Microstructured Fiber Research Articles

Uniaxial mechanical stretch properties correlated with three-dimensional microstructure of human dermal skin.

The intact and healthy skin forms a barrier to the outside world and protects the body from mechanical impact. The skin is a complex structure with unique mechano-elastic properties. To better direct the design of biomimetic materials and induce skin regeneration in wounds with optimal outcome, more insight is required in how the mechano-elastic properties emerge from the skin's main constituents, collagen and elastin fibers. Here, we employed two-photon excited autofluorescence and second harmonic generation microscopy to characterize collagen and elastin fibers in 3D in 24 human dermis skin samples. Through uniaxial stretching experiments, we derive uni-directional mechanical properties from resultant stress-strain curves, including the initial Young's modulus, elastic Young's modulus, maximal stress, and maximal and mid-strain values. The stress-strain curves show a large variation, with an average Young's modules in the toe and linear regions of 0.1 MPa and 21 MPa. We performed a comprehensive analysis of the correlation between the key mechanical properties with age and with microstructural parameters, e.g., fiber density, thickness, and orientation. Age was found to correlate negatively with Young's modulus and collagen density. Moreover, real-time monitoring during uniaxial stretching allowed us to observe changes in collagen and elastin alignment. Elastin fibers aligned significantly in both the heel and linear regions, and the collagen bundles engaged and oriented mainly in the linear region. This research advances our understanding of skin biomechanics and yields input for future first principles full modeling of skin tissue.

Applications of Microstructured Optical Fibers in Ultrafast Optics: A Review

With the development of laser technology, microstructured optical fibers (MOFs) have become an important part of ultrafast optics, providing excellent platforms for ultrafast laser pulse generation, amplification, and compression, promoting the development of fiber laser systems to generate high power, high pulse energy, and few-cycle duration pulses. MOFs extend the ultrafast laser spectrum to the vacuum ultraviolet (VUV) and even extreme ultraviolet (EUV) regions based on dispersive wave emission and high harmonic generation, as well as to the mid-infrared region based on soliton self-frequency shift (SSFS), contributing compact and low-cost light sources for precision microscopy and spectroscopy. In this paper, first several common types of MOFs are introduced, then the various applications of MOFs in ultrafast optics are discussed, mainly focusing on the aspects of ultrafast laser pulse scaling in pulse energy and spectral bandwidth, and finally the possible prospects of MOFs are given.

Effect of Zr content on microstructure and performance of polycrystalline SiC fiber

Effect of Zr content on microstructure and performance of polycrystalline SiC fiber

Pengaruh Perlakuan Kimia Alkalinasi dan Asetilasi terhadap Kekuatan Tarik dan Mikrostruktur Serat Abaka

Today, environmental problems, especially soil pollution due to inorganic waste or waste that does not decompose, are a major problem and need to be solved, especially in developing countries with high populations such as Indonesia. One of the causes of soil pollution problems is the use of inorganic fibers such as glass fiber and carbon fiber. The use of materials that are not environmentally friendly in the industry will cause environmental problems due to nature's inability to decompose the glass fiber material in nature. The focus of this research is to reduce environmental pollution by using natural fibers such as abaca fiber as an alternative to inorganic fibers. This is due to its properties, namely: low density, good specific strength, low price, and a high biodegradable ability so that it can reduce glass fiber or carbon fiber waste that does not decompose. To support this, abaca fiber needs to be hydrophobic so that it becomes compatible with other materials when combined together with other materials. One of the ways that can be done is by alkaline chemical treatment and acetylation using KOH and CH3COOH. Chemical treatment was carried out by dipping abaca banana fibers into a solution of alkaline compounds and acetylated compounds KOH and CH3COOH with a concentration of 5 M and 10 M for 4 hours. After chemical treatment, the abaca banana fibers were characterized for mechanical properties using ASTM D 3379 standards to determine the tensile strength of the fibers and using an optical microscope to determine the microstructure of the abaca fibers.

Novel Ultra-High-Performance Concrete (UHPC) Enhanced by Superhydrophobic and Self-Luminescent Features

This study explores the potential of using basalt reinforced UHPC by incorporating simultaneously self-cleaning and self-luminescent features, paving the way for sustainable advancements in civil engineering. New green formulations of UHPC were developed by integrating supplementary cementitious materials and optimizing water to the binder ratio, followed by using basalt fibers to enhance strength and ductility. The fabricated samples with high particle-packing density exhibit sufficient workability and compressive strength up to 136 MPa, and, when incorporating basalt fibers, a notable reduction in brittleness. The inner microstructure of basalt fibers was observed to be smooth, homogeneously distributed, and well adhered to the UHPC matrix. To ensure the desired long-lasting visual appearance of decorative UHPC and reduce future maintenance costs, a time-effective strategy for creating a light-emitting biomimetic surface design was introduced. The samples exhibit high surface roughness, characterized by micro to nano-scale voids, displaying superhydrophobicity with contact angles reaching up to 155.45°. This is accompanied by roll-off angles decreasing to 7.1°, highlighting their self-cleaning features. The self-luminescence feature showcased intense initial light emission, offering a potential energy-efficient nighttime lighting solution.

A grapefruit microstructure fiber temperature sensor coated with liquid crystal based on waist-enlarged taper

A grapefruit microstructure fiber temperature sensor coated with liquid crystal based on waist-enlarged taper

Coordinated regulation for α-Al2O3 and mullite structures in the alumina-mullite fiber based on the different adding form of Fe element

The coordinated regulation for α-Al2O3 and mullite structures in the alumina-mullite duplex fiber poses a challenging yet crucial task in achieving a fiber with exceptional high-temperature properties. In this study, Fe element was added into the alumina-mullite fibers in the form of iron sol and ferric nitrate solution, respectively, with the aim of obtaining a fiber consisting of fine mullite grains embedded with nano α-Al2O3 grains. The results revealed that the addition of Fe element significantly enhances the crystallization process of mullite in alumina-mullite fibers. Specifically, adding iron sol resulted in the reduce of α-Al2O3 formation temperature to 1300 °C, while introducing Ferric nitrate solution promoted the formation of mullite phase. Simultaneous introduction of 1.3 wt% iron sol and 1.3 wt% Ferric nitrate solution contributed to achieve alumina-mullite fiber with tensile strength of 2.06 GPa. In addition, the influence mechanism of Fe source on the phase transformation and microstructures of alumina-mullite fiber were discussed.

Birefringence characterization in a dual-hole microstructured optical fiber using an OFDR method.

The birefringence in a dual-hole microstructured optical fiber is numerically calculated and characterized with an optical frequency domain reflectometry (OFDR) method. Due to the asymmetric dual air holes in the cross-section, the polarized L P01x and L P01y modes propagate with different group velocities and time delays. Through a polarized coherent OFDR system in experiment, the Fresnel reflection peaks for each mode are separated in the frequency domain with their corresponding beat frequency. Thus, the group birefringence -9.68×10-4 is calculated with a beat frequency difference of 50.03Hz between the L P01x and L P01y modes at a 6.2m fiber end, which is in good agreement with that of -9.54×10-4 from the theoretical simulation. Our demonstration provides an accurate and flexible method for group birefringence characterization in microstructured optical fibers with complex cross-sectional structures.

Dual transverse fiber tip Fabry-Perot cavities for simultaneous measurements of pressure and temperature

A fiber tip sensor based on dual transverse Fabry-Perot (FP) cavities for simultaneous temperature and gas pressure measurements is proposed, fabricated and tested. The proposed fiber tip sensor is formed by one-step polishing the end face of a microstructure fiber, which contains a hollow hole in the center and an eccentric core, to 45-degrees. The hybrid fiber tip sensor consists of a quartz cavity and a gas cavity effectively solving the problem of cross sensitivity in dual-parameter sensors. By tracking the shift of the interference spectra of the two FP cavities, simultaneous measurements of temperature and pressure is achieved. With advantages of a compact structure, high spatial resolution, simple fabrication and ability of multi-parameter detection, the sensor is suitable for use in a high temperature and high-pressure simultaneous sensing applications. Furthermore, the fabrication approach ensures consistent size of the FP cavities, making the sensor suitable for mass production.

Dimensions, microstructure, chemical, and hygroscopic analysis of steam-exploded bamboo fibers at different ages

Bamboo fibers (BFs) at different ages (1, 3, and 5 years old) were prepared by pretreatment and steam explosion. The results demonstrated that the separation degrees of BFs increased with the age of the bamboo. The combined effects of pretreatment and steam explosion partially removed the hemicellulose and lignin from BFs, while the crystalline structure of cellulose remained unaltered. The water vapor adsorption isotherms of BFs at different ages all showed a typical S-shape and could be classified as type II, and the hysteresis of BFs increased with the age of the bamboo. After pretreatment and steam explosion, the tissues in the vascular bundle were effectively crushed, and the parenchyma tissues were dislodged and separated from the fiber sheath. During the steam explosion process, hot steam penetrated the bamboo’s pores, including the pores induced by pretreatment. This caused fractures and delamination in the interface between the vascular bundle and the parenchyma tissues. These cracks progressed layer by layer along the vascular bundle interface, leading to the fracture of the bamboo.

Radiative cooling textiles using industry-standard particle-free nonporous micro-structured fibers

Abstract Thermal radiation is a major dissipative pathway for heat generated by the human body and offers a significant thermoregulation mechanism over a wide range of conditions. We could use this in garment design to enhance personal cooling, which can improve the wearing comfort of garments or even result in energy savings in buildings. At present, however, radiative cooling has received insufficient attention in commercial design and production of textiles for wearable garments. Textiles that efficiently transmit the radiative heat were recently demonstrated, but either do not utilize standard weaving and knitting processes for wearable garments or require substantial process modifications. Here, we demonstrate the design and implementation of large-scale radiative cooling textiles for localized cooling management and enhanced thermal comfort using industry-standard particle-free nonporous micro-structured fibers that are fully compatible with standard textile materials and production methods. The micro-structured fibers, yarns and fabrics are part of a hierarchical photonic structure design that renders the textiles highly infrared transparent (up to > 0.8) while assuring visual opacity (up to 0.99). We design radiative cooling textiles with first-principles electromagnetic methods and fabricate them using commercial textile materials and formation facilities. Our “fabless” approach is confirmed by very good quantitative agreement between design and measurements. The resulting fabrics exhibit wearability properties expected of wearable textiles, and lower skin temperature by ≥ 3 °C compared to conventional textiles, which offers the potential for > 30 % energy savings in buildings and increases wearing comfort by significantly reducing the reliance on latent heat dissipation for thermoregulation.

To What Extent Do Low-Voltage Electrostatic Fields Play a Role in the Physicochemical Properties of Pork during Freezing and Storage?

Low-voltage electrostatic fields (LVEF) are recognized as a new technology that can improve the quality of frozen meat. To determine the extent to which LVEF assistance affects the quality of frozen pork for long-term storage, pork was frozen and stored at -18 and -38 °C for up to 5 months. Water-holding capacity, muscle microstructure, and protein properties were investigated after up to 5 months of frozen storage with and without LVEF assistance. In comparison to traditional -18 and -38 °C frozen storage, LVEF treatment inhibited water migration during frozen storage and thawing. As a result, thawing losses were reduced by 15.97% (-18 °C) and 3.38% (-38 °C) in LVEF-assisted compared to conventional freezing methods. LVEF helped to maintain the muscle fiber microstructure and reduce muscle protein denaturation by miniaturizing ice crystal formation by freezing. As a result of this study, LVEF is more suitable for freezing or short-term frozen storage, while a lower temperature plays a more significant role in long-term frozen storage.

Generation of infrared photon pairs by spontaneous four-wave mixing in a CS2-filled microstructured optical fiber

We experimentally demonstrate frequency non-degenerate photon-pair generation via spontaneous four-wave mixing from a novel CS2-filled microstructured optical fiber. CS2 has high nonlinearity, narrow Raman lines, a broad transmission spectrum, and also has a large index contrast with the microstructured silica fiber. We can achieve phase matching over a large spectral range by tuning the pump wavelength, allowing the generation of idler photons in the infrared region, which is suitable for applications in quantum spectroscopy. Moreover, we demonstrate a coincidence-to-accidental ratio of larger than 90 and a pair generation efficiency of about 10-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-2}$$\\end{document} per pump pulse, which shows the viability of this fiber-based platform as a photon-pair source for quantum technology applications.

Transformation of traditional carbon fibers from microwaves reflection to efficient absorption via carbon fiber microstructure modulation

The high conductivity of commercial carbon fibers leads to a noticeable skinning effect and weak microwave impedance matching. This results in insufficient effective absorption bandwidth and less than ideal overall wave absorption performance, mainly reflecting electromagnetic waves. These limitations restrict the application of carbon fibers. In this study, we successfully prepared carbon fiber/epoxy composites with adjustable electrical conductivity by precisely controlling the temperature and time of pre-oxidized polyacrylonitrile (PAN) fibers during the low-temperature carbonization stage. This allowed us to regulate the components and microstructure of conductive carbon fibers. The carbon fiber/epoxy composites demonstrated exceptional microwave absorption performance due to their various loss mechanisms. The impedance matching conditions and microwave attenuation capability were also quantitatively evaluated. For 850-9 samples, an effective bandwidth of approximately 7 GHz (11 GHz–18 GHz) was achieved with a thickness of 2.5 mm. For 900-9 samples, the best reflection loss achieved is −39.9 dB at 5.8 GHz, which corresponds to a thickness of 3 mm. The carbon fibers with different electrical conductivity can be obtained by modulating the microstructure of carbon fibers, which can improve the impedance matching performance of conductive carbon fibers and reduce their reflection of electromagnetic waves to improve the microwave absorption performance, achieving the transformation of traditional carbon fibers from electromagnetic shielding to effective microwave absorption. This simple and efficient preparation method has yielded promising results and offers a new avenue for the advancement of high-performance carbon fiber microwave absorbing materials.

The mechanics of thin elastic sheet reinforced with fiber mesh subjected to combined flexure and extension

We present a three-dimensional continuum model aimed at investigating the mechanical performance of elastomeric materials reinforced with bidirectional fibers undergoing the combined out-of-plane bending moment and bilateral extension. To achieve this, we consider the Neo-Hookean strain energy model for the matrix material of the fiber composite and incorporate the strain energy of bidirectional fibers into the strain energy potential of the fiber composite. The bidirectional fibers’ strain energy is rigorously modeled by configuring the fiber kinematics on the fiber composite surface using differential geometry and accounting for stretching, bending, and twisting responses of the fibers via the computation of the first-order and second-order gradient of deformation. To establish equilibrium equations, we apply the variational principle to derive the constitutive relations, resulting in the normal and tangential shape equations of the fiber composite, and boundary conditions of bending and stretching. The model implementation emphasizes analyzing the combined out-of-plane bending and bilateral stretching effects on the fiber composite material, and the numerical results include the out-of-plane and in-plane deformation, strain-loading responses, bending, twisting, and stretching of fibers within the matrix material, as well as the deformation of the fiber network. Specifically, it is found that a larger bending moment results in intensified out-of-plane deformation while larger bilateral stretch decreases the out-of-plane deformation of fiber composite. In particular, bilateral stretches reduce the Lagrange strain (ɛ1) near the bilateral boundaries, unlike the intensity distribution of Lagrange strain (ɛ2) maintains almost unchanged due to no external tension applied on the upper and lower boundaries of the fiber while bending moments persist. These findings highlight the role of bilateral stretching acting as the prestress in reducing deflection, enhancing tensile strength and efficient use, and controlling crack generation of fiber-reinforced polymer (FRP) composites. More importantly, despite the scarcity of experimental data on fiber composite deformation at the microscopic, the theoretical demonstration of the extension and flexure of fiber units provide reasonable explanations for the resulting deformation of the overall fiber meshwork, validating the mechanism that the fiber microstructure deformation determines the overall deformation of fiber composites when subjected to combined bending moment and tension. Special attention should be given to the potential dislocation between the embedded meshwork and matrix material located in the center of the domain. Furthermore, the proposed model provides qualitatively reasonable explanations on the shaping of Bamboo Polylactic acid (PLA) composites, out-of-plane deformation of woven fabric, Sikken-type stiffener deformation, and fiber-reinforced thermoplastics via a series of numerical results.

Experimental and numerical analysis of the Microstructure and mechanical properties of unidirectional glass fiber reinforced epoxy composites

This paper proposes a numerical model to predict the pattern and features of the fracture surface and to understand the mechanisms and cause of the failure. Various fiber orientations of 0°, 90°, 0°/90° and ± 45° were utilized in the production of unidirectional glass-fiber-reinforced epoxy composites via the vacuum bagging technique. The mechanical properties of the manufactured composites were evaluated by measuring parameters including tensile strength, compressive strength, flexural strength and interlaminar shear strength. High-resolution scanning electron microscopy was used to examine the mechanisms of fracture in laminates. The mechanical properties of the composite material were found to be considerably improved when a unidirectional 0° fiber orientation was used, as compared to other fiber orientations. This was true for tensile, compressive, flexural and interlaminar shear loading modes. The composite laminates demonstrated several modes of breaking, including fibers pulling away from the matrix, holes in the matrix and river flow lines, depending on the direction of the fibers. The outcomes of the numerical simulation demonstrate a high level of fidelity with experimental findings. This study provides a valuable reference for predicting numerical analysis of the microstructure and mechanical properties.

Effect of gradual thermoforming pressure on the mechanical properties of jute/polypropylene commingled composites

The present work presents a new approach to the parameters of the thermoforming process for jute fiber commingled thermoplastic composites based on pressure control. Effect of gradual pressure on the microstructures of jute fiber and their mechanical properties has been investigated. The singeing of Jute yarn and subsequent co-twisting with Polypropylene (PP) was done to make reinforcement. Jute/PP composites were developed using Jute/PP commingled reinforcement. Flexural and Charpy impact tests were conducted to analyze the mechanical performance of composites made using gradual and instant loading on the compression hot press. It is found that application of gradual pressure not only decreases fiber damages, but also increase flexural strength by 82%, impact strength by 43% and impact energy by 93% as compared to composite fabricated using instant pressure. Further, the complete analysis of microstructure of fibers of both type of composites is done to compare the effect of both fabrication techniques.

Super-elastic microstructured triboelectric fibers and textiles fabricated by extrusion and thermal drawing for smart-home applications

Flexible and wearable textile-based triboelectric nanogenerators (TENGs) have attracted extensive attention in wearable electronics owing to their ability to convert waste mechanical energy from human motion into electrical energy. However, the performances of TENGs are lower than those of planar/film configurations due to the complex fiber fabrications and limited mechanical freedom. In this work, we demonstrate an extrusion method combined with thermal drawing (ETD method) for continuous and scalable triboelectric fiber fabrication, providing longitudinal uniform fibers for hundreds of kilometers. Based on the ETD method, super-elastic microstructured triboelectric fibers (SMTFs) were fabricated, consisting of hollow elastomeric and liquid metal cores (EGaIn). The SMTFs showed excellent superelasticity with clear and uniform microstructures. The fibers could withstand strain up to 1800% and exhibited excellent electrical output performance. Utilizing a single fiber as the medium for triboelectric energy collection, the average open circuit voltage and instantaneous power density are respectively up to 210 V/m and 21 μW/m with a 40 MΩ external load resistance. The SMTFs could also be woven into deformable textiles with high electrical outputs up to 160 V, 10 μA, and 50 nC. In addition, the SMTFs-based textiles were further demonstrated as completely soft and stretchable components for self-powered sensing in smart home applications.

Influence of Electrospinning Parameters on the Morphology of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fibrous Membranes and Their Application as Potential Air Filtration Materials.

A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Polyhydroxyalkonates (PHAs) are receiving increasing attention because of the unique biodegradability and biocompatibility they offer. However, the applications of PHAs are still limited due to high production costs and insufficient study. This project examines the optimal electrospinning parameters for the production of PHA-based fibrous membranes for air filtration. A common biodegradable polyester, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was electrospun into a nanofibrous membrane with a well-controlled surface microstructure. In order to produce smooth, bead-free fibers with micron-scale diameters, the effect of the process parameters (applied electric field, solution flow rate, inner diameter of hollow needle, and polymer concentration) on the electrospun fiber microstructure was optimized. The well-defined fibrous structure was optimized at an applied electric field of 20 kV, flow rate of 0.5 mL/h, solution concentration of 12 wt.%, and needle inner diameter of 0.21 mm. The morphology of the electrospun PHBV fibrous membrane was observed by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) and Raman spectroscopy were used to explore the chemical signatures and phases of the electrospun PHBV nanofiber. The ball burst strength (BBS) was measured to assess the mechanical strength of the membrane. The small pore size of the nanofiber membranes ensured they had good application prospects in the field of air filtration. The particle filtration efficiency (PFE) of the optimized electrospun PHBV fibrous membrane was above 98% at standard atmospheric pressure.

Tensile failure mechanisms investigation of mesophase pitch-based carbon fibers based on continuous defective graphene nanoribbon model

Mesophase pitch (MPP)-based carbon fibers exhibit outstanding mechanical properties, notably an exceptionally high Young’s modulus. Despite extensive investigations into the microstructure of MPP-based carbon fibers, the influence of these factors on deformation mechanisms under tension remains unclear. This study employs the continuous defective graphene nanoribbons (dGNR) atomistic structure model for molecular dynamics simulations to explore the tensile failure mechanisms of MPP-based carbon fibers. In the simulation model, the structure of the defective region was generated through high-temperature annealing, and a transition region was introduced to prevent distortion and damage to the active graphene edges. The simulation reveals the evolutionary process of the microstructure of MPP-based carbon fibers under tension and achieves Young’s modulus predictions with greater accuracy than theoretical models. Additionally, the study shows that different strengths of interactions between adjacent graphene nanoribbons can lead to two distinct failure modes. Models with larger crystallite dimensions along the fiber axis and lower average defective concentrations exhibit geometric deformation coordination between adjacent nanoribbons, potentially elucidating the increasing strength trend in MPP-based carbon fibers with rising graphitization levels. Our simulations provide insights into the tensile failure mechanisms of MPP-based carbon fibers, offering valuable guidance for regulating their microstructure to enhance mechanical performance.