Fibers, Volume 6, Issue 2 (June 2018) – 25 articles

Optimal suppression of higher-order modes (HOMs) in hollow-core antiresonant fibers comprising a single ring of thin-walled capillaries was previously studied, and can be achieved when the condition on the capillary-to-core diameter ratio is satisfied ($d/D\approx 0.68$). Here we report on the conditions for maximizing the leakage losses of HOMs in hollow-core nested antiresonant node-less fibers, while preserving low confinement loss for the fundamental mode. Using an analytical model based on coupled capillary waveguides, as well as full-vector finite element modeling, we show that optimal $d/D$ value leading to high leakage losses of HOMs, is strongly correlated to the size of nested capillaries. We also show that extremely high value of degree of HOM suppression (∼1200) at the resonant coupling is almost unchanged on a wide range of nested capillary diameter $d_{Nested}$ values. These results therefore suggest the possibility of designing antiresonant fibers with nested elements, which show optimal guiding performances in terms of the HOM loss compared to that of the fundamental mode, for clearly defined paired values of the ratios $d_{Nested}/d$ and $d/D$. These can also tend towards a single-mode behavior only when the dimensionless parameter $d_{Nested}/d$ is less than 0.30, with identical wall thicknesses for all of the capillaries. Full article

Touch-sensitive electrical arrays are the primary user interface for modern consumer electronics. Most contemporary touch sensors, including known iterations of textile-based touch sensors, function by detecting capacitive changes within a circuit resulting from direct skin contact. However, this method of operation fails when the user’s skin or the surface of the touch sensor is dirty, oily or wet, preventing practical use of textile-based touch sensors in real-world scenarios. Here, an electrically touch-responsive woven textile is described, which is composed of fluoropolymer-wrapped conductive threads. The fluoropolymer wrapping prevents contaminant buildup on the textile surface and also electrically insulates the conductive thread core. The woven textile touch sensor operates via surface potential changes created upon skin contact. This method of operation, called the triboelectric effect, has not been widely used to create textile touch sensors, to date. The influences of surface wetness and varying skin surface chemistry are studied, and the triboelectric textile touch sensors are found to be advantageously insensitive to these environmental variables, indicating that triboelectric textiles have promise for practical use as touch interfaces in furniture and interior design. Full article

Thermoplastic starch (TPS) reinforced by 1 wt % nanofiber cellulose (NFC) reinforcing from water hyacinth was produced. Ultrasonic vibration time (UVT) was applied to bionanocomposites during gelation for 0, 15, 30 and 60 min. Morphology of the NFC was investigated using Transmission Electron Microscopy (TEM). Scanning Electron Microscopy (SEM) and tensile tests were performed to identify the fracture surface and determine the mechanical properties of the bionanocomposites, respectively. The Crystallinity index (CI) of untreated and treated bionanocomposites was measured using X-ray Diffraction (XRD). The average diameter of NFC water hyacinth was 10–20 nm. The maximum tensile strength (TS) and modulus elasticity (ME) of the bionanocomposite was 11.4 MPa and 443 MPa respectively, after 60 min UVT. This result was supported by SEM which indicated good dispersion and compact structure. Full article

Revolver optical fibers (RF) are special type of hollow-core optical fibers with negative curvature of the core-cladding boundary and with cladding that is formed by a one ring layer of capillaries. The physical mechanisms contributing to the waveguiding parameters of RFs are discussed. The optical properties and possible applications of RFs are reviewed. Special attention is paid to the mid-IR hydrogen Raman lasers that are based on RFs and generating in the wavelength region from 2.9 to 4.4 μm. Full article

This paper deals with behavior of concrete’s compressive and bending strengths with the addition of high amount of polyolefin macro fibers. Polyolefin fiber is used to increase the bending strength and compressive strength, these experiments are done to investigate the cracking behavior and found the bending strength and compressive strength of polyolefin fiber reinforced concrete. Normally, concrete is mixed with various amount of fiber, but in this experiment five different specimens were prepared, S-1 is without fiber; S-2, homogeneous mixing of fiber volume of 10 kg/m³; S-3, homogeneous mixing of fiber volume of 25 kg/m³; S-4, homogeneous mixing of fiber volume of 35 kg/m³; and S-5, which contains 25 kg/m³ fiber mixed by hand in three different layers. A small amount of fly ash (18.18% of cement mass) is also mixed in the concrete specimens for better results. Concrete specimens were tested on 7th day and 28th day of the curing process. Water absorption capacity and compressive strength tests were done in the dry state and wet state to find the strength difference. More than 50% of flexural strength was gained on the 28th day of the destructive test. Post-cracking behavior was observed on the 28th day of the test, the specimens with fiber content were found to take load after cracking and hold more load to failure. Full article

Polymer nanofibres are created from many different techniques, with varying rates of production. Rotary jet spinning is a relatively new technique for making nanofibres from both polymer solutions and melt. With electrospinning being by far the most widespread processing method for polymer nanofibres, we performed a direct comparison of polyamide 6 (PA6) nanofibre production between these two methods. It was found that electrospinning produced slightly smaller-diameter fibres, which scaled with a decrease in solution viscosity. In comparison, rotary jet spun fibres could be produced from a reduced range of polymer concentrations and exhibited therefore slightly larger diameters with greater variation. Crystallinity of the fibres was also compared between the two techniques and the bulk polymer, which showed a decrease in crystallinity compared to bulk PA6. Full article

Multilayered coatings deposited using the layer-by-layer (LbL) assembly technique have attracted great interest in recent years as a sustainable and efficient solution for conferring flame retardant properties to fabrics. The unique structure and interaction established upon the coating assembly are the key factors for successful flame retardant properties. In this study we aimed at the deposition of multilayered coatings comprising chitosan and montmorillonite with a LbL-like structure and interactions by the simple processing of compacted chitosan/montmorillonite complexes obtained by the direct mixing of an oppositely charged solution/suspension. Upon drying, the prepared complex yielded a continuous coating characterized by a brick-and-mortar multi-layered structure, in which oriented clay nanoplatelets were held together by a continuous chitosan matrix. When deposited on acrylic fabrics these coatings were able to suppress the melt-dripping phenomenon, and at 10 and 20% add-ons achieved self-extinguishing behavior within a few seconds after ignition. Cone calorimetry testing revealed an increase in time to ignition (up to +46%) and considerable reductions of the rates at which heat is released (up to −62 and −49% for peak of heat release rate and total heat release, respectively). A reduction in the total smoke release (up to −49%) was also observed. Full article

A goal in the field of wearable technology is to blend electronics with textile fibers to create garments that drape and conform as normal, with additional functionality provided by the embedded electronics. This can be achieved with electronic yarns (E-yarns), in which electronics are integrated within the fibers of a yarn. A challenge is incorporating non-stretch E-yarns with stretch fabric that is desirable for some applications. To address this challenge, E-yarns containing LEDs were embroidered onto the stretch fabric of a unitard used as part of a carnival costume. A zig-zag pattern of attachment of E-yarns was developed. Tensile testing showed this pattern was successful in preventing breakages within the E-yarns. Use in performance demonstrated that a dancer was unimpeded by the presence of the E-yarns within the unitard, but also a weakness in the junctions between E-yarns was observed, requiring further design work and reinforcement. The level of visibility of the chosen red LEDs within black E-yarns was low. The project demonstrated the feasibility of using E-yarns with stretch fabrics. This will be particularly useful in applications where E-yarns containing sensors are required in close contact with skin to provide meaningful on-body readings, without impeding the wearer. Full article

Textiles have been at the heart of human technological progress for thousands of years, with textile developments closely tied to key inventions that have shaped societies. The relatively recent invention of electronic textiles is set to push boundaries again and has already opened up the potential for garments relevant to defense, sports, medicine, and health monitoring. The aim of this review is to provide an overview of the key innovative pathways in the development of electronic textiles to date using sources available in the public domain regarding electronic textiles (E-textiles); this includes academic literature, commercialized products, and published patents. The literature shows that electronics can be integrated into textiles, where integration is achieved by either attaching the electronics onto the surface of a textile, electronics are added at the textile manufacturing stage, or electronics are incorporated at the yarn stage. Methods of integration can have an influence on the textiles properties such as the drapability of the textile. Full article

The capacity to load bacteriophages into electrospun nanofibers of two representative biocompatible polymers has been evaluated, paying special attention to the possibility of preserving their antibacterial activity. Specifically, the work involves the following steps: (a) Evaluation of the effect of the applied electrical field on the phage activity; (b) evaluation of the activity when a lyophilization process could be avoided by using water soluble polymers (e.g., poly(ethylene glycol); (c) evaluation of the activity when dissolution of the polymer requires an organic solvent and lyophilization is theoretically necessary. In this case, a poly(ester urea) (PEU) derived from the natural L-leucine amino acid has been considered. Adsorption of commercial bacteriophage preparations into calcium carbonate particles was demonstrated to be a promising methodology to avoid lyophilization and keep the initial bactericide activity at a maximum. Phagestaph and Fersis bacteriophage commercial preparations have been selected for this study due to their specific activity against Staphylococci (e.g., S. aureus) and Streptococci (e.g., S. pyogenes) bacteria. Adhesion and proliferation assays using epithelial cells demonstrated the biocompatibility of both unloaded and bacteriophage-loaded PEU scaffolds, although some slight differences were observed depending on the type of bacteriophage and the selected preparation methodology. Full article

Four-wave mixing in optical fibers has been proven to have many applications within processing of classical optical signals. In addition, recent developments in multimode fibers have made it possible to achieve the necessary phase-matching for efficient four-wave mixing over a very wide bandwidth. Thus, the combination of multimode fiber optics and four-wave mixing is very attractive for various applications. This is especially the case for applications in quantum communication, for example in photon-pair generation. This is the subject of this work, where we discuss the impact of fluctuations in core radius on the quality of the heralded single-photon states and demonstrate experimental results of intermodal spontaneous four-wave mixing for photon-pair generation. Full article

Conventional flame retardant (FR) application processes for textiles involve aqueous processing which is resource-intensive in terms of energy and water usage. Recent research using sol-gel and layer-by-layer chemistries, while claimed to be based on more environmentally sustainable chemistry, still require aqueous media with the continuing problem of water management and drying processes being required. This paper outlines the initial forensic work to characterise commercially produced viscose/flax, cellulosic furnishing fabrics which have had conferred upon them durable flame retardant (FR) treatments using a novel, patented atmospheric plasma/Ultraviolet (UV) excimer laser facility for processing textiles with the formal name Multiplexed Laser Surface Enhancement (MLSE) system. This system (MTIX Ltd., Huddersfield, UK) is claimed to offer the means of directly bonding of flame retardant precursor species to the component fibres introduced either before plasma/UV exposure or into the plasma/UV reaction zone itself; thereby eliminating a number of wet processing cycles. Nine commercial fabrics, pre-impregnated with a semi-durable, proprietary FR finish and subjected to the MLSE process have been analysed for their flame retardant properties before and after a 40 °C 30 min water soak. For one fabric, the pre-impregnated fabric was subjected to a normal heat cure treatment which conferred the same level of durability as the plasma/UV-treated analogue. Thermogravimetric analysis (TGA) and limiting oxygen index (LOI) were used to further characterise their burning behaviour and the effect of the treatment on surface fibre morphologies were assessed. Scanning electron microscopy indicated that negligible changes had occurred to surface topography of the viscose fibres occurred during plasma/UV excimer processing. Full article

There are currently still some sustainability-related issues that need to be tackled within the construction sector. Namely, cement production is accountable for nearby 5% of the worldwide total CO₂-eq release. Therefore, environmentally viable and economically sustainable solutions need to be pursued in order to mitigate the use of Portland cement. The incorporation of industrial waste in concrete compositions, such as fly ash (from coal combustion in power stations) is a feasible alternative. The properties of these residues may be enhanced through alkaline activation, which is able to yield aluminosilicate-based materials with excellent physico-chemical properties. Nonetheless, these materials exhibit a brittle behaviour. Therefore, the present work addresses the study of alkali-activated composites reinforced with sisal fibres. For that purpose, alkali-activated Class F fly ash was mixed with natural fibres and the composite mechanical behaviour was assessed through both indirect tensile and compressive tests. Four different fibre contents, in wt % of fly ash (0, 0.2, 0.6 and 1%), two fibre lengths (13 and 50 mm) and four curing periods (14, 28, 56 and 112 days) were considered. Results confirm that the post-cracking response of these composites was improved with the inclusion of sisal fibres. In general, higher residual tensile strengths and dissipated energy were observed for the lengthier fibres, i.e., 50 mm. Full article

Studies on dietary fiber and nutrient bioavailability have gained an increasing interest in both human and animal nutrition. Questions are increasingly being asked regarding the faith of nutrient components such as proteins, minerals, vitamins, and lipids after feed formulation. The aim of this review is to evaluate the evidence with the perspective of fiber usage in feed formulation. The consumption of dietary fiber may affect the absorption of nutrients in different ways. The physicochemical factors of dietary fiber, such as fermentation, bulking ability, binding ability, viscosity and gel formation, water-holding capacity and solubility affect nutrient absorption. The dietary fiber intake influences the different methods in which nutrients are absorbed. The increase in the total fiber content of the diet may delay the glycemic response. Soluble fiber decreased blood glucose content whereas purified insoluble fiber has a little or no effect on the blood glucose levels after a meal. Dietary fiber and prebiotics influence the host animal well-being by regulating blood glucose or insulin levels, stool bulking effects, increasing the acidity of the gut, constructive synthesis of short chain fatty acids (SCFAs), decreasing intestinal transit time, stimulating the growth of intestinal microbes, and increasing blood parameters. Previous studies suggest that fiber affects the bioavailability of nutrients, and maintains the host wellness. Full article

In this study, the isolation and characterization of nanocellulose from pineapple leaf fibers (PLF) were carried out. Chemical pretreatment included pulping, bleaching, and acid hydrolysis to remove lignin, hemicellulose, and extractive substances were conducted. This was followed by high-shear homogenization and ultrasonication to produce nanocellulose. Morphological changes to the PLF due to treatment were investigated using scanning electron microscopy (SEM). This showed that the PLF had a diameter of 1–10 µm after high-shear homogenizing. Transmission electron microscopy (TEM) indicated that the nanofibers after ultrasonication for 60 min showed 40–70 nm diameters. Particle size analysis (PSA) indicates that the fibers had an average diameter of 68 nm. Crystallinity index was determined by X-ray diffraction (XRD) and had the highest value after acid hydrolysis at 83% but after 60 min ultrasonication, this decreased to 62%. Meanwhile, Fourier transform infrared (FTIR) spectroscopy showed there was no chemical structure change after acid hydrolysis. The most significant finding from thermal gravimetric analysis (TGA) is that the higher degradation temperature of nanofibers indicates superior thermal stability over untreated fiber. These results indicate that PLF waste could become a viable source of commercially valuable nanocellulose. Full article

Textile hemp (Cannabis sativa L.) is a multipurpose crop producing biomass with uses in e.g., the textile, biocomposite, and construction sectors. It was previously shown that the hypocotyl of hemp is useful to study the kinetics of secondary tissue development, where primary and secondary growths are temporally uncoupled. We here sought to demonstrate that the stem of adult hemp plants is an additional suitable model to study the heterogeneous lignification of the tissues and the mechanisms underlying secondary cell wall formation in bast fibres. A targeted quantitative PCR analysis carried out on a set of twenty genes involved in cell wall biosynthesis clearly showed differences in expression in the core and cortical tissues along four stem regions spanning from elongation to cell wall thickening. Genes involved in phenylpropanoid biosynthesis and secondary cell wall cellulose synthases were expressed at higher levels in core tissues at the bottom, while specific genes, notably a class III peroxidase and a gene partaking in lignan biosynthesis, were highly expressed in the cortex of elongating internodes. The two systems, the hypocotyl and the adult stem of textile hemp, are equally valid and complementary to address questions related to lignification and secondary cell wall deposition. Full article

Lignocellulosic composite (LC) panels were fabricated using an adhesive matrix prepared from three different agricultural by-products: dried distillers grains with solubles (DDGS), pennycress (Thlaspi arvense L.) press cake (PPC), or lesquerella [Lesquerella fendleri (A. Gary) S. Watson] press cake (LPC) reinforced with Paulownia elongata L. wood (PW) particles. The goal in this study was to assess the mechanical properties of composites utilizing these low-cost matrix materials, which were subjected to various oil extraction methods. Three types of oil extraction methods were utilized: ethanol, supercritical CO₂, and hexane, in order to generate matrix materials. These matrix materials were mixed with equal proportions of PW and hot pressed to generate panels. Overall, hexane extraction was the best method to enhance the mechanical properties of the matrices used to fabricate lignocellulosic composites. LPC’s produced a matrix that gave the resulting composite superior flexural properties compared to composites generated from DDGS and PPC matrices. The mechanical properties of composites generated from soy products (soybean meal flour or soy protein isolate) were similar to those derived from DDGS, PPC, or LPC. The dimensional stability properties of LCs were improved when the hexane extraction method was employed, unlike with the other extraction methods that were used to generate matrices. Full article

This paper presents the progress in the fields of the modelling and design of lanthanide ion-doped chalcogenide glass fiber lasers. It presents laser cavity designs that have been developed in order to optimize the performance of lanthanide ion-doped chalcogenide glass fiber lasers. Additionally, various numerical algorithms that have been applied for the optimization of chalcogenide glass lasers are reviewed and compared. The comparison shows that a combination of less accurate but more robust algorithms with more accurate ones gives the most promising performance. Full article

A method for fabricating robust and thin hollow-core optical fibers that carry mid-infrared light is proposed for use in endoscopic laser applications. The fiber is made of stainless steel tubing, eliminating the risk of scattering small glass fragments inside the body if the fiber breaks. To reduce the inner surface roughness of the tubing, a polymer base layer is formed prior to depositing silver and optical-polymer layers that confine light inside the hollow core. The surface roughness is greatly decreased by re-coating thin polymer base layers. Because of this smooth base layer surface, a uniform optical-polymer film can be formed around the core. As a result, clear interference peaks are observed in both the visible and mid-infrared regions. Transmission losses were also low for the carbon dioxide laser used for medical treatments as well as the visible laser diode used for an aiming beam. Measurements of bending losses for these lasers demonstrate the feasibility of the designed fiber for endoscopic applications. Full article

Composite fibers and films based on cellulose and betulin were spun for the first time from solutions in N-methylmorpholine-N-oxide using the dry–wet jet method. The rheological properties of the composite solutions did not reveal any fundamental difference from those of the cellulose solutions. Introduction of betulin into the cellulose matrix (up to 10%) led to a decrease in the mechanical properties of the obtained fibers. The structure of the composite fibers was analyzed using SEM and X-ray diffraction methods. It was shown that the introduction of an additive into the cellulose matrix led to a decrease in the structural ordering of the cellulose. Comparative studies of the antibacterial activity of the composite films on Escherichia coli (E. coli) were carried out. The antifungal activity of the composite films was estimated using the strain of the O-97 Trichoderma viride Pers ex Fr (Gause Institute of New Antibiotics, Moscow, Russia). Full article

A post-esterification with a high degree of substitution (hDS) mechanical treatment (Pe(hDS)M) approach was used for the production of highly hydrophobic cellulose nanoparticles (CNPs). The process has the advantages of substantially reducing the mechanical energy input for the production of CNPs and avoiding CNP aggregation through drying or solvent exchange. A conventional esterification reaction was carried out using a mixture of acetic anhydride, acetic acid, and concentrated sulfuric acid, but at temperatures of 60–85 °C. The successful hDS esterification of bleached eucalyptus kraft pulp fibers was confirmed by a variety of techniques, such as Fourier transform infrared (FTIR), solid state ¹³C NMR, X-ray photoelectron spectroscopy (XPS), elemental analyses, and X-ray diffraction (XRD). The CNP morphology and size were examined by atomic force microscopy (AFM) as well as dynamic light scattering. The hydrophobicity of the PeM-CNP was confirmed by the redispersion of freeze-dried CNPs into organic solvents and water contact-angle measurements. Finally, the partial conversion of cellulose I to cellulose II through esterification improved PeM-CNP thermal stability. Full article

Collagen plays a major role in providing mechanical support within the extracellular matrix and thus has long been used for various biomedical purposes. Exemplary, it is able to replace damaged tissues without causing adverse reactions in the receiving patient. Today’s collagen grafts mostly are made of decellularized and otherwise processed animal tissue and therefore carry the risk of unwanted side effects and limited mechanical strength, which makes them unsuitable for some applications e.g., within tissue engineering. In order to improve collagen-based biomaterials, recent advances have been made to process soluble collagen through nature-inspired silk-like spinning processes and to overcome the difficulties in providing adequate amounts of source material by manufacturing collagen-like proteins through biotechnological methods and peptide synthesis. Since these methods also open up possibilities to incorporate additional functional domains into the collagen, we discuss one of the best-performing collagen-like type of proteins, which already have additional functional domains in the natural blueprint, the marine mussel byssus collagens, providing inspiration for novel biomaterials based on collagen-silk hybrid proteins. Full article

Plant fibers find wide application in various fields that demand specific parameters of fiber quality. To develop approaches for the improvement of yield and quality of bast fibers, the knowledge of the fiber developmental stages and of the key molecular players that are responsible for a certain parameter, are vitally important. In the present review the key stages of fiber development, such as initiation, intrusive growth, and formation of thickened cell wall layers (secondary and tertiary cell walls) are considered, as well as the impact of each of these stages on the final parameters of fiber yield and quality. The problems and perspectives of crop quality regulation are discussed. Full article

This paper aims to investigate the effect of adding carbon nanotubes (CNTs) on the durability of latex modified mortar (LMM). Up to 2.5% of CNTs by wt. of styrene-butadiene latex (SBR latex) CNTs were added to latex modified mortar (LMM) specimens before they are subjected to two different thermal tests: freeze-thaw and thermal fatigue. LMM specimens were subjected to a number of freeze-thaw cycles according to American Society for Testing and Materials (ASTM) C-666 in order to simulate winter outdoor conditions in the United States (US) northern areas. Also, the specimens were subjected to thermal fatigue cycles similar to summer outdoor conditions. A large number of specimens were prepared in cubes, cylinders, and prisms, and were mechanically tested in compression, splitting tension, and flexure in order to evaluate the LMM specimens after the thermal exposure. Compression and tension specimens were tested after 50% and after 100% of the total number of cycles in order to assess the effect of the number of cycles on the mechanical performance. For LMM prims, dimensional stability was assessed first by monitoring the development of shrinkage strains during the application of thermal cycles. The LMM prisms were then tested in flexure after the completion of all the thermal cycles. The effectiveness of adding CNTs was evaluated by comparing between the performance of control LMM specimens and those with different CNTs contents. CNTs were found to alter the compressive strength, tensile strength, and flexural load carrying capacity of LMM specimens. Full article

Accumulating evidence has suggested the effects of a higher dietary fiber intake on weight loss and reduced inflammation. In line with this, recent observations presented higher consumption of dietary fiber in relation to the lower risks of symptomatic knee osteoarthritis and worsening knee pain. Because both obesity and inflammation are commonly linked with knee osteoarthritis and rheumatoid arthritis, and preliminary results have suggested a role of microbiome in both joint disorders, we hypothesized that increased dietary fiber intakes might confer benefits in reducing the risk of rheumatoid arthritis and/or delaying disease progression. In this commentary, we sought to provide rationales regarding fiber’s physiological characteristics and its influence in the gut microbiome to postulate a potential link between fiber intake and the risk of rheumatoid arthritis. Verification of these hypotheses requires data from observational and experimental studies. Full article