Uniform Fiber Diameter Research Articles

The effect of different solvent systems on physical properties of electrospun poly(glycerol sebacate)/poly(ɛ-caprolactone) blend

ABSTRACT Solvent type and solution viscosity are of great importance in affecting different traits of the electrospun scaffolds. This study aims to highlight the effect of different solvents on physicomechanical properties of PGS/PCL blend electrospun scaffolds. The PGS:PCL (2:1) blends were dissolved in five different solvent systems including DMF, DCM, DMSO, CF-AC, and CF-EtOH, with the final concentration of 18% w/v. Analyzing morphology indicated a more uniform fiber diameter and smaller pore size in PGS/PCL//CF-AC scaffolds. Also, the mechanical parameters were improved by the solvent upon using CF-AC more than DMF, correlated to better solution viscosity, spinnability and uniform fiber distribution.

Fabrication of biodegradable facemask layer using polylactic acid: Effect of flowrate on fiber forming properties

The research on biodegradable polymers for facemask applications is on full swing to reduce the environmental impacts caused due to the nonbiodegradable petroleum-based polymers. Polylactic acid (PLA) is one of the most famous biodegradable polymers, hence fabricating facemask using polylactic acid through electrospinning could provide an effective solution. Among various parameters of electrospinning, flow rate plays a significant role in fiber forming properties of electrospun nanofiber. In this study, the influence of varying flow rate on fiber forming properties were investigated in order to determine the optimum parameters to fabricate uniform PLA nanofibers. The nanofibers produced were characterized for fiber diameter, thickness and surface morphology and were compared with the commercial facemask. It was found that the flow rate of 1.5 mL/h provides uniform fiber diameter, thickness and surface morphology which can provide better protection similar to that of a commercial facemask.

The influence of working distance, stirring and electrospinning time on fibre forming properties of electrospun polylactic acid for facemask layer application

Polylactic acid (PLA) polymers are emerging as a viable alternative biodegradable polymer to fabricate a new filtration layer for facemask application; however, it is still in the early stages of development. The objectives of this study was to fabricate a PLA layer by using electrospinning process. For the fabrication of the new layer, the electrospinning parameters such as working distance, electrospinning time and solution stirring time were varied. The processing parameters were studied to identify the most suitable framework for the fabrication of the new PLA fibre mat comparable to the commercial facemask (CFM) in terms of thickness and fibre diameter. Based on the result, it was found that 9 cm working distance, 1 h of electrospinning and 48 h of solution stirring time showed the best results for uniform fibre thickness and diameter.

Preliminary Characterization of a Polycaprolactone-SurgihoneyRO Electrospun Mesh for Skin Tissue Engineering.

Skin is a hierarchical and multi-cellular organ exposed to the external environment with a key protective and regulatory role. Wounds caused by disease and trauma can lead to a loss of function, which can be debilitating and even cause death. Accelerating the natural skin healing process and minimizing the risk of infection is a clinical challenge. Electrospinning is a key technology in the development of wound dressings and skin substitutes as it enables extracellular matrix-mimicking fibrous structures and delivery of bioactive materials. Honey is a promising biomaterial for use in skin tissue engineering applications and has antimicrobial properties and potential tissue regenerative properties. This preliminary study investigates a solution electrospun composite nanofibrous mesh based on polycaprolactone and a medical grade honey, SurgihoneyRO. The processing conditions were optimized and assessed by scanning electron microscopy to fabricate meshes with uniform fiber diameters and minimal presence of beads. The chemistry of the composite meshes was examined using Fourier transform infrared spectroscopy and X-ray photon spectroscopy showing incorporation of honey into the polymer matrix. Meshes incorporating honey had lower mechanical properties due to lower polymer content but were more hydrophilic, resulting in an increase in swelling and an accelerated degradation profile. The biocompatibility of the meshes was assessed using human dermal fibroblasts and adipose-derived stem cells, which showed comparable or higher cell metabolic activity and viability for SurgihoneyRO-containing meshes compared to polycaprolactone only meshes. The meshes showed no antibacterial properties in a disk diffusion test due to a lack of hydrogen peroxide production and release. The developed polycaprolactone-honey nanofibrous meshes have potential for use in skin applications.

Expanding Melt‐Based Electrohydrodynamic Printing of Highly‐Ordered Microfibrous Architectures to Cm‐Height Via In Situ Charge Neutralization

AbstractIt is a great challenge for melt‐based electrohydrodynamic (EHD) printing to fabricate cm‐height microfibrous scaffolds with uniform fiber diameter and highly‐ordered architectures due to inherent charge‐induced fiber repulsion and gradually‐reduced electrical strength. Here, a novel approach is presented that involves incorporating the in situ charge neutralization technique into the melt‐based EHD printing process. The addition of the charge elimination module can efficiently neutralize residual charges inside the EHD‐printed microfibers and minimize fiber–fiber repulsion to ensure precise fiber deposition. Computational simulation indicates that the applied voltage should increase ≈0.15 kV as the printed structure height increases 1 mm to maintain a relatively constant electrical strength. The implementation of these two strategies in melt‐based EHD printing successfully produces highly‐ordered fibrous architectures with a maximum height of 10.01 ± 0.18 mm and a uniform fiber diameter of 17.6 ± 1.3 µm. The resultant microfibrous architectures can guide large‐area cellular alignment in 3D and function as supporting frames to reinforce mechanically‐weak collagen hydrogel for engineering large‐volume cellular constructs. To the authors’ best knowledge, it is the first instance of directly producing cm‐height, highly‐ordered microfibrous architectures via melt‐based EHD printing with in situ charge neutralization and constant electrical strength capabilities for tissue‐engineering applications.

Polyamide/Chitosan/Tetraethyl Orthosilicate Electrospun Nanofibers for a Novel and Promising Drug Carrier.

Chitosan (CS), the only alkaline polysaccharose available in nature, has always been a promising candidate for drug delivery owing to its excellent biodegradability and biocompatibility. However, inherent solubility and polycationic properties of CS largely hinder electrospinning, which is an efficient method of fabricating nanofibers for drug carriers. To solve this problem and extend the applications of CS, polyamide/chitosan/tetraethyl orthosilicate (PA/CS/TEOS) composite nanofibers were successfully prepared as drug carriers in this study via electrospinning. The PA/CS/TEOS ratios significantly influenced the nanofiber morphology. As the content of each was increased, the beads among the membranes increased initially and then decreased, determined by scanning electron microscopy (SEM). The morphology of the optimum membranes with the ratio of 1:0.13:0.67 was smoother with less beads and uniform fiber diameter. Finally, the membranes with optimum ratios were used as carriers of ofloxacin in the study of drug release performance to identify their future feasibility, which revealed an initial fast release followed by a relatively stable release.

ELECTROSPINNING OF ST. JOHN'S WORT OIL LOADED MICROCAPSULES BASED PVA NANOFIBERS

In this study, it was achieved that the production of St. John's Wort oil loadad Eudragit RS 100/PVA microcapsules by emulsion/solvent evaporation method and the microcapsules were embedded in PVA nanofibers. Morphological analysis was carried out with SEM images of both microcapsules and nanofibers. The presence of St. John's Wort oil, PVA and Eudragit RS 100 polymers were confirmed in the chemical structure of microcapsules and nanofibers by FT-IR. According to experimental studies, microcapsules were produced to have a smooth surface, a spherical shape and a uniform particle size. The PVA concentration was kept constant at 10% wt and microcapsule concentrations were applied as 1, 3, 5, 7, and 9 wt %. Then, polymer solution properties were measured, such as conductivity, viscosity, and surface tension. It was determined that viscosity and surface tension values increased with microcapsule concentration increase, while conductivity did not change significantly. Nanofiber production was realized via the electrospinning method under the optimum process parameters. According to the SEM images and histogram, nanowebs have a fine fiber diameter, smooth surface, high quality and no bead structure. In addition, the average microcapsule size is 30 μm, average fiber diameter is 430 nm and the fiber diameter uniformity coefficient is 1,014. It is thought that this nanofiber surface containing microcapsules embedded in St. John's Wort has the potential to be used as a wound dressing.

Novel silicon‐contained lignin‐based carbon fibers derived from bamboo pulping black liquor with improved electrochemical performance for supercapacitors

AbstractCarbon fibers (CFs) are a promising candidate as electrode materials for flexible supercapacitors given its light weight and moderate cost. In this study, the lignin used was partially separated from kraft bamboo pulping black liquor and the higher molecular weight fraction, unavoidably contains a small amount of silicon compounds, so named silicon‐contained lignin. Novel CFs were prepared using commercial polyacrylonitrile (PAN) and the lignin by electrospinning and further carbonization. Even in the presence of silicon compounds, the fibrous morphology of precursor fibers was significantly good, and the CFs with uniform fiber diameter and high specific surface area up to 182 m2/g were obtained with an increase in silicon‐contained lignin. The CFs fabricated from silicon‐contained lignin and commercial PAN had higher specific capacitance (22.20 mF/cm2at 10 mA/cm2) and superb cycling stability (94.21%) than that from silicon‐free lignin or pure PAN separately.

Centrifugally spun starch/polyvinyl alcohol ultrafine fibrous membrane as environmentally‐friendly disposable nonwoven

AbstractWe developed a new environmentally‐friendly disposable nonwoven based on centrifugally spun ST/PVA ultrafine fibrous membrane in this research. The effects of ST/PVA ratio as well as formic acid post‐treatment on thermal properties, tensile strength, and disposability of fibrous membranes were studied. To observe the morphology and chemical structures changing of fibers during fabrication and post‐treatment, the obtained fibers were characterized by scanning electron microscopy, x‐ray diffraction, and Fourier transform infrared spectroscopy. The fibrous membranes with uniform fiber diameters and excellent disposability properties were formed. The ST/PVA ratio of fibers was optimized according to the disposability and tensile strength of the fibrous membranes. Disintegration of untreated and post‐treatment fibrous membrane with ST/PVA ratio of 3/1 was over 80% and 40%, respectively, and the tensile strength was improved over two times comparing with pure starch fibrous membrane.

On collapsing Calabi–Yau fibrations

We develop some techniques to study the adiabatic limiting behaviour of Calabi–Yau metrics on the total space of a fibration, and obtain strong control near the singular fibres by imposing restrictions on the singularity types. We prove a uniform lower bound on the metric up to the singular fibre, under fairly general hypotheses. Assuming a result in pluripotential theory, we prove a uniform fibre diameter bound for a Lefschetz K3 fibred Calabi–Yau $3$‑fold, which reduces the study of the collapsing metric to a locally non-collapsed situation, and we identify the Gromov–Hausdorff limit of the rescaled neighbourhood of the singular fibre.

Melting centrifugally spun ultrafine poly butylene adipate-co-terephthalate (PBAT) fiber and hydrophilic modification.

This paper demonstrates that melt centrifugal spinning could be used to effectively fabricate degradable poly (butylene adipate-co-terephthalate) (PBAT) fibers with uniform fiber diameter. The hydrophobic PBAT fibers were modified into hydrophilic fibers using the hyperbranched polyesters (HBP) with three-dimensional molecular chain structures and a large number of functional groups at the chain ends. The structures and properties of the obtained fibers were characterized with SEM, XRD, DSC, contact angle, and tensile strength analyses. Results indicate that fibers with uniform diameters can be conveniently fabricated by designing a spinneret. The obtained fibers showed no apparent change in crystallization compared to PBAT pellets, while the thermal stability and mechanical properties of PBAT/HBP fibers were dependent on the HBP ratio in fibers. More importantly, the obtained fibers gradually changed from hydrophobic to super-hydrophilic with increasing HBP content in fibers up to 30%. The modified hydrophilic PBAT/HBP presents a greatly significant potential for application in biomedical fields.

Electrospinning preparation and spectral characterizations of the inclusion complex of ferulic acid and γ-cyclodextrin with encapsulation into polyvinyl alcohol electrospun nanofibers

In the present work, the inclusion complex of γ-Cyclodextrin (D) and Ferulic acid (FA) (D/FA) was encapsulated into Polyvinyl Alcohol (PVA) to form electrospun nanofibers by electrospinning under optimal condition. The structural and thermal characteristics of PVA, PVA/FA, PVA/D/FA andpure powder of FA were investigated by FT-IR, UV, 1H NMR. Smooth with uniform morphology and fiber diameter distributions were indicated by Scanning Electron Microscopy (SEM). Moreover,PVA, PVA/FA, PVA/D/FA nanofibers thermal behavior were investigated by TGA and DSC analysis. That result suggests that the thermal stability of PVA/D/FA nanofibers was enhanced due to inclusion complexation. Besides, the releasing rate of FA from the PVA nanofibers was measured by the calibration graph.A theoretical study of the γ-CD/FA inclusion complex was obtained by using Gaussian’s software, which gives good results with FT-IR and UV data.This study investigated the significant development of biobased polymeric nanofibers for active food packaging applications.

Liquid Water Transport Behavior at GDL-Channel Interface of a Wave-Like Channel

This paper evaluates the liquid water at the gas diffusion layer-channel (GDL-channel) interface of reconstructed GDL microstructures with uniform and non-uniform fiber diameters in wave-like channels. A non-uniform GDL microstructure is reconstructed for the first time at the GDL-channel interface to evaluate droplet motion. The three-layer GDL microstructures are generated using the stochastic technique and implemented using the OpenFOAM computational fluid dynamics (CFD) software (OpenFOAM-6, OpenFOAM Foundation Ltd., London, UK). The present study considers the relationship between reconstructed GDL surfaces with varying fiber diameters, wettability, superficial inlet velocity and droplet size. Results show that the droplet detachment and the average droplet velocity decrease with an increase in the fiber diameter as well as the structural arrangement of the fibers. Under the non-uniform fiber arrangement, the removal rate of water droplets is not significantly improved. However, the choice of smaller fiber diameters facilitates the transport of droplets, as hydrophobicity increases even at slight surface roughness. The results also indicate that the average droplet velocity decreases under low inlet velocity conditions while increasing under high inlet velocity conditions. Therefore, the structural make-up of the GDL-channel interface influences the droplet dynamics, and the implementation of a non-uniform GDL structure should also be considered in the GDL designs.

Double stimuli-responsive cellulose nanocrystals reinforced electrospun PHBV composites membrane for intelligent drug release

Double stimuli-responsive functionalized cellulose nanocrystal-poly[2-(dimethylamino)ethyl methacrylate] (CNC-g-PDMAEMA) reinforced poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) electrospun composite membranes were explored as drug delivery vehicles using tetracycline hydrochloride (TH) as a model drug. It was found that rigid CNC-g-PDMAEMA nanoparticles enhanced thermal, crystallization and hydrophilic properties of PHBV. Moreover, great improvements in fiber diameter uniformity, crystallization ability and maximum decomposition temperature (Tmax) could be achieved at 6 wt% CNC-g-PDMAEMA. Furthermore, by introducing stimuli-responsive CNC-g-PDMAEMA nanofillers, intelligent and long-term sustained release behavior of composite membranes could be achieved. The releasing mechanism of composite membranes based on zero order, first order, Higuchi and Korsmeyere-Peppas mathematical models was clearly demonstrated, giving effective technical guidance for practical drug delivery systems.

Effect of process parameters on additive-free electrospinning of regenerated silk fibroin nonwovens

Silk fibroin is a biomaterial with multiple beneficial properties for use in regenerative medicine and tissue engineering. When dissolving and processing the reconstituted silk fibroin solution by electrospinning, the arrangement and size of fibers can be manifold varied and according fiber diameters reduced to the nanometer range. Such nonwovens show high porosity as well as potential biocompatibility. Usually, electrospinning of most biomaterials demands for the application of additives, which enable stable electrospinning by adjusting viscosity, and are intended to evaporate during processing or to be washed out afterwards. However, the use of such additives increases costs and has to be taken into account in terms of biological risks when used for biomedical applications.In this study, we explored the possibilities of additive-free electrospinning of pure fibroin nonwovens and tried to optimize process parameters to enable stable processing. We used natural silk derived from the mulberry silkworm Bombyx mori. After degumming, the silk fibroin was dissolved and the viscosity of the spinning solution was controlled by partial evaporation of the initial solving agent. This way, we were able to completely avoid the use of additives and manufacture nonwovens, which potentially offer higher biocompatibility and reduced immunogenicity. Temperature and relative humidity during electrospinning were systematically varied (25–35 °C, 25–30% RH). In a second step, the nonwovens optionally underwent methanol treatment to initiate beta-sheet formation in order to increase structural integrity and strength. Comprehensive surface analysis on the different nonwovens was performed using scanning electron microscopy and supplemented by additional mechanical testing. Cytotoxicity was evaluated using BrdU-assay, XTT-assay, LDH-assay and live-dead staining. Our findings were, that an increase of temperature and relative humidity led to unequal fiber diameters and defective nonwovens. Resistance to penetration decreased accordingly. The most uniform fiber diameters of 998 ± 63 nm were obtained at 30 °C and 25% relative humidity, also showing the highest value for resistance to penetration (0.20 N). The according pure fibroin nonwoven also showed no signs of cytotoxicity. However, while the biological response showed statistical evidence, the material characteristics showed no statistically significant correlation to changes of the ambient conditions within the investigated ranges. We suggest that further experiments should explore additional ranges for temperature and humidity and further focus on the repeatability of material properties in dependency of suitable process windows.

Production of Essential Oil-Based Composite Nanofibers by Emulsion Electrospinning

This study aimed to produce polyvinylpyrrolidone (PVP)/gelatin (GEL)/lavender essential oil (LEO)-based nanofibers by means of oil-in-water emulsion electrospinning. Firstly, the polymer solution properties were measured, and then optimization of nanofiber production and characterization of the nanofibrous web were carried out. As gelatin was added to the PVP solution, viscosity was found to increase while surface tension and conductivity decreased. PVP/GEL (50/50) was determined to be the optimum sample in terms of nanoweb quality, fiber diameter, diameter uniformity, and gelatin content. Nanofiber production proceeded with PVP/GEL (50/50) and various concentrations of LEO. FT-IR results confirmed that LEO, PVP, and gelatin were incorporated in the chemical structure of the nanofibers. Generally, ultra-fine and uniform nanofibers were obtained, except when using pure PVP or PVP/GEL (50/50) including 8 wt % LEO. The finest fibers were obtained from PVP/GEL (100/0) (183 nm), and the most uniform fibers were obtained from PVP/GEL (50/50) (fiber diameter uniformity coefficient of 1.04). All nanofiber samples displayed unimodal distribution curves of histograms. While the addition of gelatin affected solution properties and average fiber diameter, the addition of LEO did not affect fiber properties.

Novel Lignin-Cellulose-Based Carbon Nanofibers as High-Performance Supercapacitors.

In this work, a simple phosphating process was proposed to modify cellulose-acetate (CA) and lignin for a novel energy storage precursor material. The prepared precursor fibers exhibited good thermal stability of lignin and flexibility of CA. Subsequently, the precursor fibers undergo a short preoxidation and carbonization treatment process to obtain the biomass-based carbon fibers (CFs) with complete fibrous morphology, uniform fiber diameter, high surface areas, good flexibility, and excellent power storage capacity. The specific capacitance of 346.6 F/g was obtained by using CFs-5 (prepared with 40% H3PO4 content) as a supercapacitor. Simultaneously, the biomass-based CF supercapacitor device delivers a high-energy density of 31.5 Wh/kg at the power density of 400 W/kg. These results indicate that the introduction of H3PO4 can effectively reduce the energy consumption of the preoxidation treatment process for the preparation of the biomass-based CFs, while increasing the energy storage properties significantly. This novel strategy showed a successful route for the preparation of high-quality and low-consumption biomass-based CFs.

Green electrospun nanofiber membranes filter prepared from novel biomass thermoplastic copolyester: Morphologies and filtration properties

Abstract High-performance and eco-friendly nonwoven-nanofiber filters comprising renewably sourced bio-based polyesters were fabricated by electrospinning (ES). Typical commercial nonwoven filters are thick, with uneven fiber distributions and low recovery. Bio-based polymers made of raw plant materials have soft textures. Over 75% of the polyester used herein was sourced renewable. We observed variations in its morphology under different operating conditions in scanning electron microscope images by tuning the operating parameters of ES and using different DMF/CHCl3 solvent ratios. We produced various types of ES nanofibers with uniform fiber diameters ranging from 400 to 2000 nm, which increased filter efficiency and helped overcome existing shortcomings in filter applications. A scanning mobility particle sizer and NaCl aerosol particles of sizes 30–300 nm were used to test the prepared nanofiber filters. Owing to their high specific surface areas/volume ratios and small-fiber diameters, the nanofiber filters with fiber diameters smaller than 500 nm forcefully resisted the majority of suspended particles. The averaged penetration ability of ES fiber was decreased from 30% to 4%, with increasing heating temperature and annealing time. Thicker ES fibers with beaded morphologies exhibited average penetration

Investigation on the Performance Improvement of Polyacrylonitrile-Derived Flexible Electrospun Carbon Nanofiber Mats

Polyacrylonitrile (PAN)-derived carbon nanofiber mats were fabricated using electrospinning and further carbonization. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical characterization were used to investigate the effects of precursor concentration, thermal stabilization and carbonization temperature, addition of multi-walled carbon nanotubes (MWCNTs), activation of nitric acid and sulfuric acid on the morphologies, conductivity, flexibility and electrochemical properties of the fabricated carbon nanofiber mats. The results reveal that the carbon nanofiber mats with uniform fiber diameter of 200 nm and sheet resistance of 154 Ω/sq could be achieved with a PAN mass fraction of 12 wt% and a thermal stabilization and carbonization temperature of 270 °C and 900 °C, respectively. Due to the good conductivity and high strength of the MWCNTs, the sheet resistance of the carbon nanofiber mats decreases to around 60 Ω/sq by adding MWCNTs to precursor, and the mats exhibit excellent bend and fold flexibility. The electrochemical performance of the co-spun carbon nanofiber mats could be further improved by the activation treatment of acids, and the maximum specific capacitance of the carbon mat reaches 113.5 F/g at a current density of 0.1 mA/cm2 in the case of 1:3 HNO3:H2SO4. The investigation provides a reference for improving the performance of spun carbon nanofiber mats, which can be used as the electrodes or current collectors to further load other active materials in the applications of energy storage devices.

Adsorption and dyeing properties of acid dyes on fine denier silk fibers

In this work, the surface morphology and diameter distribution of fine denier silk fiber were observed and measured. The adsorption property of acid orange 7 on the fine denier silk fiber was studied. The pseudo-first-order model and pseudo-second-order model adsorption kinetic models were employed to evaluate the experimental data. The effects of pH values and reaction temperature on the dyeing property were investigated. The results indicated that the fine denier silk fiber exhibited a uniform fiber diameter (9 µm), which is smaller than that of conventional silk fiber (16 µm). The adsorption process of the dye could be described using pseudo-second-order kinetic equations. A higher the amount of dye adsorption at equilibrium and faster adsorption rate was obtained for the fine denier silk fiber. The color strength of fine denier silk fibers was improved for the decreased pH values and increased temperature, which exhibited an excellent dyeing property.