Changes In Fiber Diameter Research Articles

Characterization of Nanoporous Poly(Lactic Acid) Microfibers Using a Simplified Centrifugal Spinning Method

In recent years, great attention has been paid to the development of porous materials with excellent reactivity and absorbency. The poly(lactic acid) (PLA) microfibers with uniform nanopores were successfully prepared by rotary centrifugal spinning using PLA/chloroform solution. Previous research showed that PLA microfibers have extremely high oil absorbing capacity. In this study, the changes in fiber diameter and nanopore diameter of nanoporous PLA microfibers under different fabrication conditions and the adsorption capacity of Prussian blue nanoparticles were systematically evaluated. The results showed that the fiber diameter increased with increasing PLA/chloroform solution concentration. Furthermore, it was found that the amount of adsorbed Prussian blue nanoparticles increased with the increase in fiber diameter. Prussian blue nanoparticles are known to adsorb radioactive materials such as cesium, and are expected to be applied to the recovery of cesium diffused in the atmosphere and ocean.

Development of novel parameters for characterising scale morphology of wool fibre and its correlation with dye diffusion coefficient of acid dye

This paper reports the development of novel surface parameters which can be used to characterise the scale structure of wool fibres obtained from different breeds. Scanning electron microscopy and subsequent image analysis technique were used to study wool fibres from Leicester, Dartmoor, Ryeland and Herdwick breeds of sheep. Novel scale parameters related to wool fibre’s effective chemical diffusion pathway were developed. Namely, the total scale perimeter per 100 µm fibre length and scale perimeter index, which is the total scale perimeter per 100 µm length divided by the fibre diameter. Wool fibres obtained from different breeds showed significant differences in their scale pattern with the change in fibre diameter. The scale perimeter per 100 µm length increased with the fibre diameter and showed a polynomial correlation. It was also demonstrated that an increase in the diameter of the wool fibre resulted in an increase in the apparent dye diffusion coefficient, which contrasts the established theory that finer fibres are associated with a higher dyeing rate. The increase in effective diffusion pathway (total scale perimeter per 100 µm) for the wool fibres (among different breeds) resulted in a higher dye diffusion rate at the initial phase of dyeing (liquor to surface).

Pressure Drop Dynamics during Filtration of Mixture Aerosol Containing Water, Oil, and Soot Particles on Nonwoven Filters.

The pressure drop dynamics during the filtration of three-component mixture aerosols are investigated and compared with two and single-component aerosols. The main area of interest is the effect of the addition of a small quantity of liquid (oil) and solid (soot) particles during the filtration of aerosol containing water mist. In addition, calculations of the change in filter mass during oil aerosol filtration have been carried out and compared with the experimental results. The new, improved filtration efficiency model takes into account a better coefficient fitting in the filtration mechanism equations. The limitations in the change in fibre diameter and packing density resulting from the filter loading have been implemented in the model. Additionally, the calculation model employs the fibre size distribution representation via multiple average fibre diameters. The changes in fibre diameter are dependent on each fibre's calculated filtration efficiency. The improved filtration model has been utilised to predict the mass change of the filters during the filtration of pure and mixture aerosols. The pressure drop calculation model based on changes in filter mass has been formulated. The model is then utilised to calculate pressure drop changes resulting from the filtration of the oil aerosol and water and oil mixture aerosol.

Various mechanical tests of carbon fiber monofilaments

In recent years, in order to accurately predict the mechanical properties of carbon fiber-reinforced plastic by computer-aided engineering, it has become important to understand the mechanical properties of carbon fiber as a reinforcement material. Since carbon fiber is a material whose properties are highly anisotropic, information on tensile properties only in the axial direction of the fiber is not sufficient for predicting composite properties, and tests to obtain properties in various directions are desired. This paper discusses the anisotropy of carbon fibers by presenting the results of our previous tests on carbon fiber monofilaments, including observation of the changes in fiber diameter, dynamic and static torsion tests, torsion-tension tests, transverse crush tests, axial compression tests and three-point bending tests, and finite element method analysis using elastic moduli obtained from these tests.

Mechanical, degradation rate, and antibacterial properties of a collagen-chitosan/PVA composite nanofiber

This study synthesized collagen-chitosan/PVA nanofiber composites using the electrospinning method. Characterizations included Fourier transform infrared spectroscopy (FTIR) and surface morphology using scanning electron microscopy (SEM). Investigations were carried out on tensile strength, degradation rate, and antibacterial test. It was found that the functional groups C–H, –OH, C–O, C–N, and N–H were suitable for PVA, collagen, and chitosan materials. The SEM showed that increasing the PVA composition caused a change in fiber diameter ranging from 34.64 to 71.63 nm. The tensile strength results show that the smallest nanofiber diameter has the highest ultimate strength value of 5.6 ± 0.4 MPa. In addition, it was found that the rate of degradation was directly proportional to the increase in concentration. Antibacterial activity test was carried out using two types of bacteria, namely gram-positive bacteria S. aureus and gram-negative bacteria E. coli. The results showed that the collagen-chitosan/PVA nanofiber composite had a diameter of antibacterial inhibition for E. coli and S. aureus bacteria, respectively.

Temperature and strain sensitivities of surface and hybrid acoustic wave Brillouin scattering in optical microfibers

Temperature and strain sensitivities of surface acoustic wave (SAW) and hybrid acoustic wave (HAW) Brillouin scattering (BS) in 1 μm–1.3 μm diameter optical microfibers are simulated. In contrast to stimulated Brillouin scattering (SBS) from bulk acoustic wave in standard optical fiber, SAW and HAW BS, due to SAWs and HAWs induced by the coupling of longitudinal and shear waves and propagating along the surface and core of microfiber respectively, facilitate innovative detection in optical microfibers sensing. The highest temperature and strain sensitivities of the hybrid acoustic modes (HAMs) are 1.082 MHz/°C and 0.0289 MHz/με, respectively, which is suitable for microfiber sensing application of high temperature and strain resolutions. Meanwhile, the temperature and strain sensitivities of the SAMs are less affected by fiber diameter changes, ranging from 0.05 MHz/°C/μm to 0.25 MHz/°C/μm and 1 × 10−4 MHz/με/μm to 5 × 10−4 MHz/με/μm, respectively. It can be found that that SAW BS for temperature and strain sensing would put less stress on manufacturing constraints for optical microfibers. Besides, the simultaneous sensing of temperature and strain can be realized by SAW and HAW BS, with temperature and strain errors as low as 0.30 °C–0.34 °C and 14.47 με–16.25 με.

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.

Fabrication of electrospun poly(vinyl alcohol) nanofibers loaded with zinc oxide particles

Smooth, continuous, and bead-free zinc oxide (ZnO)-loaded electrospun poly(vinyl alcohol) (PVA) nanofibers were fabricated using 8% and 10% PVA concentration in water. Scanning electron microscope images showed a significant change in fiber diameter upon the addition of ZnO powders. X-ray diffraction and Raman spectral analysis revealed the successful physical blending of ZnO in PVA. Through UV–vis spectroscopy, it was found that the optical bandgap of the ZnO:PVA composite sheets ranged from 3.15 to 3.45 eV. The immobilization of ZnO in PVA support may find use as a reusable material for photocatalytic applications.

Morphological analysis of fibrous webs electrospun from Polycaprolactone, polylactic acid and their blends in chloroform based solvent systems

In this study, polycaprolactone (PCL), polylactic acid (PLA), and PLA/PCL blend electrospun fibrous webs are prepared using chloroform based solvent systems at different concentrations. The solvents to be used with chloroform are selected in accordance with the morphological and rheological structures of the polymers. While the morphology of the produced networks is observed under a scanning electron microscope, fiber diameter measurements and pore analysis are performed with Image J Software System. Although bead-free webs could not be achieved for neat PCL samples, neat PLA samples and PCL/PLA blends result in smooth fiber surfaces with homogeneous fiber diameter distributions. The results show that the increase in PLA concentration does not cause much change in fiber diameter but induces an increase in the area of pores. Furthermore, in the PLA/PCL blend, it is determined that as the ratio of PCL in the mixture increases, the fiber diameter decreases even if there is an acceptable reduction in the average pore area.

Generation of desminopathy in rats using CRISPR-Cas9.

BackgroundDesminopathy is a clinically heterogeneous muscle disease caused by over 60 different mutations in desmin. The most common mutation with a clinical phenotype in humans is an exchange of arginine to proline at position 350 of desmin leading to p.R350P. We created the first CRISPR‐Cas9 engineered rat model for a muscle disease by mirroring the R350P mutation in humans.MethodsUsing CRISPR‐Cas9 technology, Des c.1045‐1046 (AGG > CCG) was introduced into exon 6 of the rat genome causing p.R349P. The genotype of each animal was confirmed via quantitative PCR. Six male rats with a mutation in desmin (n = 6) between the age of 120–150 days and an equal number of wild type littermates (n = 6) were used for experiments. Maximal plantar flexion force was measured in vivo and combined with the collection of muscle weights, immunoblotting, and histological analysis. In addition to the baseline phenotyping, we performed a synergist ablation study in the same animals.ResultsWe found a difference in the number of central nuclei between desmin mutants (1 ± 0.4%) and wild type littermates (0.2 ± 0.1%; P < 0.05). While muscle weights did not differ, we found the levels of many structural proteins to be altered in mutant animals. Dystrophin and syntrophin were increased 54% and 45% in desmin mutants, respectively (P < 0.05). Dysferlin and Annexin A2, proteins associated with membrane repair, were increased two‐fold and 32%, respectively, in mutants (P < 0.05). Synergist ablation caused similar increases in muscle weight between mutant and wild type animals, but changes in fibre diameter revealed that fibre hypertrophy in desmin mutants was hampered compared with wild type animals (P < 0.05).ConclusionsWe created a novel animal model for desminopathy that will be a useful tool in furthering our understanding of the disease. While mutant animals at an age corresponding to a preclinical age in humans show no macroscopic differences, microscopic and molecular changes are already present. Future studies should aim to further decipher those biological changes that precede the clinical progression of disease and test therapeutic approaches to delay disease progression.

Halochromic Polystyrene Nanofibers Obtained by Solution Blow Spinning for Wine pH Sensing.

Colorimetric sensors developed by the solution blow spinning (SBS) technique have a rapid response to a variation in different physicochemical properties. In this study, polystyrene nanofibrous (PSNF) mats containing the bromothymol blue (BTB) indicator were obtained by SBS for the pH sensing of wine sample. The incorporation of the indicator did not promote changes in fiber diameter but led to the appearance of beads, allowing for the encapsulation of BTB. The halochromic property of BTB was retained in the PSNF material, and the migration tests showed that the indicator mats presented values below the maximum acceptable limit (10 mg dm−2) established by EU Commission Regulation No. 10/2011 for foods with an alcohol content up to 20%. The present study opens the possibility of applying nanostructured materials to innovative food packaging which, through nanosensory zones, change color as a function of the food pH.

Development of Coaxial Air-blown Electrospinning Process for Manufacturing Non-woven Nanofiber. II. Intelligent Modeling

This study describes the development of an electro-coaxial air-blown spinning system, using a sheath-core type nozzle and an intelligent model for predicting the morphological changes induced by varying four process parameters. We prepared 65 samples with different parametric conditions and analyzed their characteristics. We could confirm that the mean fiber diameter decreased with increase in the air flow rate and voltage, and increased with an increase in the solution concentration. A too short tip-to-collector distance (TCD) resulted in flat and thick fiber deposition, and no changes in fiber diameter were observed beyond a specific TCD value. Based on experimentally measured morphological data, we could establish an intelligent prediction model with four inputs (air flow rate, solution concentration, applied voltage, and TCD) and one output (mean fiber diameter). The simple linear regression analysis model and multiple linear regression analysis model were found to yield mean squared error (MSE) values too high to be used as predictive models. The neural network training model and fuzzy logic model were confirmed to have low MSE values. Among the three prediction models, the neural network training model was confirmed to have the smallest error between the experimental and predicted values. The results of the analysis of the BET specific surface area confirmed the same tendencies as those shown by the image analysis results, which allowed us to conclude that electrospinning using a coaxial air-blown nozzle can enhance the performance of nonwoven nanofibers.

Simulation of performance of fibrous filter media composed of cellulose and synthetic fibers

Fibrous filter media with reticular support structure and tortuous pore channels have been widely used in filtration fields. Most of these filter media contain multiple types of fibers such as wood pulp fibers, glass fibers or synthetic fibers with a broad range of diameters to meet the requirements of filtration and strength performance. Some fibers in the filter media, e.g. cellulose fibers, have complex and irregular shapes such as hollow structure. It is necessary to generate a more realistic filter media model based on the actual properties of fibers. In this work, fibrous filter media with complex microstructure were investigated by simulation method. SEM (scanning electron microscope) and fiber analyzer were used to obtain the physical characteristics of fiber such as diameter, wall thickness, length Gaussian distributions, and cross-section shape. Based on these experimental data, a database containing several common fiber models was created. 3-D fibrous models corresponding to the real wet-laid binderless filter media were generated. Average pore size, permeability and collection efficiency simulations were carried out using the modules of the GeoDict code. The simulated results were close to the experimental data. With the work of this study, it was found that smaller diameter PET fibers in the filter media led to a lower average pore size, lower permeability and a better collection performance. When the diameter of PET fibers was < 5.54 μm, the change in fiber diameter has a great impact on the performance. When the diameter of PET fibers was larger than 12.40 μm, it has less effect on the performance.

The carbonization of polyacrylonitrile-derived electrospun carbon nanofibers studied by in situ transmission electron microscopy.

Cathode structures derived from carbonized electrospun polyacrylonitrile (PAN) nanofibers are a current line of development for improvement of gas diffusion electrodes for metal–air batteries and fuel cells. Diameter, surface morphology, carbon structure and chemical composition of the carbon based fibers play a crucial role for the functionality of the resulting cathodes, especially with respect to oxygen adsorption properties, electrolyte wetting and electronic conductivity. These functionalities of the carbon fibers are strongly influenced by the carbonization process. Hitherto, fibers were mostly characterized by ex situ methods, which require great effort for statistical analysis in the case of microscopy. Here, we show the morphological and structural evolution of nanofibers during their carbonization at up to 1000 °C by in situ transmission electron microscopy (TEM). Changes in fiber diameter and surface morphology of individual nanofibers were observed at 250 °C, 600 °C, 800 °C and 1000 °C in imaging mode. The structural evolution was studied by concomitant high resolution TEM and electron diffraction. The results show with comparatively little effort shrinkage of the nanofiber diameter, roughening of the surface morphology and formation of turbostratic carbon with increasing carbonization temperature at identical locations.

Investigation of Protective Coatings for Carbon Fibers by the Sol-Gel Method

The article shows the possibility of applying a silicon dioxide coating on the carbon fiber by the sol-gel method. The evaluation of the protective properties of the obtained coatings at a temperature of 600 ° C is given; the changing of the a coated fiber surface morphology during the destruction process is shown for the first time. The destruction of the carbon fiber surface without coating begins at a soaking time of 120 min, which is accompanied by a significant decrease in the diameter of the fiber. The destruction of the coated carbon fiber surface begins at a soaking time of 360 minutes, the fiber diameter changes insignificantly. The paper shows that the sol-gel coatings slow down the oxidation of the carbon fiber more than 2 times.

Dimension-Based Design of Melt Electrowritten Scaffolds.

The electrohydrodynamic stabilization of direct-written fluid jets is explored to design and manufacture tissue engineering scaffolds based on their desired fiber dimensions. It is demonstrated that melt electrowriting can fabricate a full spectrum of various fibers with discrete diameters (2-50 µm) using a single nozzle. This change in fiber diameter is digitally controlled by combining the mass flow rate to the nozzle with collector speed variations without changing the applied voltage. The greatest spectrum of fiber diameters was achieved by the simultaneous alteration of those parameters during printing. The highest placement accuracy could be achieved when maintaining the collector speed slightly above the critical translation speed. This permits the fabrication of medical-grade poly(ε-caprolactone) into complex multimodal and multiphasic scaffolds, using a single nozzle in a single print. This ability to control fiber diameter during printing opens new design opportunities for accurate scaffold fabrication for biomedical applications.

Extraction process optimization of Juncus plant fibers for its use in a green composite

In the context of the development of green building materials using plant fibers, this research has focused on the characterization of natural fibers extracted from Juncus plant, commonly called Juncus. A well-known chemical extraction method was applied here for the first time at our knowledge to the Juncus plant, in order to obtain better mechanical characteristics (tensile strength and elastic modulus) and better surface morphology. Therefore, a chemical treatment with alkalization through various factors such as temperature, NaOH concentration (alkalizing agent), presence or not of sodium dithionite Na2S2O4 (for reducing lignin) and sodium hypochlorite NaOCl (chlorine bleach delignification agent) was performed. This study aims to determine the effects of different chemical treatments applied to the fiber extraction of Juncus stem, on the change in fiber diameter, surface state morphology, density, tensile strength and elastic modulus. As one of the Juncus fiber treatments considered in this work, the cold alkali-treatment did not give good results in terms of delignification of the Juncus fibers (There is always non-cellulosic products on the treated fiber) and low values of tensile stress and modulus of elasticity. The treatment with a solution of 8% NaOH, sodium hypochlorite and sodium dithionite at hot temperature present the best result due to the effective delignification of the fibers which has allowed reaching highest tensile strength and highest elastic modulus.

The effect of engineered nanotopography of electrospun microfibers on fiber rigidity and macrophage cytokine production

Currently, it is unknown how the mechanical properties of electrospun fibers, and the presentation of surface nanotopography influence macrophage gene expression and protein production. By further elucidating how specific fiber properties (mechanical properties or surface properties) alter macrophage behavior, it may be possible to create electrospun fiber scaffolds capable of initiating unique cellular and tissue responses. In this study, we determined the elastic modulus and rigidity of fibers with varying topographies created by finely controlling humidity and including a non-solvent during electrospinning. In total,five fiber scaffold types were produced. Analysis of fiber physical properties demonstrated no change in fiber diameter amongst the five different fiber groups. However, the four different fibrous scaffolds with nanopits or divots each possessed different numbers of pits with different nanoscale dimensions. Unpolarized bone marrow derived murine macrophages (M0), macrophages polarized towards a pro-inflammatory phenotype (M1), or macrophages polarized towards anti-inflammatory phenotype (M2b) were placed onto each of the scaffolds and cytokine RNA expression and protein production were analyzed. Specific nanotopographies did not appreciably alter cytokine production from undifferentiated macrophages (M0) or anti-inflammatory macrophages (M2b), but a specific fiber (with many small pits) did increase IL-12 transcript and IL-12 protein production compared to fibers with small divots. When analyzing the mechanical properties between fibers with divots or with many small pits,divoted fibers possessed similar elastic moduli but different stiffness values. In total,we present techniques capable of creating unique electrospun fibers. These unique fibers have varying fiber mechanical characteristics and modestly modulate macrophage cytokine expression.

Essential oil loaded electrospun membrane - A potential sprout supressant

Quality of the potato tubers during storage could be retained by efficient sprout controlling. Recently it has become important to use natural anti-sprouting agents such as essential oils (EO) as well as pure compounds derived from essential oils. Therefore, in the present work we have attempted to explore the anti-sprouting efficiency of peppermint essential oil (Peppermint EO) loaded Polyurethane (PU)/ Polymethylmethacrylate (PMMA) ultra-thin fibrous mats during the post harvest storage of potato tubers. PU/PMMA blend fibers were produced by electrospinning technique. The electrospun fiber mats were loaded with 2 wt% peppermint essential oil. Essential oil loaded and unloaded fibers were characterised for its chemical composition, surface morphology and controlled release of Peppermint EO using Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and UV-Vis spectrophotometer. The SEM results revealed the change in fiber diameter before and after loading. In-vitro release of Peppermint EO in ethanol was approximately found to be 84.8%. Storage life of potato tubers in the presence of peppermint oil was assessed. Storage life study concluded that tubers stored with peppermint EO loaded fibers showed no sprout development for 30 days due to controlled release of EO whereas the tubers with unloaded mats sprouted in 10 days. Thus, the fabricated peppermint EO loaded PU/PMMA fibrous membrane having an excellent anti-sprouting property would be a potential candidate for the post harvest storage of potatoes.

Electrically conductive gel/fibers composite scaffold with graded properties

Gradient biomaterials have emerged as fascinating platforms to satisfy the need for imitation of ubiquitous gradients in biology, especially those found at tissue interfaces. In the current study, a gradient fiber-hydrogel scaffold was fabricated to imitate the extracellular matrix of soft-to-hard tissue interfaces. For the fiber proportion, a gradient electrospinning was developed where controlled mixing of solutions with dissimilar concentration of a conductive polymer in injection vessel imparted a composition gradient to electrospinning jet, and thus electrospun fibers. The planar graded fibers were exposed to ultrasound to be three-dimensional and gel permeable. For the hydrogel fraction, a gradient mixing tool was used in which controlled mixing of solutions with disparate concentration of hydrogel components conferred a composition gradient to hydrogel precursor solution. The graded precursor solution was introduced to gradient 3D fibers and then self-crosslinked. Gradient fibers, hydrogel and fiber-gel composite were assessed by many techniques including microscopy, spectroscopy, mechanical analysis and conductivity measurement to ascertain gradient formation. Polymeric constituents' gradient in electrospinning outflow gave rise to not only gradual changes in fiber diameter, also subtle variations in electrical conductivity and other fibers' attributes. Gradient hydrogel making apparatus rendered a steady increase in crosslink involving component and yielded a hydrogel with graded features. The created composite revealed the propitious unification of fibrous and gelation parts into a single scaffold with no detrimental effect on structure and gradient of each part.