Small-diameter Fibers Research Articles

Electrospun PVP/TiO2 Nanofibers for Filtration and Possible Protection from Various Viruses like COVID-19

In this study, TiO2 nanofibers were prepared with Polyvinylpyrrolidone (PVP) polymer using sol-gel method via electrospinning technique. Owing to the advantages of small fiber diameter, tunable porosity, low cost, large surface to volume ratio, structure control, light-weight, and less energy consumption, electrospun nanofibers are evolving as an adaptable material with a number of applications, in this case for filtration and environmental/virus protection. Different samples of TiO2/PVP nanofibers have been prepared by changing the parameters to achieve the best result. As the polymer concentration was increased from 6 to 8 wt.% of PVP, diameter of the resultant fibers was seen to be increased, implying decrease in the pore-size of the fibers up to 1.4 nm. Surface morphology has been checked via Scanning Electron Microscope (SEM) images. Crystalline nature has been analyzed by X-ray Crystallography. Using the Bruanauer-Emmett-Teller (BET) test, surface area and porosity has been checked for the suitable application. The synthesized TiO2/PVP nanofibers have tremendous practical potentials in filtration and environmental remediation applications.

Stable Lignin-Rich Nanofibers for Binder-Free Carbon Electrodes in Supercapacitors

In this work, 1,2,4,5-benzenetetracarboxylic acid (BT) is used as a cross-linker to improve the oxidative thermostabilization of lignin-rich nanofibers so that the activated carbon nanofiber (ACNF) sheets can be prepared from lignins. As sources, we used organosolv lignins from sugarcane bagasse (LB), para rubber wood chip (LR), and palm kernel shell (LP). The addition of BT imparts hydrogen bond interactions between BT and lignin and increases the oxidation degree of lignin during the stabilization, enabling retention of nanofiber morphology after heat treatments. The preparation of activated carbon in the form of nanofibers substantially enhances the specific surface area of the materials when compared with the activated carbon powders from pure lignins. The properties of the resulting ACNFs are influenced by the structure and composition of lignins. With the synergistic effects of a small fiber diameter (688 ± 80 nm), a high content of heteroatom (O atomic content ∼5.1%), a high graphitic carbon structure (ID/IG ratio ∼0.98), a high conductivity (NI>0.1nA/A ∼3479 ± 404 pixel μm–2 at 0.5 V), and a high specific surface area (∼2195 m2 g–1), the ACNFs from LB show the highest specific capacitance of 182 F g–1 (at a current density of 0.1 A g–1 in 1.0 M H2SO4 electrolyte) with good cycling stability (95.7% capacitance retention after 6000 cycles). A maximum energy density of 31 W h kg–1 at a power density of 240 W kg–1 can be achieved from the LB/PEO/BT ACNFs. Their performance is almost comparable to that of polyacrylonitrile ACNFs. These findings demonstrate a simple and effective approach to produce lignin-based ACNFs from diverse biomass feedstock for sustainable development of renewable materials for supercapacitor electrodes.

Cutaneous silent period in ulnar neuropathy at the elbow.

The cutaneous silent period (CSP) reflects the function of A-delta sensory fibers. There are few studies on CSP in nerve entrapment syndromes. This study aims to evaluate the neurophysiological abnormalities of small-diameter sensory fibers in ulnar neuropathy at the elbow (UNE) by means of CSP. We consecutively evaluated UNE patients at one electrodiagnostic laboratory. The CSP was obtained upon stimulating the fifth (D5) and third digits, recording from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles. We enrolled 37 UNE patients (mean age 55.4 ± 11.2y) and 30 controls (mean age 51.2 ± 11.1y). The combinations of the D5-APB and D5-FDI mean onset latencies of CSP were significantly more prolonged in patients (83.7 ± 6.8 and 84.5 ± 8ms, respectively) than in controls (78.2 ± 8.1 and 79.4 ± 7.6ms, respectively). The D5-FDI duration of CSP was shorter in patients (52.2 ± 8.3ms) than in controls (55.8 ± 7ms). The mean of the onset latencies of D5-FDI and D5-APB was related to the clinical severity (P=.013 and .0025, respectively). D5-APB and D5-FDI onset latencies were more prolonged and the duration was shorter in the UNE group with absent ulnar sensory nerve action potentials (SNAPs) and axonal motor damage than in patients with preserved SNAPs and with demyelinating damage. CSP was able to demonstrate abnormalities of small-diameter myelinated sensory fibers. This damage was directly related to UNE severity and to axonal damage of motor fibers. Absence of a sensory large-diameter fiber response did not exclude preserved residual small fiber conduction.

Research progress, models and simulation of electrospinning technology: a review.

In recent years, nanomaterials have aroused extensive research interest in the world's material science community. Electrospinning has the advantages of wide range of available raw materials, simple process, small fiber diameter and high porosity. Electrospinning as a nanomaterial preparation technology with obvious advantages has been studied, such as its influencing parameters, physical models and computer simulation. In this review, the influencing parameters, simulation and models of electrospinning technology are summarized. In addition, the progresses in applications of the technology in biomedicine, energy and catalysis are reported. This technology has many applications in many fields, such as electrospun polymers in various aspects of biomedical engineering. The latest achievements in recent years are summarized, and the existing problems and development trends are analyzed and discussed.

A novel sensor design for displacement measurement using plastic optical fiber-based on face-coupling method

The development of displacement sensors is essential in the physical sensor field as the other physical sensors can be derived from the displacement sensor. Here we present a novel sensor structure that is used for displacement measurement. The proposed method relies on the intensity variation between the first and second fibers. The structure contains plastic optical fiber (POF) with large and small diameter fiber. A hole is constructed inside the core of large diameter fiber, and small diameter fiber is placed inside the hole for the displacement measurement. Besides this, a tapered fiber is used to enhance the coupling fabricated with the heat and drawing process. The experimental results show that the sensor's range relies on the hole's length while sensitivity decreased as the length of the hole increased. However, the sensitivity is enhanced using taper fiber. A high resolution and sensitivity are achieved with this POF sensor structure. The displacement sensor has a simple structure, easy to fabricate, and is low-cost. The proposed structure could be used not only for displacement but also for vibration, angle, and pressure sensors.

The deposition of nanofibers onto a traditional filtration medium and their effects on filtration efficiency

Traditional filtration media composed of fibers with sizes on the micrometer scale have difficulty filtering particles a little smaller than 300 nm. Even though nanofibrous materials are able to capture these particles and can have excellent filtration efficiency, their widespread use continues to be inhibited by several obstacles, particularly an excessive pressure drop and the inability to form self-supporting filtration membranes. We have prepared two types of composite materials, namely an ultra-thin nanofibrous layer made of polyurethane or nylon with various fiber diameters and pore areas. Scanning electron microscopy was used for their characterization. The nanofibrous layer was deposited directly onto a traditional melt-blown polypropylene filtration fabric with a very low area weight of 30 g/m2, which facilitates handling and bypasses the need for the layer to be self-supporting. Moreover, a fine polyethylene mesh was added as a separate layer to prevent humidity from passing through the filtration material as well as to cover fabrics. The filtration efficiency and the pressure drop of the prepared materials were determined. The results showed that the incorporation of a nylon nanofibrous layer with smaller fiber diameters and pore areas leads to a significant increase in the filtration efficiency (92%) against the most penetrating particles, the critical size of which decreased to 50 nm, while the pressure drop was comparable to the pressure drop of a commercially available FFP2 respirator. The prepared filtration material could be used to manufacture respirators.

Live weight and Coat Length of Tuvan Coarse-Haired Goats

The research purpose was to determine the morphometric parameters of the coat in animals of productive age. The objects of the study were Tuvan coarse-haired goats at the age of 3 years (n = 20) from the agricultural enterprise “Uurgai” located in the southeastern part of the Republic of Tyva (Russia) bordering Mongolia in the south. Wool samples were taken from the animals from the side behind the shoulder blade for examination using an optical fiber diameter analyzer OFDA 2000. It was found that the length of the down averaged 6.35 ± 0.45 cm (Cv = 31.6). The down in the studied goats is shorter than the covering hair and in 35% of the animals studied it exceeds the length of 7 cm. As a result of wool studies using the optical fiber diameter analyzer OFDA 2000, it was found that the proportion of down hair (less than 30 μm) averages 80.21 ± 1.57% (Cv = 8.8), with a fairly significant difference between the extreme values from 67.52 to 90.84%. The amount of transitional hairs has critical differences from 2.28 to 19.42% at Cv = 64.6, while in animals with a low content of transitional hair in the staple (2.28–4.14%), the peak of the diagram has a value within 15–17 μm with a correlation coefficient of 0.69. The data obtained allows for the following conclusion: in order to obtain high-quality down with the smallest fiber diameter when breeding native Tuvan coarse-wooled goat, special attention should be paid to the presence of a transitional hair type (30.1–52.5 μm) in addition to the length of the down and its diameter.

Tension Sensor Based on Fluorescence Resonance Energy Transfer Reveals Fiber Diameter-Dependent Mechanical Factors During Myelination.

Oligodendrocytes (OLs) form a myelin sheath around neuronal axons to increase conduction velocity of action potential. Although both large and small diameter axons are intermingled in the central nervous system (CNS), the number of myelin wrapping is related to the axon diameter, such that the ratio of the diameter of the axon to that of the entire myelinated-axon unit is optimal for each axon, which is required for exerting higher brain functions. This indicates there are unknown axon diameter-dependent factors that control myelination. We tried to investigate physical factors to clarify the mechanisms underlying axon diameter-dependent myelination. To visualize OL-generating forces during myelination, a tension sensor based on fluorescence resonance energy transfer (FRET) was used. Polystyrene nanofibers with varying diameters similar to neuronal axons were prepared to investigate biophysical factors regulating the OL-axon interactions. We found that higher tension was generated at OL processes contacting larger diameter fibers compared with smaller diameter fibers. Additionally, OLs formed longer focal adhesions (FAs) on larger diameter axons and shorter FAs on smaller diameter axons. These results suggest that OLs respond to the fiber diameter and activate mechanotransduction initiated at FAs, which controls their cytoskeletal organization and myelin formation. This study leads to the novel and interesting idea that physical factors are involved in myelin formation in response to axon diameter.

Peripheral Nerve Stimulation: A Review of Techniques and Clinical Efficacy.

Chronic pain is a common source of morbidity in many patient populations worldwide. There are growing concerns about the potential side effects of currently prescribed medications and a continued need for effective treatment. Related to these concerns, peripheral nerve stimulation has been regaining popularity as a potential treatment modality. Peripheral nerve stimulation components include helically coiled electrical leads, which direct an applied current to afferent neurons providing sensory innervation to the painful area. In theory, the applied current to the peripheral nerve will alter the large-diameter myelinated afferent nerve fibers, which interfere with the central processing of pain signals through small-diameter afferent fibers at the level of the spinal cord. Multiple studies have shown success in the use of peripheral nerve stimulation for acute post-surgical pain for orthopedic surgery, including post total knee arthroplasty and anterior cruciate ligament surgery, and chronic knee pain. Many studies have investigated the utility of peripheral nerve stimulation for the management of chronic shoulder pain. Peripheral nerve stimulation also serves as one of the potential non-pharmacologic therapies to treat back pain along with physical therapy, application of transcutaneous electrical neurostimulation unit, radiofrequency ablation, epidural steroid injections, permanently implanted neurostimulators, and surgery. Studies regarding back pain treatment have shown that peripheral nerve stimulation led to significant improvement in all pain and quality-of-life measures and a reduction in the use of opioids. Further studies are needed as the long-term risks and benefits of peripheral nerve stimulation have not been well studied as most information available on the effectiveness of peripheral nerve stimulation is based on shorter-term improvements in chronic pain.

Fascia Mobility, Proprioception, and Myofascial Pain.

The network of fasciae is an important part of the musculoskeletal system that is often overlooked. Fascia mobility, especially along shear planes separating muscles, is critical for musculoskeletal function and may play an important, but little studied, role in proprioception. Fasciae, especially the deep epimysium and aponeuroses, have recently been recognized as highly innervated with small diameter fibers that can transmit nociceptive signals, especially in the presence of inflammation. Patients with connective tissue hyper- and hypo-mobility disorders suffer in large number from musculoskeletal pain, and many have abnormal proprioception. The relationships among fascia mobility, proprioception, and myofascial pain are largely unstudied, but a better understanding of these areas could result in improved care for many patients with musculoskeletal pain.

Analyzing the effect of misalignment on single-filament carbon fiber tensile testing via stereoscopic computer vision imaging

An understanding of the constitutive properties of carbon fibers (CFs) is critical to the accuracy of high-resolution composite simulations and to the development of CF derived from low-cost alternative precursor materials. Single-fiber tensile testing is a capable tool to measure CF properties and is well suited to research efforts where only a small number of fibers may be available. However, single-fiber tensile tests are challenging to conduct due to the difficulty in handling small diameter fibers (5–15 μm), the brittleness of single fibers, and the required nanoscale/microscale resolution of testing equipment. The accuracy of the measured properties depends on several factors, but a critical factor is fiber misalignment, especially at short gauge lengths. Current standards do not address the effect of tensile specimen misalignment on measured properties. This work presents a robust method of fiber alignment using stereoscopic computer vision that enables users to align fibers vertically for tensile testing to improve the accuracy of resulting mechanical properties. Additionally, an analytical relationship between fiber misalignment angle and measured properties is developed and validated against the experimental results. As a result, new best practices for single-fiber tensile testing of CF are recommended.

A Finitary Structure Theorem for Vertex-Transitive Graphs of Polynomial Growth

We prove a quantitative, finitary version of Trofimov’s result that a connected, locally finite vertex-transitive graph Γ of polynomial growth admits a quotient with finite fibres on which the action of Aut(Γ) is virtually nilpotent with finite vertex stabilisers. We also present some applications. We show that a finite, connected vertex-transitive graph Γ of large diameter admits a quotient with fibres of small diameter on which the action of Aut(Γ) is virtually abelian with vertex stabilisers of bounded size. We also show that Γ has moderate growth in the sense of Diaconis and Saloff-Coste, which is known to imply that the mixing and relaxation times of the lazy random walk on Γ are quadratic in the diameter. These results extend results of Breuillard and the second author for finite Cayley graphs of large diameter. Finally, given a connected, locally finite vertex-transitive graph Γ exhibiting polynomial growth at a single, sufficiently large scale, we describe its growth at subsequent scales, extending a result of Tao and an earlier result of our own for Cayley graphs. In forthcoming work we will give further applications.

The fabrication of a novel film based on polycaprolactone incorporated with chitosan and rutin: potential as an antibacterial carrier for rainbow trout packaging.

Rutin and chitosan could be utilized in the food industry owing to their antioxidant and antibacterial properties. This study was carried out to fabricate novel films using polycaprolactone (PCL-sole), PCL and chitosan (PCL-CS), PCL and rutin (PCL-R), and PCL, chitosan, and rutin (PCL-CS-R) through electros pinning method. Physical properties, in vitro antibacterial and antioxidant properties of the films, and their antibacterial activity on rainbow trout were further investigated. The PCL-CS, PCL-R, and PCL-CS-R had smaller fiber diameter and film thickness and lower viscosity while they showed higher surface tension, water contact angle, and conductivity and better antibacterial and antioxidant properties compared with PCL-sole film (P < 0.05). The PCL-CS-R film respectively decreased 17.45%, 19.27%, and 18.39% more populations of L. monocytogenes, S. aureus, and E. coli compared to PCL-sole film in the fish samples. Therefore, the PCL-CS-R film can be potentially used in active packaging because of its antioxidant and antibacterial activities.

Small-diameter optical fibre sensor embedment for ambient temperature cure monitoring and residual strain evaluation of CFRP composite laminates produced by vacuum-assisted resin infusion

Out of autoclave (OoA) processing techniques, such as liquid composite moulding techniques (LCM) and, particularly, the vacuum-assisted resin infusion (VARI) technique, are being used, with increasing success, in replacement of prepreg/autoclave technologies to produce structural aircraft/aerospace polymer composite parts, due to its better cost effectiveness and competitiveness. This work aims to embed Fibre Bragg grating (FBG) sensors to monitor the VARI manufacturing of carbon fibre reinforced polymer (CFRP) composites and evaluate the associated phenomena: ambient curing and post curing reactions and resulting residual strains. The curing kinetics of the epoxy resin system alone was initially studied through isothermal differential scanning calorimetry (DSC) tests and applying the isoconversional Friedman method, and further studied by strain monitoring during ambient curing and post curing resorting to FBG sensors. The FBG sensors in the CFRP laminates were able to detect a subtle increase of strain as infusion of the CFRP started and to measure decreasing strain as resin filled in the dry fabric layers. Subtle strain decrease revealed forming crosslink bonds. Compressive strains measured by the FBG sensors during post curing show that further crosslink takes place. A comparison of resultant residual strains was made between specimens with embedded FBG sensors on small-diameter optical fibres (SDOF) and on large-diameter optical fibres (LDOF).

Effects of Temperature on Melt Electrospinning: Experiment and Simulation Study

In this study, the jet formation progress, jet motion, resultant fiber diameter, fiber mat morphology, inner structures and mechanical properties of the fibers prepared at different heating temperatures via melt electrospinning system were studied, in a comprehensive and systematic manner. The temperature distribution of the melt electrospinning configuration was simulated, in order to provide a good deal of insight into the experimental results. High-speed photography was adopted to capture the images of jet formation process and jet motion during melt electrospinning. The experimental results showed that higher heating temperature at the spinneret results in shorter jet formation time, smaller fiber diameter, more disordered fiber mat, lower degree of crystallinity and strength. The simulation works was carried out, aimed at facilitating to deeply understand the experimental results.

Non-monotonic kilohertz frequency neural block thresholds arise from amplitude- and frequency-dependent charge imbalance

Reversible block of nerve conduction using kilohertz frequency electrical signals has substantial potential for treatment of disease. However, the ability to block nerve fibers selectively is limited by poor understanding of the relationship between waveform parameters and the nerve fibers that are blocked. Previous in vivo studies reported non-monotonic relationships between block signal frequency and block threshold, suggesting the potential for fiber-selective block. However, the mechanisms of non-monotonic block thresholds were unclear, and these findings were not replicated in a subsequent in vivo study. We used high-fidelity computational models and in vivo experiments in anesthetized rats to show that non-monotonic threshold-frequency relationships do occur, that they result from amplitude- and frequency-dependent charge imbalances that cause a shift between kilohertz frequency and direct current block regimes, and that these relationships can differ across fiber diameters such that smaller fibers can be blocked at lower thresholds than larger fibers. These results reconcile previous contradictory studies, clarify the mechanisms of interaction between kilohertz frequency and direct current block, and demonstrate the potential for selective block of small fiber diameters.

Evaluation of a one-dimensional position-sensitive quartz optical fiber sensor based on the time-of-flight method for high radiation dose rate applications

For the measurement of radiation distribution inside the Fukushima Daiichi Nuclear Power Station (FDNPS) buildings, the evaluation of a small-diameter quartz optical fiber as a one-dimensional position-sensitive sensor was conducted. The sensor determines the incident position of radiation into the fiber using the time-of-flight information from the Cerenkov photons generated in the optical fiber. Compared with a conventional sensor using plastic scintillating fiber, the quartz optical fiber has a much higher position resolution, which may be the result of the improvement of timing characteristics due to the prompt emission mechanism of the Cerenkov radiation. Additionally, the response of the quartz fiber sensor under high radiation field was evaluated. A count rate linearity up to a dose rate of at least 20 mSv/h was confirmed using a 10m-long quartz fiber with a diameter of 0.4 mm. Furthermore, the radiation tolerance of the sensor up to an accumulated dose of 1 kGy was evaluated.

Evaluation of wound healing efficiency of vancomycin-loaded electrospun chitosan/poly ethylene oxide nanofibers in full thickness wound model of rat

Electrospun hybrid nanofibers have been extensively regarded as drug carriers. This study tries to introduce a nano fibrous wound dressing as a new strategy for a topical drug-delivery system. The vancomycin (VCM)-loaded hybrid chitosan/poly ethylene oxide (CH/PEO) nanofibers were fabricated by the blend-electrospinning process. Morphological, mechanical, chemical, and biological properties of nanofibers were examined by SEM, FTIR, release profile study, tensile assay, Alamar Blue cytotoxicity evaluation, and antibacterial activity assay. In vivo wound healing activity of hybrid CH/PEO/VCM nanofibers was evaluated in full-thickness skin wounds of rats. The hybrid CH/PEO/VCM nanofibers were successfully fabricated in a nanometer. The CH/PEO/VCM 2.5% had higher Young's Modulus, better tensile strength, smaller fiber diameter with sustained-release profiles compared to CH/PEO/VCM 5%. All nanofibers did not show any significant cytotoxicity (P < 0.05) on the normal fibroblast cells. Also, VCM-load hybrid CH/PEO nanofibers successfully inhibited bacterial growth. The wound area in the rats treated with CH/PEO/VCM 2.5% was less than CH/PEO/VCM 5% treated group. According to histological evaluation, the CH/PEO/VCM 2.5% group showed the fastest wound healing than other treatment groups. Results of this study proposed that CH/PEO/VCM nanofibers could promote the wound healing process by reducing the side effects of VCM as a topical antimicrobial agent.

Preparation of pitch/polyacrylonitrile carbon nanofiber non-woven fabrics as the electrode for supercapacitors

Pitch/polyacrylonitrile carbon nanofiber non-woven fabrics (P/PAN CNFs) for use as supercapacitor electrode materials were prepared by electrospinning a mixed solution of pitch and PAN, followed by stabilization and carbonization. Results indicate that P/PAN CNFs have a smaller fiber diameter, higher conductivity, larger specific surface area and moderate pore size compared with PAN CNFs, which increases the capacitance and rate capability of the supercapacitors. When the mass ratio of pitch to PAN was 1/1.5, the P/PAN CNF (P/PAN-1/1.5) showed a high capacitance of 219 F g−1 at a current density of 0.1 A g−1, a value 1.38 times that of PAN CNF. When the current density was increased to 50 A g−1, the capacitance retention of the P/PAN-1/1.5 was 69.4%, 42.8% larger than that of PAN CNF. A symmetrical supercapacitor based on P/PAN-1/1.5 had an energy density of 4.8 Wh kg−1 at a power density of 14.8 kW kg−1 and a capacitance retention rate of 94.1% after 20 000 cycles.

Fiber Bridging during Melt Electrowriting of Poly(ε‐Caprolactone) and the Influence of Fiber Diameter and Wall Height

AbstractMelt electrowriting (MEW) is a direct‐writing technology for small diameter fibers; however, due to electrostatic attraction, the technique is restricted in how close these microfibers can be positioned on the collector. Here, the minimum interfiber distance between parallel poly(ε‐caprolactone) MEW microfibers is determined for different fiber diameters and number of layers on noncoated and star‐shaped poly(ethylene oxide‐stat‐propylene oxide) (sP(EO‐stat‐PO))‐coated glass coverslips. The effect of the fiber diameter, the number of fiber layers, and shape of turning loops affect precision and the minimum interfiber distance. Single fibers with diameter of 5, 10, and 15 µm have a minimum interfiber distance without fiber bridging of 33 ± 2.7, 54 ± 2.2, and 62 ± 2.7 µm, respectively. Increasing the number of layers to ten increases this minimum interfiber distance approximately twofold to 60 ± 3.5, 97 ± 4.5, and 102 ± 2.7 µm for the increasing fiber diameters. The sP(EO‐stat‐PO) slightly increases the minimum interfiber distance for the 15 µm diameter group only, with spacing for the 5 and 10 µm fibers unaffected by the coating. Identifying and determining the fabrication limits for MEW is highly instructional for users working and designing scaffolds with this technology.