electrospinning process, factors affecting it, used polymers, developed n-scaffolds and their characterization are reviewed with focus on application in tissue engineering.

Effect of different salts on electrospinning of polyacrylonitrile (PAN) polymer solution

AbstractElectrospinning is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. If the solution is absolutely insulating, or the applied voltage is not high enough that electrostatic force cannot overcome the surface tension, then no fiber can be produced by electrospinning; however, if some salt is added in the solution, the problem can be overcome. The effect of different salts on electrospinning of polyacrlonitrile (PAN) polymer solution was investigated in this article. The various inorganic salts used in this work include LiCl, NaNO3, NaCl, and CaCl2.The results show that when the salts were added, respectively, into different concentrations of PAN solution, the order of conductant was LiCl > NaNO3 > CaCl2 > NaCl > no salt added. Viscosity and shearing strength of electrospinning solutions are slightly affected by the adding of salts and mainly affected by the changes in concentration of PAN electrospinning solutions. The diameter of nanofibers electrospun by solutions with different salts size down as follows: LiCl > NaNO3 > CaCl2 > NaCl. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3865–3870, 2007

Electrospun nanofibrous polysulfone membranes as pre-filters: Particulate removal

This paper explores the viability of developing high surface area pre-filters through electrospinning. Pre-filters are regularly used in removing particulate contaminants that can have a deleterious effect on downstream membrane elements such as ultrafiltration and nanofiltration. They should possess high internal surface area and thus sub-micron size fibers are ideal. In this study, polysulfone nanofibers were electrospun into membranes and their ability to remove micro-particles from solution was investigated. The nanofibrous membranes possess high porosity together with high surface area to produce high flux pre-filters with high loading capacity. The membrane had a bubble-point of 4.6 μm and was able to remove above 99% of 10, 8 and 7 μm particles without any permanent fouling. However, the membrane was observed to foul irreversibly by 2 and 1 μm particles with a ‘cake-layer’ forming on the membrane surface. Below 1 μm, the membrane behaved as a depth filter with 0.5 and 0.1 μm particles being attracted onto the nanofiber surface. This study highlights that nanofibers do have potential as pre-filters for particulate removal. Such nanofibrous pre-filters can be used in various applications such as removal of micro-particles from waste-water, prior to ultrafiltration or nanofiltration membranes, to prolong the life of these membranes.

Effect of Blend Ratio and Draw Ratio on the Mechanical Properties of PET/PP Blended Conjugate Fibers

This study analyzes the influence of blend ratio and draw ratio on the fiber properties of blend fibers composed of poly (ethylene terephthalate), or PET, and polypropylene, or PP, (hereafter referred to as PET/PP conjugate fibers). For a comparison, PET and poly (butylene terephthalate), or PBT blends, (hereafter referred to as PET/PBT conjugate fibers) are also investigated. Various blend ratios of fibers are melt spun and drawn in a multistep drawing method. The conjugate fibers are evaluated using tenacity, Young's modulus, wide-angle X-ray diffraction, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) tests. The results show that multistep drawing using a lower first-step draw ratio provides a higher tenacity and Young's modulus. Furthermore, when the blend ratio is 75/25 in a PET/PP conjugate fiber and 50/50 in a PET/PBT conjugate fiber, the polymer components undergo a phase inversion phenomenon. A PP sub-micron (10−1 ∼ 100 micron) fiber of about 0.0001 ∼ 0.00017 tex in fineness, or about 0.4 ∼ 0.5 micron in diameter, can be obtained when PET/PP conjugate fiber is treated with a 25% NaOH aqueous solution by weight. However, A PBT sub-micron fiber cannot be achieved using a PET/PBT conjugate fiber.

The thermal effects on electrospinning of polylactic acid melts

We demonstrate that melt electrospinning can be a feasible way to produce sub-micron scale polylactic acid (PLA) fibers in this paper. This solvent-free approach to produce sub-micron scale fibers is more environmentally benign than common solution electrospinning processes, and has a potential to increase the production rate significantly. Our experimental results show that temperatures at the spinneret and in the spinning region are critical to produce sub-micron sized fibers: a high-speed photographic investigation reveals that when spinning temperature is below glass transition temperature, whipping of the jet is suppressed by fast solidification in the spinning region, leading to a larger jet diameter. Both thermal and mechanical degradations of PLA in melt electrospinning can be significant but no change in chemical composition is found. Due to rapid solidification, melt electrospun PLA fibers are mostly amorphous, and the small presence of β crystals is noted in the sub-micron scale PLA fibers by XRD studies. The highly oriented structure of PLA fibers gives rise to cold crystallization at around 95 °C, and the degree of crystallinity of fibers increases with increasing the degree of annealing. Finally, PLA nanofibers have directly been electrospun onto cellulose filter media, and a drastic enhancement in collection efficiency of sub-micron sized dust particles is presented. Melt electrospun PLA nanofiber mats with no residual solvent may serve as better filter media and tissue scaffolds than those obtained from solution electrospinning processes.

Biodegradable Nanomats Produced by Electrospinning: Expanding Multifunctionality and Potential for Tissue Engineering

With increasing interest in nanotechnology, development of nanofibers (n-fibers) by using the technique of electrospinning is gaining new momentum. Among important potential applications of n-fiber-based structures, scaffolds for tissue-engineering represent an advancing front. Nanoscaffolds (n-scaffolds) are closer to natural extracellular matrix (ECM) and its nanoscale fibrous structure. Although the technique of electrospinning is relatively old, various improvements have been made in the last decades to explore the spinning of submicron fibers from biodegradable polymers and to develop also multifunctional drug-releasing and bioactive scaffolds. Various factors can affect the properties of resulting nanostructures that can be classified into three main categories, namely: (1) Substrate related, (2) Apparatus related, and (3) Environment related factors. Developed n-scaffolds were tested for their cytocompatibility using different cell models and were seeded with cells for to develop tissue engineering constructs. Most importantly, studies have looked at the potential of using n-scaffolds for the development of blood vessels. There is a large area ahead for further applications and development of the field. For instance, multifunctional scaffolds that can be used as controlled delivery system do have a potential and have yet to be investigated for engineering of various tissues. So far, in vivo data on n-scaffolds are scarce, but in future reports are expected to emerge. With the convergence of the fields of nanotechnology, drug release and tissue engineering, new solutions could be found for the current limitations of tissue engineering scaffolds, which may enhance their functionality upon in vivo implantation. In this paper electrospinning process, factors affecting it, used polymers, developed n-scaffolds and their characterization are reviewed with focus on application in tissue engineering.

Filtration properties of electrospinning nanofibers

AbstractElectrospinning is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. The extensive application in future of electrospinning nanofibers is filtration. In this article, the filtration properties of electrospinning nanofibers were investigated. During the experiments, nanofibers layers with different area weight were electrospun on the spunbonded or meltblown sublayers. Fiber diameter, pore diameter, filtration efficiency as well as filtration resistance of nanofibers web and sublayers were measured, respectively, through a series of experiments. The results show that the fiber diameter of nanofibers is much smaller than that of sublayers. It is also found that the pore diameter of nanofibers web is much smaller than sublayers and coefficient variation of the pore diameter of nanofibers web is much smaller than sublayers. Moreover, the filtration efficiency and filtration resistance of sublayers are lower than nanofibers webs. The balance between efficiency and press drop is also investigated in the article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1285–1290, 2006

Poly(dicyclopentadiene) Submicron Fibers Produced by Electrospinning

Summary: We have used the process of electrospinning to produce fibers of poly(dicyclopentadiene) with diameters on the submicron scale. The material, formed from a monomer-catalyst solution, polymerized in flight during the electrospinning process. Fibers were collected over trenches etched in silicon and the Young's moduli were measured using an atomic force microscope to measure force-displacement curves. The resulting values of Young's moduli are larger than typical values for bulk polymer material. SEM image of suspended PDCPD fiber.

Continuous polymer nanofibers by extrusion into a viscous medium: A modified wet-spinning technique

We present a wet-spinning technique capable of producing continuous polymer nanofibers. This method involves injecting a solvated polymer into a highly viscous moving medium through a microaperture. The extruded fiber moves in a predictable spiral path and is collected around a spinning mandrel which also serves to pull the extruded fiber away from the aperture. Semicontinuous, solid nanofibers of polyvinyl butyral were produced with diameters ranging from 10μmto400nm. Electron microscopy indicates that submicron fibers exhibit a ribbonlike morphology. The effect of different processing parameters on the fiber size and shape is discussed.