Large-diameter Fibers Research Articles

Microstructurally informed subject-specific parcellation of the corpus callosum using axonal water fraction.

The corpus callosum (CC) is the most important interhemispheric white matter (WM) structure composed of several anatomically and functionally distinct WM tracts. Resolving these tracts is a challenge since the callosum appears relatively homogenous in conventional structural imaging. Commonly used callosal parcellation methods such as Hofer and Frahm scheme rely on rigid geometric guidelines to separate the substructures that are limited to consider individual variation. Here we present a novel subject-specific and microstructurally-informed method for callosal parcellation based on axonal water fraction (ƒ) known as a diffusion metric reflective of axon caliber and density. We studied 30 healthy subjects from the Human Connectome Project dataset with multi-shell diffusion MRI. The biophysical parameter ƒ was derived from compartment-specific WM modeling. Inflection points were identified where there were concavity changes in ƒ across the CC to delineate callosal subregions. We observed relatively higher ƒ in anterior and posterior areas known to consist of a greater number of small diameter fibers and lower ƒ in posterior body areas of the CC known to consist of a greater number of large diameter fibers. Based on the degree of change in ƒ along the callosum, seven callosal subregions were consistently delineated for each individual. Therefore, this method provides microstructurally informed callosal parcellation in a subject-specific way, allowing for more accurate analysis in the corpus callosum.

Movement behavior and morphological change of droplets on vertically crossed fibers

Droplet capture and coalescence are critical processes for enhancing emulsion separation efficiency in oily wastewater treatment. In this paper, four kinds of motion behaviors and secondary droplet formation behaviors of oil droplets on vertically crossed fibers in a water environment were investigated using high-speed camera technology. The research shows that during the droplet capture process, droplets on large-diameter horizontal fiber exhibit greater lateral spreading, and smaller vertical elongation. Increasing the diameter of horizontal fiber significantly shortens droplet capture time. The capture time on lipophilic fiber intersection of 190–420 μm is 14 ms less than that of 190–190 μm. During the droplet coalescence process, the liquid bridge on large-diameter horizontal fiber is wider, and the droplet contraction ratio is smaller. The droplet contraction ratio on fiber intersection of 190–420 μm is 0.3 smaller than that of 190–190 μm. Increasing the diameter of horizontal fiber can promote rapid fusion between droplets, but lipophobic fibers hinder the degree of fusion and deformation. Furthermore, the diameter and wettability of horizontal fibers have significant effects on the volume of secondary droplets. The volume of secondary droplets increases with the diameter of lipophilic horizontal fiber in the capture process. The volume of secondary droplets on lipophilic horizontal fiber is approximately three times larger than that on lipophobic horizontal fiber in the coalescence process. These findings contribute to understanding the details of coalescence separation and optimizing the design of fiber fillers.

Single-fibre tensile testing of plant fibres: Set-up compliance as a key parameter for reliable assessment of their mechanical behaviour

The use of plant fibres as reinforcements in engineering applications requires reliable determination of their mechanical properties. This work focuses on single-fibre longitudinal tensile testing and the significance of the tensile system compliance for obtaining reliable results. Four types of fibre are tested, namely basalt, aramid, elementary flax fibres and flax fibre bundles. An automated laser scanning method is used to determine their cross-sectional area (CSA) based on circular and elliptical morphological models. The compliance of the tensile system is evaluated by standard and photomechanical analyses, and its influence on the assessment of mechanical properties of the fibres is discussed. Our results show that the evaluation of the compliance is highly dependent on fibre type, but also on the choice of CSA morphological model. The resulting correction on maximum tensile moduli ranges from 6.5 % to 37.6 % for small-diameter fibres, and can reach 55.1 % for large-diameter fibres as flax fibre bundles. Moreover, we evidence that the tensile system compliance is not necessarily constant and evolves with the force range covered during the tensile test. This can have a significant impact on the shape of the stress-strain curves, and hence on the analysis of the overall mechanical behaviour of the fibres.

Development of Cerium Oxide-Laden GelMA/PCL Scaffolds for Periodontal Tissue Engineering.

This study investigated gelatin methacryloyl (GelMA) and polycaprolactone (PCL) blend scaffolds incorporating cerium oxide (CeO) nanoparticles at concentrations of 0%, 5%, and 10% w/w via electrospinning for periodontal tissue engineering. The impact of photocrosslinking on these scaffolds was evaluated by comparing crosslinked (C) and non-crosslinked (NC) versions. Methods included Fourier transform infrared spectroscopy (FTIR) for chemical analysis, scanning electron microscopy (SEM) for fiber morphology/diameters, and assessments of swelling capacity, degradation profile, and biomechanical properties. Biological evaluations with alveolar bone-derived mesenchymal stem cells (aBMSCs) and human gingival fibroblasts (HGFs) encompassed tests for cell viability, mineralized nodule deposition (MND), and collagen production (CP). Statistical analysis was performed using Kruskal-Wallis or ANOVA/post-hoc tests (α = 5%). Results indicate that C scaffolds had larger fiber diameters (~250 nm) compared with NC scaffolds (~150 nm). NC scaffolds exhibited higher swelling capacities than C scaffolds, while both types demonstrated significant mass loss (~50%) after 60 days (p < 0.05). C scaffolds containing CeO showed increased Young's modulus and tensile strength than NC scaffolds. Cells cultured on C scaffolds with 10% CeO exhibited significantly higher metabolic activity (>400%, p < 0.05) after 7 days among all groups. Furthermore, CeO-containing scaffolds promoted enhanced MND by aBMSCs (>120%, p < 0.05) and increased CP in 5% CeO scaffolds for both variants (>180%, p < 0.05). These findings underscore the promising biomechanical properties, biodegradability, cytocompatibility, and enhanced tissue regenerative potential of CeO-loaded GelMA/PCL scaffolds for periodontal applications.

Femtosecond laser direct writing large-area fiber Bragg grating based on diaphragm shaping

We propose and demonstrate a new method of direct writing large-area fiber Bragg grating by femtosecond laser through the coating. By adding an adjustable diaphragm before the focusing objective, we can precisely control the length of the refractive index modulation line along the femtosecond laser incident direction up to 29.1 µm. In combination with femtosecond laser scanning fabrication technology, a uniform refractive index modulation plane can be inscribed in the fiber in a single scanning. Based on the plane-by-plane inscription method, we have fabricated a high-quality high-reflectivity fiber Bragg grating and a chirped fiber Bragg grating on 20/400 double-clad fiber core. The reflectivity of both gratings is greater than 99%, and the insertion loss is as low as 0.165 dB and 0.162 dB, respectively. The thermal slope of chirped fiber Bragg grating without any refrigeration is 0.088 °C/W and there is no obvious temperature increase when using the water cooling. Therefore, the fabrication method of large-area fiber Bragg grating based on diaphragm shaping can efficiently fabricate high-quality fiber Bragg grating in the large core diameter fiber, which has an important application prospect in high-power all-fiber oscillators, especially all-fiber oscillators in special wavebands.

Impact of fiber diameter on mechanical and water absorption properties of short bamboo fiber-reinforced polyester composites

Abstract This study aims to investigate the effect of fiber diameter on the mechanical and water absorption characteristics of short bamboo fiber-reinforced polyester composites. Three different fiber sizes (180–250 µm, 250–500 µm, and 700–1000 µm) were used to prepare composites with varying fiber loadings of 10 wt.%, 20 wt.%, and 30 wt.%. The fabricated composites were cut to standard dimensions, and tension tests, impact tests, and water absorption tests were performed. Reproducible results were obtained, revealing that using fibers of smaller diameter (180–250 µm) increased the tensile strength of the composite by 20 % compared to composites with larger diameter fibers (700–1000 µm), while the tensile modulus showed a 22 % enhancement with decreasing fiber diameter. Composites with larger diameter fibers exhibited more defects (voids and matrix detachment), as revealed by SEM analysis of fractured surfaces. The impact strength of composites with a diameter size of 700–1000 µm increased by 33 % compared to composites reinforced with the smallest fiber diameter. Water absorption of the composites was also studied by long-term immersion in water, showing that water intake was high initially, reaching a saturation point after a certain time interval. The absorbed water values indicated that composites with the smallest diameter (180–250 µm) showed maximum water intake due to the creation of more water intake sites (increased interfacial area), while composites with the largest diameter fibers (700–1000 µm) exhibited the least water absorption as the interaction region between fibers and matrix was reduced.

Fabrication of electrostatic-induction-assisted solution blowing spinning nanofibers and its mechanism

Commonly used nanofiber fabrication technologies have many shortcomings: the yield of electrospinning is low, solution blowing spinning (SBS) and its improved technologies have problems with large fiber diameter, non-uniform nanofiber diameter and poor receiving aggregation of nanofibers on receiver. A nanofiber fabrication technology called electrostatic-induction-assisted solution blowing spinning (ESBS), which overcomes these disadvantages, was developed in this paper. This technology utilizes the joint action of electrostatic force and airflow stretching force to stretch the jet to fabricate nanofibers. The grounding of the blunt needle realizes the directional migration and dynamic circulation of charges in the ESBS microscopic system. Compared with traditional SBS, the average diameter and diameter standard deviation of ESBS nanofibers can be reduced by 44 % and 80.8 %, respectively, and the fiber cover rate can be increased by 329.7 %. In contrast to the cylindrical-electrode-assisted solution blowing spinning, the mean diameter and diameter standard deviation of ESBS nanofibers can be reduced by 34.6 % and 68.1 %, respectively, and the fiber cover rate can be increased by 305 %. The microcosmic fabrication mechanism of ESBS nanofibers—“the theory of separation and directional transfer of charges” was proposed and verified. ESBS nanofibers with single-needle injection speed up to 200 μl/min (far exceeding the 4–10 μl/min injection speed of conventional electrospinning) were successfully fabricated to prove that this technology has great industrial potential. ESBS nanofibers with small and uniform diameter, high yield, and good receiving aggregation of fibers on receiver have bright application prospects in many fields.

Effect of the solid content of spinning solutions on the structure properties of large-diameter polyvinyl alcohol fiber

Effect of the solid content of spinning solutions on the structure properties of large-diameter polyvinyl alcohol fiber

Fabrication and biocompatibility evaluation of hydroxyapatite-polycaprolactone-gelatin composite nanofibers as a bone scaffold.

One approach to addressing bone defects involves the field of bone tissue engineering, with scaffolds playing an important role. The properties of the scaffold must be similar to those of natural bone, including pore size, porosity, interconnectivity, mechanical attributes, degradation rate, non-toxicity, non-immunogenicity, and biocompatibility. The primary goals of this study are as follows: first, to evaluate hydroxyapatite (HA)/polycaprolactone (PCL)/gelatin nanofiber scaffolds based on functional groups, fibre diameter, porosity, and degradation rate; second, to investigate the interaction between HA/PCL/gelatin scaffolds and osteoblast cells (specifically, the ATCC 7F2 cell line) using in vitro assays, including cell viability and adhesion levels. The fibre samples were fabricated using an electrospinning technique with a 15 kV voltage, a spinneret-collector distance of 10 cm, and a flow rate of 0.3 mL hour-1. The process was applied to five different HA/PCL/gelatin concentration ratios: 50 : 40 : 10; 50 : 30 : 20; 50 : 25 : 25; 50 : 20 : 30; 50 : 35 : 15 (in %wt). Fourier Transform Infrared (FTIR) spectrum analysis and tests revealed no differences in functional groups across the five compositions. The identified functional groups include PO4 3-, OH-, CO3 2- and C[double bond, length as m-dash]O stretching. Notably, an increase in PCL concentrations resulted in larger fiber diameters, ranging from 369-1403 nm with an average value of 929 ± 175 nm. The highest porosity percentage was (77.27 ± 11.57) %, and a sufficient degradation rate of up to 3.5 months facilitated the proliferation process of osteoblast cells. Tensile strength assessments revealed a significant increase in tensile strength with the addition of PCL, reaching a peak of 1.93 MPa. The MTT assay demonstrated a discernible increase in cell proliferation, as evidenced by increased cell viability percentages on days 1, 3, and 5. Concurrently, the fluorescence microscopy examination indicated an increase in cell numbers, which was especially noticeable on days 1 and 5. The SEM analysis confirmed the biocompatibility of the HA/PCL/gelatin nanofiber scaffold, as osteoblast cells attached and dispersed successfully five days after seeding. Based on these findings, the HA/PCL/gelatin nanofiber scaffold emerges as a very promising candidate for treating bone damage.

Amine-functionalized UiO-66 incorporated electrospun cellulose/chitosan porous nanofibrous membranes for removing copper ions

Cellulose (CE)/chitosan (CS)/amine-functionalized zirconium 1, 4-dicarboxybenzene metal–organic framework (UiO-66-NH2) porous nanofiber membranes were prepared by direct electrospinning and surface in-situ growth and then used to remove copper ions (Cu2+) from polluted water. The micro-morphology, porosity, thermal stability, chemical groups, crystallographic structure, and adsorption performance of CE/CS/UiO-66-NH2 nanofibrous membranes were characterized. The hydrophilicity, thermal stability, and adsorption capacity of the membranes were greatly improved by incorporating UiO-66-NH2. The direct electrospinning CE/CS/UiO-66-NH2 nanofibers displayed the irregular, bumpy shapes and large fiber diameters (768.99–1039.74 nm). They also increased the chemical active sites due to the effective and uniform combination of UiO-66-NH2 with nanofibers. This resulted in a superior adsorption performance than the one with in-situ preparation. The CE/CS/UiO-66-NH2-5 showed the highest adsorption capacity of 121.16 mg g−1 and a removal rate of 90.69 %. The optimal Cu2+ adsorption conditions were obtained at an initial Cu2+ concentration of 100 mg L-1 and in weakly acidic media (pH = 5). The Langmuir model was optimal to describe Cu2+ adsorption of the nanofibrous membranes. The adsorption process involved both physical adsorption with chemical adsorption. This provides a novel strategy to combine metal–organic frameworks with the natural biomasses via electrospinning, which shows a promising application for efficient remediation of heavy metal ions in wastewater.

Histological and morphometric analysis of skeletal muscle in some vertebrates

The skeletal system is primarily driven by the skeletal muscles to produce kinematic movements. The study evaluates the histological and morphometric properties of skeletal muscle in Clarias gariepenus (Cl. gariepinus), Bufo bufo (B. bufo), Agama agama (A. agama), Columba livia domestica (C. domestica) and Rattus rattus (R. rattus). The study was carried in order to relate the similarities and differences of skeletal muscles in these species with evolutionary trend. The epaxial muscle of Cl. Gariepinus, the biceps femoris muscle of B. bufo, R. rattus, puboischiotibialis of A. agama, and pectoral muscle from C. domestica were removed and assessed grossly for physical appearance then processed for histological analysis. The diameters of the muscle fibers were measured and one-way analysis of variance was used to compare the differences. The muscles of Cl. gariepinus, B. bufo and A. agama appeared whitish with scanty fusiform nucleus and large intermuscular space. However, the muscles of C. domestica and R. rattus appeared red with distinct round nucleus and small intermuscular space. No significant difference (P&gt;0.05) was observed in the muscle diameter of Cl. gariepinus (8.86±0.13µm) compared to B. bufo (8.25±0.27µm). The muscle diameter of A. agama (10.18±0.25µm) was significantly higher (P&lt;0.05) relative to Cl. gariepinus (8.86±0.13µm), B. bufo (8.25±0.27µm), C. domestica (3.38±0.13µm) and R. rattus (4.66±0.15µm). Conclusively, non-tetrapod vertebrates (Cl. gariepinus, B. bufo, and A. agama) have simple, white-colored skeletal muscle with few flat-shaped nuclei and large fiber diameters while higher vertebrates (C. domestica and R. rattus) have complex, red-colored skeletal muscle with numerous oval-shaped nucleus and small fiber diameter.

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.

Fibroblast Growth Factor Soaked Collagen Membrane Shows No Biomechanical or Histological Advantages in the Treatment of Chronic Rotator Cuff Tears in a Rabbit Model

To investigate the histological and biomechanical effects of a fibroblast growth factor (FGF-2)-soaked collagen membrane used to treat a full-thickness chronic rotator cuff (RC) rupture in a rabbit model. Forty-eight shoulders from 24 rabbits were used. At the beginning of the procedure, 8 rabbits were killed to assess the control group (Group IT) with intact tendons. To establish a chronic RC tear model, a full-thickness subscapularis tear was created on both shoulders of the remaining 16 rabbits and left for 3 months. The transosseous mattress suture technique was used to repair tears in the left shoulder (Group R). The tears in the right shoulder (Group CM) were treated using the same approach, with an FGF-soaked collagen membrane inserted and sutured over the repair site. Three months after the procedure, all rabbits were killed. Biomechanical testing was performed on the tendons to determine failure load, linear stiffness, elongation intervals, and displacement. Histologically, the modified Watkins score was used to evaluate tendon-bone healing. There was no significant difference among the three groups in terms of failure load, displacement, linear stiffness, and elongation (P > .05). The total modified Watkins score was not affected by applying the FGF-soaked collagen membrane to the repair site (P > .05). Fibrocytes, parallel cells, large-diameter fibers, and the total modified Watkins score were significantly lower in both repair groups when compared to the intact tendon group (P < .05). In addition to tendon repair, FGF-2 soaked collagen membrane -application at the repair site provides neither biomechanical nor histological advantages in the treatment of chronic RC tears. FGF-soaked collagen membrane augmentation provides no impact on the chronic RC tear healing tissue. The need to investigate alternative methods that may have a positive effect on healing in chronic RC repairs continues.

Ultralight and Superelastic Curly Micro/Nanofibrous Aerogels by Direct Electrospinning Enable High-Performance Warmth Retention.

Extremely low temperature has posed huge burden on the public safety concerns and global economics, thereby calling for high-performance warmth retention materials to resist harsh environment. However, most present fibrous warmth retention materials are limited by their large fiber diameter and simple stacking structure, leading to heavy weight, weak mechanical property, and limited thermal insulation performance. Herein, an ultralight and mechanically robust polystyrene/polyurethane fibrous aerogel by direct electrospinning for warmth retention is reported. Manipulation of charge density and phase separation of charged jet allows for the direct assembly of fibrous aerogels consisting of interweaved curly wrinkled micro/nanofibers. The resultant curly wrinkled micro/nanofibrous aerogel possesses low density of 6.8mgcm-3 and nearly full recovery from 1500-cycle deformations, exhibiting both ultralight feature and superelastic property. The aerogel also shows low thermal conductivity of 24.5mWm-1 K-1 , making synthetic warmth retention materials superior to down feather possible. This work may shed light on developing versatile 3Dmicro/nanofibrous materials for environmental, biological, and energy applications.

Flame-retardant, ultralight, and superelastic electrospun fiber sponges for effective sound absorption

Traffic noise does great harm to the physical and mental health of humans, which has become the main source of noise pollution, making sound absorption materials highly in demand. Fibrous sound-absorbing materials are widely used in controlling traffic noise pollution; nevertheless, due to the monotonic internal structure and large fiber diameter, they suffer poor mechanical properties and sound absorption performance. Herein, we develop a credible way to create flame-retardant fibrous sound absorption sponges by humidity-assisted electrospinning and an in-situ crosslinking approach. The obtained fibrous sponges possess outstanding superelastic and hydrophobic properties. Most importantly, fluffy fiber networks endow sponges with good low-frequency sound-absorbing properties (noise reduction coefficient or NRC of 0.51) and lightweight features (density of 9 mg cm−3) compared with commercial and reported sound-absorbing materials. This work will shed light on future research in developing excellent sound-absorbing materials.

A Novel Large-Diameter Optical Fiber Glucose Biosensor Based on Glucose Oxidase– Graphene Oxide–Gold Nanoparticles

A novel glucose large-diameter optical fiber LSPR sensor was constructed based on chemical cross-linking and electrostatic methods of glucose oxidase-graphene oxide-gold nanoparticles (GOD-GO-AuNPs). The GOD-catalyzed oxidation of glucose reacts with oxygen to produce gluconic acid and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , leading to a change in its ambient refractive index, which in turn leads to a significant shift in the LSPR peak of GO-AuNPs on the fiber. The structure and morphology of GOD-GO-AuNPs were studied by FTIR, UV-vis spectroscopy, SEM, and TEM, respectively. GO improves the stability of the composite particles, reduces the biotoxicity of the metal particles, and the immobilization of glucose oxidase on the surface of the composite particles improved the enzyme activity. A fiber-optic sensor was prepared based on the optimal conditions, and the sensitivity of the sensor was 11.134 nm/(mg/mL) in the range of 0 to 1.0 mL with a response time of 55 s. It showed good anti-interference, selectivity and can be used for real detection. This method combines the advantages of GO, AuNPs, and large diameter fiber-optical which show promise for simple, stable, and cost-effective applications in the field of glucose detection.

Covariation of the amplitude and latency of motor evoked potentials elicited by transcranial magnetic stimulation in a resting hand muscle

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique used to study human neurophysiology. A single TMS pulse delivered to the primary motor cortex can elicit a motor evoked potential (MEP) in a target muscle. MEP amplitude is a measure of corticospinal excitability and MEP latency is a measure of the time taken for intracortical processing, corticofugal conduction, spinal processing, and neuromuscular transmission. Although MEP amplitude is known to vary across trials with constant stimulus intensity, little is known about MEP latency variation. To investigate MEP amplitude and latency variation at the individual level, we scored single-pulse MEP amplitude and latency in a resting hand muscle from two datasets. MEP latency varied from trial to trial in individual participants with a median range of 3.9 ms. Shorter MEP latencies were associated with larger MEP amplitudes for most individuals (median r = − 0.47), showing that latency and amplitude are jointly determined by the excitability of the corticospinal system when TMS is delivered. TMS delivered during heightened excitability could discharge a greater number of cortico-cortical and corticospinal cells, increasing the amplitude and, by recurrent activation of corticospinal cells, the number of descending indirect waves. An increase in the amplitude and number of indirect waves would progressively recruit larger spinal motor neurons with large-diameter fast-conducting fibers, which would shorten MEP onset latency and increase MEP amplitude. In addition to MEP amplitude variability, understanding MEP latency variability is important given that these parameters are used to help characterize pathophysiology of movement disorders.

Numerical simulation of two-phase flow in gas diffusion layer and gas channel of proton exchange membrane fuel cells

Liquid water within the cathode Gas Diffusion Layer (GDL) and Gas Channel (GC) of Proton Exchange Membrane Fuel Cells (PEMFCs) is strongly coupled to gas transport properties, thereby affecting the electrochemical conversion rates. In this study, the GDL and GC regions are utilized as the simulation domain, which differs from previous studies that only focused on any one of them. A Volume of Fluid (VOF) method is adopted to numerically investigate the two-phase flow (gas and liquid) behavior, e.g., water transport pattern evolution, water coverage ratio as well as local and total water saturation. To obtain GDL geometries, an in-house geometry-based method is developed for GDL reconstruction. Furthermore, to study the effect of GDL carbon fiber diameter, the same procedure is used to reconstruct three GDL structures by varying the carbon fiber diameter but keeping the porosity and geometric dimensions constant. The wall wettability is introduced with static contact angles at carbon fiber surfaces and channel walls. The results show that the GDL fiber microstructure has a significant impact on the two-phase flow patterns in the cathode field. Different stages of two-phase flow pattern evolution in both cathode domains are observed. The liquid water in the GDL experiences water invasion, spreading, and rising, followed by the droplet breakthrough in the GDL/GC interface. In the GC, the water droplets randomly experience accumulation, combination, attachment, and detachment. Due to the difference in surface wettability, the water coverage of the GDL/GC interface is smaller than that of the channel side and top walls. It is also found that the water saturation inside the GDL stabilizes after the water breakthrough, while local water saturation at the interface keeps irregular oscillations. Last but not the least, a water saturation balance requirement between the GDL and GC is observed. In terms of varying fiber diameter, a larger fiber diameter would result in less water saturation in the GDL but more water in the GC, in addition to faster water movement throughout the total domain.

Experimental study on 80 MPa grade light transmitting concrete with high content of optical fibers and eco-friendly raw materials

Arranging optical fibers with high content in the light transmitting concrete (LTC) helps to enhance the light transmission ability of this material. To develop thinner LTC panels with higher light transmittance, simultaneous improvement of mechanical strength and fiber content is a crucial issue. In addition, since LTC is a material that helps to reduce the environmental impacts, the use of eco-friendly raw materials in the LTC production should also be considered. This study aims to (i) develop the 80 MPa grade LTC with high content of optical fibers and eco-friendly raw materials, (ii) limit the phenomenon of strength reduction with increasing fiber content as in previous studies, and (iii) clarify the effect of temperature, light source distance and fiber diameter on light transmittance of LTC. A series of experiments is conducted to optimize the concrete mixture composition and clarify the mechanical strength, light transmission of LTC samples. The results show that the mixture composition with high workability can be used to develop the 80 MPa grade LTC with an optical fiber volume content of up to 7.1 %. The Scanning Electron Microscope observation results show no significant gaps around optical fibers in the highest content case. The diameter, content, and orientation of the optical fibers do not significantly affect the compressive and flexural strength of LTC. In addition, the results of scattering characteristics of light passing through optical fibers show that the LTC with small diameter fiber suits for wide area illumination and the one with the larger diameter fiber suits for illuminating high-intensity light in a narrow region.

Development of multiscale Fe/SiC–C fibrous composites for broadband electromagnetic and acoustic waves absorption

The explosive development of wireless communication devices and modern electronic machines raises concerns about potential human health threats from their extensive emission of electromagnetic waves (EMW) and acoustic noise. However, the insufficient lossy medium, monotonous structure, and large fiber diameters limit the broadband EMW and noise absorption of traditionally used fibrous materials. Here, we developed electro-spun Fe-doped and SiC nanoparticle-loaded carbon fibrous membranes (Fe/SiC–C) and their multiscale composites for effective broadband EMW and acoustic waves absorption performance. The Fe/SiC–C fibrous membranes show an excellent EMW absorption bandwidth (EAB) of 6.98 GHz at a thickness of 2.45 mm. Integrating a macroscale double-layer periodic cuboid design, we fabricated Fe/SiC–C fibrous metastructure composites that exhibit broadband EMW absorption with EAB of 15.2 GHz ranging from 2.8 GHz to 18 GHz at a total thickness of 8.45 mm. Additionally, using a simple roll-up method, we assembled the Fe/SiC–C fibrous membranes into a bulk sound absorber with a superior noise reduction coefficient (NRC) of 0.57 at a thickness of 30 mm. The multiscale development of carbon-based fibrous composites enables their potential application to electromagnetic and acoustic waves absorption.