Electrospun Polymer Fibers Research Articles

Dye-doped electrospun fibers for use as random laser generator: The influence of spot size and scatter concentration

The development of electrospun polymer fiber networks embedded with metal oxide nanoparticles in organic dye media favors the photons waveguiding and multiple scattering, providing the adequate environment for random laser action. The use of water-soluble polymer solution as support for electrospun matrix introduces relevant application in biomedical applications. Herein, it is explored the use of block copolymers (Eudragit L100) as support for electrospinning of polymer fiber doped with titanium dioxide (scatter centers) and rhodamine B (gain media). The resulting fiber net presented random laser behavior that depends on aggregation degree of gain media (rhodamine B) due to the combination of reabsorption/reemission processes with tunable response (emission peak position). These results open new possibilities for use of low-cost and water soluble electrospun-based random lasers based on organic dyes and random network of polymer matrix.

Alignment‐Improved and Diameter‐Reduced Electrospun Polymer Fibers via the Hot‐Stretching Process

AbstractElectrospinning is one of the most facile and versatile techniques to prepare polymer fibers ranging from micrometers to nanometers. Although several parameters can be tuned to control the sizes and morphologies of electrospun fibers, many obstacles are still encountered as the target sizes of the fibers are getting smaller; for example, the sizes of the fibers can be effectively reduced by lowering the polymer solution concentrations but beaded or beads‐on‐string structures are usually formed. To overcome such obstacles, here a simple technique to prepare alignment‐improved and diameter‐reduced fibers without bead formation by hot‐stretching electrospun fibers at temperatures higher than the glass transition temperatures of the polymers is developed. Polystyrene and poly(methyl methacrylate) are both used in this work as model materials. The relationship between the draw ratio and diameter of the fibers is quantitatively analyzed, demonstrating the control of the fiber diameters. Moreover, higher degrees of alignment improvement at the middle part of the fibers than those at the end part is observed, which results in lower water contact angles at the middle part of the fibers. This work provides a useful post‐treatment technique to control the sizes and orientations of electrospun polymer fibers.

Rapid Release Polymeric Fibers for Inhibition of Porphyromonas gingivalis Adherence to Streptococcus gordonii.

Active agents targeting key bacterial interactions that initiate biofilm formation in the oral cavity, may alter periodontitis progression; however, to date, specifically-targeted prophylactic and treatment strategies have been limited. Previously we developed a peptide, BAR (SspB Adherence Region), that inhibits oral P. gingivalis/S. gordonii biofilm formation in vitro and in vivo, and BAR nanoparticles that increase BAR effectiveness via multivalency and prolonged delivery. However, limited BAR loading and nanoparticle retention in the oral cavity can result in inadequate release and efficaciousness. Given this, an effective delivery platform that can release concentrations of BAR suitable for twice-daily applications, may offer an alternative that enhances loading, ease of administration, and retention in the oral cavity. With this in mind, the study objectives were to develop and characterize a rapid-release platform, composed of polymeric electrospun fibers (EFs) that encapsulate BAR, and to evaluate fiber safety and functionality against P. gingivalis/S. gordonii biofilms in vitro. Poly(lactic-co-glycolic acid) (PLGA), poly(L-lactic acid) (PLLA), and polycaprolactone (PCL) were electrospun alone or blended with polyethylene oxide (PEO), to provide high BAR loading and rapid-release. The most promising formulation, 10:90 PLGA:PEO EFs, provided 95% BAR release after 4 h, dose-dependent inhibition of biofilm formation (IC50 = 1.3 μM), disruption of established dual-species biofilms (IC50 = 2 μM), and maintained high cell viability. These results suggest that BAR-incorporated EFs may provide a safe and specifically-targeted rapid-release platform to inhibit and disrupt dual-species biofilms, that we envision may be applied twice-daily to exert prophylactic effect in the oral cavity.

Impact of the Fiber Length Distribution on Porous Sponges Originating from Short Electrospun Fibers Made from Polymer Yarn

AbstractUltralight highly porous sponges made of short electrospun polymer fibers have gained significant attention for a variety of applications. According to the established procedures, short electrospun fibers are obtained by cutting or homogenization of electrospun fibers in suspension, which yield fibers with inhomogeneous fiber length. The role of the fiber length distribution and the fiber length in the mechanical compressibility of the sponges is unknown. Therefore, as a model study, sponges made from suspensions of short electrospun poly(acrylonitrile) (PAN) fibers with controlled fiber length distribution are investigated, and the role of the fiber length distribution in the compressibility of the sponges is analyzed quantitatively. These sponges are also compared to the ones prepared by established procedure as a benchmark. It is found that the compression stress and modulus of ultralight sponges with monodisperse short fibers are respectively 32% and 45% higher than that made with polydisperse short fibers. The study also shows that sponges made from longer fibers have higher modulus in comparison to the sponges made from shorter fibers.

Omnidirectionally stretchable electrodes based on wrinkled silver nanowires through the shrinkage of electrospun polymer fibers

An omnidirectionally stretchable electrode has been developed by utilizing wrinkled Ag NWs through the controllable shrinkage of electrospun fluoroelastomer fiber mats.

Improvements on electrical conductivity of the electrospun microfibers using the silver nanoparticles

ABSTRACTConductive electrospun polymer fibers have attracted a great deal of interest in recent years. This study describes the preparation of electrically conductive microfibers composed of polyethersulfone/polydopamine/silver nanoparticles (PES/PDA/Ag NPs). Ag NPs acted as conductive centers, while hydroxyl‐ and amino‐rich functional groups and excellent adhesion properties of PDA served to connect the Ag NPs and PES microfibers. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) showed that PDA was firmly adhered to PES microfibers. PES/PDA microfibers absorbed considerable amounts of silver ion from AgNO3 solution, resulting in Ag NPs. X‐ray diffraction, X‐ray photoelectron spectroscopy, and SEM data represented the successful formation of PES/PDA/Ag NPs microfibers. Microfibers with optimal conductivity were obtained using a solution of 2% AgNO3 at pH 9 at 50 °C for 45 min. The electrical resistivity of our PES/PDA/Ag NPs microfibers was only 202 Ω/cm, much lower than that of regular PES microfibers (2.1 × 109 Ω/cm). These results show that the PES/PDA/Ag NPs microfibers are suitable for use as conductive polymer fibers in electromagnetic shielding, and conductivity‐sensing applications, and in flexible electronic devices and biosensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48788.

Electrospinning in the preparation of an electrochemical sensor based on carbon nanotubes

This paper reports the development of an electrochemical sensor using electrospun polymeric fibers of PBAT (poly (butylene adipate co-terephthalate))/PLA (poly (lactic acid) containing functionalized carbon nanotubes (MWCNTs) and further calcined (at 500 °C under N2). The morphologies of the electrospun fibers were verified by SEM and those containing MWCNTs presented lower average diameter of 1.76 ± 0.30 μm against 3.67 ± 0.88 μm for the fibers of neat PBAT/PLA. Fourier transform infrared (FTIR) spectra of the polymeric fibers indicated possible interactions between the MWCNTs and the CO functional group. Thermogravimetric analysis (TGA) curves demonstrated slight increase of the stability of the PLA and lower thermal stability of the PBAT. Analyzes through differential scanning calorimetry (DSC) data showed that the interactions occur preferentially with the aliphatic segments of polymer chains; and corroborated the data from FTIR. Also, FTIR and X-ray powder diffraction (DRX) indicated, respectively, decrease on carboxylic groups amount and lamella formation on functionalized MWCNTs due to the PBAT/PLA/MWCNTs electrospun fibers calcination. The electrochemical measurements performed using sensor built based on the as-obtained calcined material showed that the sensor is promising for the determination of metronidazole in aqueous environment.

Highly-sensitive SERS-based immunoassay platform prepared on silver nanoparticle-decorated electrospun polymeric fibers

A new, highly sensitive surface enhanced Raman scattering (SERS)-based immunoassay platform was prepared using silver nanoparticle (AgNP)-decorated electrospun fibers as the capture substrate. We used electrospinning and silver mirror reaction to generate AgNP-decorated polycaprolactone (PCL) fiber matrix (Ag-PCL). The resultant capture substrates obtained were bi-directionally porous, free-standing, and flexible. AgNP formation on the PCL fibers was confirmed via SEM, AFM, XPS, and TGA analysis. In addition, gold nanoparticles immobilized with a Raman reporter, 4-mercaptobenzoic acid (4-MBA), were prepared as the SERS tag. This tag could significantly enhance the SERS signal via generation of additional hot spots between AgNPs on fibers and AuNPs. For a model immunoassay to detect prostate specific antigen (PSA), PSA antibodies were immobilized on both Ag-PCL and AuNP SERS tags. The large surface area of fiber substrates allowed the immobilization of large amounts of antibodies and their porous structures facilitated the assessment of the target antigen to immobilized antibodies. Binding of PSA between antibodies on AgNPs and AuNPs led to formation of a sandwich structure by the two metal nanostructures, and consequently, highly sensitive detection of PSA was possible up to a detection limit of 1pg/mL within 1h of reaction time. The developed SERS-based immunoassay platform produced uniform and reproducible SERS signals over the entire substrate area and from different samples.

Wire Melt Electrospun Polymer Nanocomposite Fibers as Radio Frequency Responsive Heaters

We have demonstrated noncontact heating of melt electrospun polymer fibers by using radio-frequency (RF) fields which heat carbon nanotube (CNT) receptors inside the fibers. RF radiation is attractive as it allows for noncontact heating of polymers with low concentrations of CNTs. We observed that the heating rate scales with the CNT loading even below the bulk electrical percolation threshold, suggesting that individual CNTs can serve as RF receptors/heat sources. This capability eliminates the requirement for a percolated network of CNTs inside a fiber as a means to enable heating. We also showed that a strong radial temperature gradient will develop within the fibers. For a 2 μm diameter fiber, the temperature of the core is 10–15 °C higher than the surface. Hence, the temperature of the core can surpass the melting temperature inside the fiber without altering the morphology of the fibers (i.e., without fusing between fibers). These electrospun fibers that can be stimulated through RF energy can be us...

Whispering gallery mode microlaser based on a single polymer fiber fabricated by electrospinning

Electrospinning is a very simple method of preparing polymer solutions into high performance fibers. In this work, PM597-doped polymer fibers with different diameters have been fabricated by electrospinning technology. Whispering gallery mode (WGM) lasing emission was observed when a 532 nm pulse laser beam radially excited the single electrospun polymer fiber (EPF) created by this method. The distribution of WGMs is also quantitatively confirmed through theoretical calculation. Additionally, the number of WGM laser peaks decrease as the diameter of the EPF decreases. Single longitudinal mode laser emission can be obtained when the EPF diameter decreases to 8.8 µm. It has also been found that the WGM laser from the single EPF has relatively low thresholds and good lifetime compared to droplet lasers or other fiber lasers. Moreover, EPF networks have unique research prospects in photonic devices, optical pump lasers and biosensing due to their very large surface to volume ratio.

Energy‐Transfer Random Laser: Replica Symmetry Breaking in FRET‐Assisted Random Laser Based on Electrospun Polymer Fiber (Ann. Phys. 9/2019)

In article number 1900066, Zhijia Hu and co-workers investigate a FRET-assisted random laser based on an electrospun polymer fiber. They find that the FRET efficiency can be controlled by modulating the donor–acceptor ratio. Meanwhile, the statistical association between the random laser with other complex physical systems is illustrated by experimental evidence of the replica symmetry breaking in a random laser with multiple energy levels.

Stable-jet length controlling electrospun fiber radius: Model and experiment

Generally, the precise prediction and control on the radius of electrospun polymer fibers is critical for their applications but still remains challenging. In the current work, a model has been established to predict the radius. It is shown that the correlation between the stable-jet length and the terminal fiber radius satisfies a scaling law with a power exponent −2/3 for fully charged fibers, while the exponent becomes smaller for the case in which the fibers are partly charged on surface during electrospinning. And a good agreement between the experimental and theoretical values for electrospinning poly(methyl methacrylate) (PMMA) fibers is obtained, thus further verifying the correctness of derived model between the stable-jet length and the terminal fiber radius.

Hierarchical and Spiral Polymer Structures: Direct Electrospinning on Porous Anodic Aluminum Oxide Templates

AbstractElectrospun fibers with hierarchical structures have attracted a great deal of attention because they have distinct properties, such as large specific surface areas and high surface area‐to‐volume ratios, and can be applied to various fields. Here, a simple and versatile method is demonstrated to prepare electrospun fibers with hierarchical structures by directly electrospinning poly(methyl methacrylate) (PMMA) solutions on porous anodic aluminum oxide (AAO) templates. Hierarchical PMMA structures with micro‐ and nanometer scales can be generated. The two length scales of the hierarchical structures can be independently controlled; the first length scale is controlled by the electrospinning conditions, and the second length scale is controlled by the pore sizes of the AAO templates. By adding water in the polymer solutions, the evaporation of the solvents and the whipping instability of the solution jets can be manipulated. Consequently, spiral and hierarchical structures can be obtained. This study opens a promising avenue in fabricating electrospun polymer fibers with hierarchical structures, which should have great potential in a variety of applications, such as filtration, diagnosis, and tissue regeneration.

Enhanced Mechanical Damping in Electrospun Polymer Fibers with Liquid Cores: Applications to Sound Damping

Multicompartmental “core–sheath” fibers composed of a poly(caprolactone) (PCL) polymer sheath and poly(ethylene glycol) (PEG) fluids as the core materials were designed via coaxial electrospinning. Mechanical stretching of the fibers caused a discontinuous mechanical damping or stiffening behavior when the cores were composed of a PEG fluid as a known non-Newtonian shear thickening fluid (PEG and SiO2 particles). Surprisingly, it is found that shear thickening fluids are not a requirement for mechanical damping as is evidenced by similar behavior with Newtonian viscous PEG liquids. Data from optical microscopy, thermogravimetric analysis, dynamic mechanical analysis, and rheology have been employed to gain insights into the interactions between the PCL sheath and the PEG cores. The degree of mechanical damping was found to correlate with the viscosity of the core PEGs and is discussed in terms of the interactions between the core and sheath during mechanical oscillation. In addition, the nonwoven fiber ma...

Growth factor releasing core-shell polymeric scaffolds for tissue engineering applications.

Tissue engineering is the use of a combination of cells, biomaterials and appropriate signals to repair or improve the functions of damaged tissues. Our group is exploiting various approaches to effectively encapsulate multiple growth factors in polymeric scaffolds for tissue engineering and wound healing applications. In this report, some of the exciting results from our most recent and ongoing projects are outlined with a focus on the use of connective tissue growth factor (CTGF). CTGF is a secreted protein with major roles in angiogenesis, chondrogenesis, osteogenesis and tissue repair. CTGF can play a major role in tissue regeneration by enhancing cell proliferation and promoting cell migration. CTGF was incorporated to electrospun polymeric fibers to provide sustained release. Experimental results demonstrated the ability of scaffolds incorporated with CTGF to promote cell proliferation and cell migration. This study shows the application potential of the developed scaffolds in various tissue engineering applications.

Numerical study on effective thermal conductivity of transparent electrospun polymer composite

With the increased power of optoelectronic devices, enhancing thermal conductivities of transparent materials is key to thermal dissipation. Recently, our group has experimentally demonstrated a novel composite material with both high thermal conductivity and transparency by electrospinning. In this study, a numerical model was built to explore the effective thermal conductivity of the composite with non-overlapping electrospun polymer fibers and solved by the finite element method. Effects of the side length of a representative volume element and thermal conductivity along different directions of the composite were investigated by the model by adjusting the size and angle of the representative volume element. In the meanwhile, the effects of fiber volume and fiber orientation on the effective thermal conductivity were analyzed which is realized by controlling the fiber orientation with normal distribution. The generated models consisted of randomly distributed long fibers. Moreover, the overlapping methods of fiber films were studied to optimize the thermal dissipation. The electrospun composite was applied on a light emitting diode (LED) modules in a simulation way. In those modules, simulated effective thermal conductivity of the electrospun composite was applied and the temperature reduction on phosphor of the modules have been studied. This study provides a deeper understanding of effective thermal conductivity of composite that is reinforced by continuous long fibers and a useful tool to simulate the effective thermal conductivity with desired fiber volume fraction and fiber orientation.

Replica Symmetry Breaking in FRET‐Assisted Random Laser Based on Electrospun Polymer Fiber

AbstractSpin‐glass theory has been widely introduced to describe the statistical behaviors in complex physical systems. By analogy between disorder photonics and other complex systems, the glassy behavior, especially the replica symmetry breaking (RSB) phenomenon, has been observed in random lasers. However, previous studies only analyzed the statistical properties of the random laser systems with single gain material. Here, the first experimental evidence of the glassy behavior in a random laser with complex energy level structure is reported. This novel random laser is demonstrated based on the electrospun polymer fibers with the assistance of Förster resonance energy transfer (FRET). The electrospinning technology employed in the experiment herein promises high‐volume production of random laser devices with multiple energy levels, enabling the comprehensive investigation of lasing properties in multi‐energy level random laser system. Clear paramagnetic phase and spin‐glass phase are observed in the FRET‐assisted random laser under different pump energies. The RSB phase transition is verified to occur at the laser threshold, which is robust among the random lasers with different donor–acceptor ratio. The finding of RSB in FRET‐assisted random laser provides a new statistical analysis method toward the laser system with complex energy level, for example, quantum cascade laser.

A Comparative Study of Multifunctional Coatings Based on Electrospun Fibers with Incorporated ZnO Nanoparticles

In this work, polymeric fibers of polystyrene (PS) with incorporated ZnO nanoparticles have been deposited onto an aluminum alloy substrate (6061T6) by using the electrospinning technique. In order to optimize the deposition process, the applied voltage and flow rate have been evaluated in order to obtain micrometric electrospun fibers with a high average roughness and superhydrophobic behavior. Thermogravimetric analysis (TGA) has also been employed in order to corroborate the amount of ZnO incorporated into the electrospun fibers, whereas differential scanning calorimetry (DSC) has been performed in order to determine the glass transition temperature (Tg) of the polymeric electrospun fibers. In addition, a specific thermal treatment (Tg + 20 °C) of the synthesized electrospun fibers has been evaluated in the resultant corrosion resistance. A comparative study with previously reported results corresponding to polyvinyl chloride (PVC) fibers is carried out along this paper to show the changes in behavior due to the different compositions and fiber diameters. The coating has produced an important reduction of the corrosion current of the aluminum substrate in two orders of magnitude, showing also an important enhancement against pitting corrosion resistance. Finally, this deposition technique can be used as an innovative way for the design of both superhydrophobic and anticorrosive surfaces in one unique step over metallic substrates with arbitrary geometry.

Porous Aromatic Framework Modified Electrospun Fiber Membrane as a Highly Efficient and Reusable Adsorbent for Pharmaceuticals and Personal Care Products Removal.

Water contamination by emerging organic pollutants, such as pharmaceuticals and personal care products (PPCPs), is becoming more and more serious. Porous aromatic frameworks (PAFs) are considered as promising adsorbents to remove the PPCPs. To overcome the limitation of PAFs in their powder forms for large-scale applications, herein, we proposed a strategy to covalently anchor PAFs onto electrospun polymer fiber membranes. Polyaniline (PANI) played the role of aromatic seed layer, which was coated on the electrospun polyacrylonitrile (PAN) fiber membrane first. Then, PAF-45 modification was in situ synthesized in the presence of the PANI-coated electrospun PAN fiber membrane. This study could make the PAF-based materials be handled more easily and improve the surface area of electrospun fiber membrane. The obtained composite adsorbent (PAF-45-PP FM) was applied for the adsorption of three PPCPs: ibuprofen (IBPF), chloroxylenol (CLXN), and N, N-diethyl-meta-toluamide (DEET), which exhibited high adsorption capacity and good recycling ability. According to the Langmuir model, the maximum adsorption capacities of PAF-45-PP FM toward IBPF, CLXN and DEET were 613.50, 429.18, and 384.61 mg/g, respectively. In addition, after ten adsorption-desorption cycles, the adsorption capacities toward the three PPCPs decreased slightly. Through an adsorption comparison test, the adsorption capacity of PAF-45-PP FM almost attributed to the loading PAF-45. The adsorption mechanism analysis illustrated that there were pore capture, hydrophobic interaction and π-π interaction between PPCPs and PAF-45-PP FM. Therefore, the PAF-45-PP FM can be potential adsorbents to purify water contaminated with PPCPs.

Improvement of carbon nanotube dispersion in electrospun polyacrylonitrile fiber through plasma surface modification

ABSTRACTIn this study, surfaces of multiwalled carbon nanotubes (CNTs) were functionalized with poly(hexafluorobutyl acrylate) (PHFBA) thin film using a rotating‐bed plasma‐enhanced chemical vapor deposition (PECVD) method without imparting any defects on their surfaces. Polyacrylonitrile (PAN) electrospun polymer fiber mats and composite fiber mats with CNTs and functionalized CNTs (f‐CNTs) were prepared. The wettability and chemical and morphological properties of the synthesized fiber mats were investigated, and the dispersion of CNTs and f‐CNTs in the polymer matrix was compared according to the contact angle results of electrospun polymer mats. According to the chemical and morphological characterization results, PHFBA‐coated CNTs were dispersed more uniformly in the polymer matrix than the uncoated CNTs. The f‐CNTs/PAN composite fiber mat exhibits a lower surface energy than the pristine CNTs/PAN fiber mat. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47768.