Fibers Of Different Diameters Research Articles

Composite suture material based on polylactide accelerates the healing of surgical wounds in in vivo experiment.

In laboratory conditions, composite sutures based on polylactide (PLA) containing chitin nanofibrils modified with polyethylene glycol (CN-PEG) and poviargol (silver nanoparticles stabilized with poly(N-vinylpyrrolidone)) were obtained, studied, and used as a prototype. Surgical sutures threads with the addition of CN-PEG have stable mechanical properties both in air and in a buffer simulating the environment of a living organism. The yield strength of oriented threads decreased by an average of 15%, whereas for non-oriented threads the decrease was 3-4 times. The strength values in simple units of unfilled PLA, PLA containing 5 wt % CN-PEG, and PLA with 1 wt % Poviargol were on average 50% higher than the national standard 31620-2012. The results of in vivo experiments on albino rats (cross-linking skin and muscle tissue in the linea alba area) showed that composite sutures are best for suturing muscle tissue, whereas unfilled PLA sutures are more suitable for suturing skin. When suturing muscle tissue, suturing with composite sutures increased the number of collagen fibers of different diameters.

Femtosecond laser writing of fiber Bragg gratings using the phase mask technique: a geometrical optics analysis based on the Bravais refractive index

Material modification is produced inside silica-based optical fibers of different diameters using tightly focused near-infrared (central wavelength at 800 nm) femtosecond laser pulses and the phase mask technique which is often employed for laser inscription of fiber Bragg gratings. 1st-, 2nd-, and 3rd-order phase masks designed for the operation at 800 nm are used in the experiments. The inscription is performed at different distances from the fiber’s front surface by translating the focusing cylindrical lens along the laser beam propagation direction. The results show that the material modification produced by means of the 2nd- and 3rd-order phase mask can be positioned at any predetermined distance from the fiber’s front surface. In contrast, when the 1st-order mask is used for laser writing, the maximum distance from the fiber’s front surface at which material modification can be produced is limited and determined by three main parameters: the diffraction angle of the phase mask, the refractive index of the fiber and the diameter of the fiber.

Aligned electrospun fibers of different diameters for improving cell migration capacity

Electrospun fibers have gained significant attention as scaffolds in skin tissue engineering due to their biomimetic properties, which resemble the fibrous extracellular matrix. The morphological characteristics of electrospun fibers play a crucial role in determining cell behavior. However, the effects of electrospun fibers’ arrangement and diameters on human skin fibroblasts (HSFs) remain elusive. Here, we revealed the impact of electrospun fiber diameters (700 nm, 2000 nm, and 3000 nm) on HSFs' proliferation, migration, and functional expression. The results demonstrated that all fibers exhibited good cytocompatibility. HSFs cultured on nanofibers (700 nm diameter) displayed a more dispersed and elongated morphology. Conversely, fibers with a diameter of 3000 nm exhibited a reduced specific surface area and lower adsorption of adhesion proteins, resulting in enhanced cell migration speed and effective migration rate. Meanwhile, the expression levels of migration-related genes and proteins were upregulated at 48 h for the 3000 nm fibers. This study demonstrated the unique role of fiber diameters in controlling the physiological functions of cells, especially decision-making and navigating migration in complex microenvironments of aligned electrospun fibers, and highlights the utility of these bioactive substitutes in skin tissue engineering applications.

Thulium fiber laser vs Ho:YAG in RIRS: a prospective randomized clinical trial assessing the efficacy of lasers and different fiber diameters (150 µm and 200 µm)

IntroductionThe aims of the study: (1) to compare the Super Pulse Thulium Fiber Laser (SP TFL) and the holmium: yttrium–aluminium-garnet (Ho:YAG) lasers in retrograde intrarenal surgery (RIRS); (2) to compare the efficacy of SP TFL laser fibers of different diameters (150 μm and 200 μm).MethodsA prospective randomized single-blinded trial was conducted. Patients with stones from 10 to 20 mm were randomly assigned RIRS in three groups: (1) SP TFL (NTO IRE-Polus, Russia) with fiber diameter of 150 μm; (2) SP TFL with 200-μm fiber; and (3) Ho:YAG (Lumenis, USA) with 200-μm fiber.ResultsNinety-six patients with kidney stones were randomized to undergo RIRS with SP TFL using a 150-μm fiber (34 patients) and a 200-μm fiber (32 patients) and RIRS with Ho:YAG (30 patients). The median laser on time (LOT) in the 200-μm SP TFL group was 9.2 (6.2–14.6) min, in 150-μm SP TFL—11.4 (7.7–14.9) min (p = 0.390), in Ho:YAG—14.1 (10.8–18.1) min (p = 0.021). The total energy consumed in 200-μm SP TFL was 8.4 (5.8–15.2) kJ; 150-μm SP TFL − 10.8 (7.3–13.5) kJ (p = 0.626) and in Ho:YAG—15.2 (11.1–25.3) kJ (p = 0.005).ConclusionsIrrespective of the density, RIRS with SP TFL laser has proven to be both a safe and effective procedure. Whilst the introduction of smaller fibers may have the potential to reduce the duration of surgery, SP TFL results in a reduction in the LOT and total energy for stone ablation in RIRS compared with Ho:YAG.

Design of parallel double-chain fibrous electrode using electrospinning technique for vanadium redox flow battery with boosted performance

This article proposes a parallel double-chain fibrous electrode structure with dual fibers of different diameters by electrospinning technique for vanadium redox flow battery to improve the battery performance. The larger diameter fibers contribute to the formation of larger pores, enhancing electrolyte flow and mass transfer. Meanwhile, the smaller diameter fibers provide abundant reaction sites. Different fiber diameters are fabricated by using precursor solutions with different concentration ratios. For a single concentration ratio electrode, as the concentration of PAN (Polyacrylonitrile) solution in syringe A increases, the performance of the battery significantly improves. The best performance is achieved by employing a concentration ratio of 20%:10%, i.e., ECF (Electrospun Carbon Fibers)-20%/10% electrode, at various current densities due to largest pore diameter and enough reaction sites. At current densities of 100 mA cm−2 and 200 mA cm−2, the ECF-20%/10% electrode achieves energy efficiencies of 88% and 80.5%, which are twice the energy efficiency of traditional carbon felt electrodes. Moreover, after 200 cycles, the battery capacity decay of ECF-20%/10% electrode only is 27.5%, which is 20.3% lower than that of the carbon felt electrode after 100 cycles. Dual concentration ratio electrode is also fabricated and found to show lower performance than the best single concentration ratio electrode for the reason that the second fabrication stage decreases the pore sizes.

Development of an affordable extrusion 3D bioprinter equipped with a temperature-controlled printhead

Bioprinters show great promise as enablers of regenerative medicine and other biomedical engineering applications. In this work, we present a flexible and cost-effective design for a do-it-yourself bioprinter capable of printing/bioprinting gelatin methacryloyl (GelMA) and Pluronic constructs at flow rates of 0.05–0.1 mL/min and effective resolutions of 500–700 μm. The most distinctive feature of this bioprinter is its ability to control the rheology of bioinks simply by adjusting the extrusion temperature during printing. This is achieved by circulating temperature-controlled water within the printhead, which is engineered as a single 3D-printed component consisting of a water-recirculation jacket surrounding the ink/bioink cartridge. The flexibility to circulate either warm or cold water allows the system to be adapted according to the needs dictated by the bioink composition. Herein, we demonstrate the ability to control the printability of GelMA or Pluronic fibers by decreasing or increasing the temperature, respectively, thereby regulating its viscosity. In addition, any commercial needle with a Luer lock can be incorporated into the printhead, allowing the easy fabrication of fibers of different diameters with a single printhead. We showed that our bioprinter is capable of printing simple 2D constructs with high fidelity (i.e., lines of GelMA with a thickness of ~522 ± 36.83 μm can be printed at linear speeds of 100 mm min−1) and 3D constructs composed of as many as five layers of cell-laden 5% GelMA. We also demonstrated that C2C12 cells bioprinted through needle tips (300 μm in diameter) exhibit adequate post-printing viability (~90%), as well as spreading after 7 days of culture. The presentation of this bioprinter may contribute appreciably to the expansion of bioprinter use due to its low overall cost of manufacture, flexibility and open-source character, amenability to modification and adaptation for use with different 3D-printed printheads, and ability to bioprint using GelMA.

Improved sensitivity of liquid sensing melt-spun polymer fibers filled with carbon nanoparticles by considering solvent-polymer solubility parameters

The Hansen Solubility Parameters (HSPs) and the Relative Energy Differences (REDs) were used to select suitable polymers to perform sensing experiments of electrically conductive nanocomposites against different solvents to employ such materials for sensor applications. From the solvent-polymer HSPs and their REDs, it was determined that polycarbonate (PC) is a polymer with potential towards high liquid sensitivity for different organic solvents. Furthermore, PC is spinnable and sensing fibers of different diameters can be easily produced. In order to get electrically conductive materials, PC was melt-mixed with carbon nanoparticles such as Multi-walled Carbon Nanotubes (MW) and Carbon Black (CB). The materials were then spun into fibers via melt-spinning and evaluated for liquid sensing. It was found that combining MW and CB (50/50 wt%) improved the fiber spinnability and their sensing range in comparison to fibers made of PC and only MW. Liquid sensing evaluations showed that knowing the REDs in advance allows predictions on the ability of nanocomposite fibers to be highly sensitive to specific solvents. From the sensing evaluations it was found that fibers made with hybrid fillers of CB+MW, drawing down ratios of 4 to 12 and filler contents between 3 and 6 wt% showed the best liquid sensing abilities. Depending on the composition and the conditions of fiber production, the maximum values of relative resistance change for fibers with CB+MW were always higher than for fibers containing MW only. Testing for instance butyl acetate as solvent, the fibers with MW+CB achieved values between 600%–3200% for long immersion times, while values between 390 and 1200% were obtained for the fibers with only MW. Testing a selected fiber under a simulated leakage scenario and as sheath/core bi-component fiber showed the effectiveness of these fibers working as liquid detector as well as potential for applications beyond single component fiber sensors.

Сжимаемость композиционных материалов на основе волокнистого наполнителя различного состава

The compressibility of composite materials obtained by impregnation with water dispersion of polyurethane of webs made of polyethylene terephthalate fibers with a diameter of 20 µm and a mixture of these fibers with polyethylene terephthalate fibers with a diameter of 42 µm is investigated. The influence of the composition on the formation of the structure of canvases and composite materials based on them is shown. In the process of heat treatment, the volume of webs made of fibers with a diameter of 20 µm increases and decreases for webs based on a mixture of fibers of different diameters. Compared with canvases, with a degree of impregnation less than 1.0, the water permeability of materials of various compositions increases by 1.5 – 2.0 times. A model is proposed to predict the degree of compressibility of composite materials from the degree of impregnation and load. It is established that compressibility of composite materials decreases when using a web as a fibrous filler in which the fibers are oriented perpendicular to the surface of the web. Less effective for reducing compressibility is the use of a web made of a mixture of fibers of different diameters as a fibrous filler.

Optical Loss in Copper-Coated Multimode Optical Fibers of Different Diameters

Optical Loss in Copper-Coated Multimode Optical Fibers of Different Diameters

Influence of fibres diameter on the AC and DC magnetic characteristics of Fe/Fe3O4 fibres based soft magnetic composites

Fibres-based soft magnetic composites (FSMCs) have been prepared by using Fe fibres of different diameters (65, 125, 250 and 500 μm). The Fe fibres were coated with a 3 μm thick layer of Fe3O4 via the blackening process and subsequently compacted at 700 MPa. The X-ray diffraction analysis (XRD) was used to prove the formation of the Fe3O4 coating on the surface of the fibres. The thickness and the uniformity of the coating were analysed via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The DC measurements performed on the composite cores revealed that the saturation induction increase from 1.36 to 1.68 T, the maximum relative permeability increase from 550 to 940, and the coercive field decrease from 796 to 454 A/m as the fibre's diameter increase from 65 to 500 μm. By using thinner fibres (65 and 125 μm), composites with low losses and stable initial relative permeability, in the frequency range 50 Hz–10 kHz, can be obtained. To distinguish between different types of losses dissipated by our compacts, and the influence of the fibre's diameter on the different components of the total losses, a numerical model for loss separation is proposed. The comparative evolution of the AC magnetic characteristics of the FSMCs and powder-based SMCs is presented. According to the presented results, this new type of composites can be successfully used to prepare magnetic cores designated to work in the medium to high-frequency range.

Hydrogels with Cell Adhesion Peptide-Decorated Channel Walls for Cell Guidance.

A method is reported for making hollow channels within hydrogels decorated with cell-adhesion peptides exclusively at the channel surface. Sacrificial fibers of different diameters are used to introduce channels within poly(ethylene glycol) hydrogels crosslinked with maleimide-thiol chemistry, which are backfilled with a cysteine-containing peptide solution which is conjugated to the lumen with good spatial efficiency. This allows for peptide patterning in only the areas of the hydrogel where they are needed when used as cell-guides, reducing the amount of required peptide 20-fold when compared to bulk functionalization. The power of this approach is highlighted by successfully using these patterned hydrogels without active perfusion to guide fibroblasts and olfactory ensheathing cells-the latter having unique potential in neural repair therapies.

Modelling the effects of ephaptic coupling on selectivity and response patterns during artificial stimulation of peripheral nerves.

Artificial electrical stimulation of peripheral nerves for sensory feedback restoration can greatly benefit from computational models for simulation-based neural implant design in order to reduce the trial-and-error approach usually taken, thus potentially significantly reducing research and development costs and time. To this end, we built a computational model of a peripheral nerve trunk in which the interstitial space between the fibers and the tissues was modelled using a resistor network, thus enabling distance-dependent ephaptic coupling between myelinated axons and between fascicles as well. We used the model to simulate a) the stimulation of a nerve trunk model with a cuff electrode, and b) the propagation of action potentials along the axons. Results were used to investigate the effect of ephaptic interactions on recruitment and selectivity stemming from artificial (i.e., neural implant) stimulation and on the relative timing between action potentials during propagation. Ephaptic coupling was found to increase the number of fibers that are activated by artificial stimulation, thus reducing the artificial currents required for axonal recruitment, and it was found to reduce and shift the range of optimal stimulation amplitudes for maximum inter-fascicular selectivity. During propagation, while fibers of similar diameters tended to lock their action potentials and reduce their conduction velocities, as expected from previous knowledge on bundles of identical axons, the presence of many other fibers of different diameters was found to make their interactions weaker and unstable.

Effect of engineered PLGA‐gelatin‐chitosan/PLGA‐gelatin/PLGA‐gelatin‐graphene three‐layer scaffold on adhesion/proliferation of HUVECs

A three‐layered fibrous scaffold composed of fibers of different diameters in each layer was fabricated in correspondence with the structure of the blood vessels. Effect of solution and electrospinning parameters on morphology and diameters of the fibers were investigated by scanning electron microscopy (SEM), for each layer. The SEM images showed that 18% poly (lactic‐co‐glycolic acid) (PLGA)‐gelatin‐chitosan in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP)/acid acetic solution resulted in bead‐free fibers for the outer layer. For the middle layer, 18% PLGA‐gelatin in HFIP at 13 kV with 13 cm needle to collector distance was chosen as the optimum condition. SEM imaging demonstrated that by increasing graphene content from 0.5 to 2 wt% in the inner layer (as an electrically conductive/platelet anti‐adhesion material), the fiber diameter decreased from 324.01 ± 58.90 to 288.59 ± 70.77 nm. The effect of gelatin crosslinking on the microstructure of the fibers was also examined. Shrinkage ratio decreased from 57 to below 21% upon crosslinking of the three‐layered scaffold in exposure to vapor of 50% glutaraldehyde solution for 2 hours. Mechanical test showed that tensile strength of the crosslinked three‐layer scaffold in the longitudinal direction was 2.90 MPa which is comparable to that of the vein and artery. The MTT [3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide] assay displayed cell viability of above 96% for the PLGA‐gelatin containing 2 wt% graphene. SEM analysis revealed that the addition of graphene to PLGA‐gelatin (up to 2%) causes a remarkable improvement in cell adhesion.

Twist–coil coupling fibres for high stroke tensile artificial muscles

A new concept for tensile artificial muscles is introduced in which the torsional actuation of a twisted polymer fibre drives a twist to writhe conversion in a serially attached elastomeric fibre. Thermally induced torsional rotation of the twisted fibre caused formation of coils in the elastomeric fibre which resulted in overall muscle length contraction. Theoretical predictions of the muscle strain were developed by means of a modified single-helix theory. Experimental tests were conducted to measure the isotonic contraction strains for elastomeric fibres of different diameters and lengths. A good agreement between the measured and calculated results was found. Practical applicability of this muscle is evaluated by using different mechanical loading conditions. Actuation contraction strains as high as 10% were observed with excellent reversibility. Unlike original coiled fibre tensile actuators, these twist-coil artificial muscles did not require any pre-conditioning cycles.

A finite deformation continuum modelling framework for curvature effects in fibre-reinforced nanocomposites

Motivated by experimental findings on one-dimensional nano-materials, this contribution focusses on the elaboration of a fibre curvature based higher-order gradient contribution to the stored energy function in a finite deformation setting. The presented approach is based on the fundamental theoretical developments for fibre-reinforced composites presented by Spencer and Soldatos (2007), which take into account the fibre-bending stiffness in addition to the directional dependency induced by the fibres. A mixed-type finite element formulation is then used for the solution of the resulting system of coupled partial differential equations. A specific form of the stored energy function is introduced such that well-interpretable contributions to the stress- and the couple stress tensor are obtained. It is shown that this framework may, in principle, account for fibres of different diameters and induces a natural length scale into the model. Such continuum theory covering size-effects is of special interest since experiments for different materials suggest significant size-effects at small length scales.

Fabrication of micro-gelatin fiber utilizing coacervation method

Biotechnology has drastically been advanced by the development of iPS and ES cells, which are representative forms induced pluripotent stem cells. In the micro/nano bio field, the development of cells and Taylor-made medicine for a potential treatment of incurable diseases has been a center of attention. The melting point of gelatin is between 25 and 33 °C, and the sol---gel transition occurs in low temperature. This makes the deformation of this useful biomaterial easy. The examples of gelatin fiber applications are suture threads, blood vessel prosthesis, cell-growth-based materials, filter materials, and many others. Because the cell size differs depending on the species and applications, it is essential to fabricate gelatin fibers of different diameters. In this paper, we have developed a fabrication method for gelatin fibers the coacervation method. We fabricated narrow gelatin fibers having a diameter over 10 μm.

Versatile multicharacterization platform involving tailored superhydrophobic SU-8 micropillars for the investigation of breast cancer estrogen receptor isoforms

Here, the authors report the fabrication of lotus-leaf-like tailored SU8 micropillars and their application in the context of a multitechnique characterization protocol for the investigation of the structural properties of the two estrogen receptors (ERα66/ERα46). ER (α) expression is undoubtedly the most important biomarker in breast cancer, as it provides the index for sensitivity to endocrine treatment. Beside the well-characterized ERα66 isoform, a shorter one (ERα46) is also expressed in ERα positive breast cancers and breast cancer cell lines. The superhydrophobic supports were developed by using a two-step approach including an optical lithography process and a plasma reactive ion roughening one. Upon drying on the micropillars, the biological samples resulted in stretched fibers of different diameters which were then characterized by synchrotron x-ray diffraction (XRD), Raman and Fourier-transform infrared spectroscopy. The evidence of both different spectroscopic vibrational responses and XRD signatures in the two estrogen receptors suggests the presence of conformational changes between the two biomarkers. The SU8 micropillar platform therefore represents a valid tool to enhance the discrimination sensitivity of structural features of this class of biomarkers by exploiting a multitechnique in situ characterization approach.

Valve Tissue Engineering with Living Absorbable Threads.

Tissue engineering (TE) depends on the population of scaffolds with appropriate cells, arranged in a specific physiological direction using a variety of techniques. Here, a novel technique of creating "living threads" is described based on thin (poly(ε-caprolactone) fibers of different diameters (23-243 μm). The fibers readily attract human mesenchymal stem cells (MSCs), which are firmly adhered. These versatile fibers can be used to produce dimensional shapes identical in shape to the cup-like structure of a normal human valve, while preserving the specific orientation of both the cells and the fibers. The MSCs on leaflets and the cells cultured in flask shown similar epitopes expression when analyzed by fluorescence activated cell sorting. Together, these characteristics have important functional implications as living absorbable fibers can be a valuable resource in TE of living tissues, including heart valves.

Characterization and preparation of bioinspired resorbable conduits for vascular reconstruction

Soft tissues such as blood vessels possess mechanical behavior characterized by a ‘J-shaped’ stress-strain curve with a low-stiffness and a highly elastic zone. These biomechanical characteristics result in rapid endothelialization, smooth muscle cell regeneration, and aneurysm inhibition. The objective of this study was to fabricate biodegradable vascular grafts mimicking the mechanical properties of native arteries. Vascular grafts (inner diameter = 5.0 mm, length = 2.0 cm) were fabricated by dip coating poly(L-lactide-co-e-caprolactone) (PLCL) copolymers on polydioxanone (PDO) fibers. We used PDO fibers of different diameters to yield vascular grafts with a range of mechanical properties. Biomechanical properties, microstructure, and biocompatibility of the grafts were assessed using circumferential tensile testing, burst pressure measurement, scanning electron microscopy, and subcutaneous implantation, respectively. Vascular grafts possessed circumferential tensile strength and strain in the range of 4.07 to 5.98 MPa and 2.83 to 3.47 MPa, respectively, and were circumferentially stronger than expanded polytetrafluoroethylene (ePTFE) grafts. Burst pressure was physiologically relevant in the range of 1323.0 to 1736 kPa and water entry pressure was between 102.66 to 257.33 kPa. Mechanical properties of the grafts were also assessed in vivo after subcutaneous implantation in Sprague-Dawley rats for up to 8 weeks. Examination of the retrieved grafts indicated that the ‘J-shaped’ strain/stress curve was maintained for up to 3 week in PDO/PLCL vascular grafts. In contrast, ePTFE grafts did not maintain ‘J-shaped’ stress-strain behavior after in vivo implantation. Histological analysis demonstrated cellularization within PDO/PLCL grafts, whereas, PTFE grafts showed cellularization and neotissues mainly at the outer side. Our results suggest a new methodology for the fabrication of biodegradable vascular grafts with mechanical behaviour comparable to the native arteries that might avoid failure due to mechanical mismatch between the graft and native arteries.

Abrasive wear of epoxy composites filled by abrasive particles and reinforced by polyamide fibres

Abrasive wear caused by sandy soil of steel coated by epoxy resin was investigated. Experiments were carried out using an abrasive wear tester developed to simulate the wear of the tillage tools under controlled testing conditions. Epoxy coatings were filled by abrasive particles such as aluminium oxide, silicon carbide and silicon oxide of different particle size. Also, epoxy coatings were reinforced by polyamide fibres of different diameters. The test results showed that, relatively lower wear values were displayed by epoxy coatings filled by silicon oxide particles of 5 wt% content. The wear values performed by silicon oxide of (10–20) μm particle size were lower than that displayed by uncoated steel surface. Solid lubricant such as graphite and molybdenum disulphide as filling material caused significant increase in wear due to the weak adhesion between epoxy/solid lubricant layers. Wear of epoxy reinforced by polyamide fibres showed the minimum wear values. Orientation of fibres much affected wear. Parallel fibres represented higher wear than perpendicular ones. The minimum wear was observed for cross plied coatings where shorter wear tracks and higher tensile strength in both perpendicular and parallel directions were existed. The minimum wear values which were lower than that displayed by uncoated steel test specimens were displayed by 0.1 and 0.3 mm polyamide fibre diameters. This observation confirmed the application of the polyamide fibres as reinforcement in epoxy coatings.