Scalable One-Step Wet-Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micrometer-dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO “inks” in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non-solvent precipitation, dispersion destabilization, ionic cross-linking, and polyelectrolyte complexation. One-step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post-treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials.

Knitted strain sensor textiles of highly conductive all-polymeric fibers

A scaled-up fiber wet-spinning production of electrically conductive and highly stretchable PU/PEDOT:PSS fibers is demonstrated for the first time. The PU/PEDOT:PSS fibers possess the mechanical properties appropriate for knitting various textile structures. The knitted textiles exhibit strain sensing properties that were dependent upon the number of PU/PEDOT:PSS fibers used in knitting. The knitted textiles show sensitivity (as measured by the gauge factor) that increases with the number of PU/PEDOT:PSS fibers deployed. A highly stable sensor response was observed when four PU/PEDOT:PSS fibers were co-knitted with a commercial Spandex yarn. The knitted textile sensor can distinguish different magnitudes of applied strain with cyclically repeatable sensor responses at applied strains of up to 160%. When used in conjunction with a commercial wireless transmitter, the knitted textile responded well to the magnitude of bending deformations, demonstrating potential for remote strain sensing applications. The feasibility of an all-polymeric knitted textile wearable strain sensor was demonstrated in a knee sleeve prototype with application in personal training and rehabilitation following injury.

Image processing and pattern recognition in textiles

Image processing and pattern recognition have been successfully applied in many textile related areas. For example, they have been used in defect detection of cotton fibers and various fabrics. In this work, the application of image processing into animal fiber classification is discussed. Integrated into / with artificial neural networks, the image processing technique has provided a useful tool to solve complex problems in textile technology. Three different approaches are used in this work forfiber classification and pattern recognition: feature extraction with image process, pattern recognition and classification with artificial neural networks, and feature recognition and classification with artificial neural network. All of them yieldssatisfactory results by giving a high level of accuracy in classification.

Nanoparticle coatings for UV protective textiles

As the intensity of UV radiation increases every year, effective methods to block UV rays to protect human skin, plastics, timber and other polymer materials are urgently sought. Textiles serve as important materials for UV protection in many applications. The utilisation of nanoparticles to textile materials has been the object of several studies aimed at producing finished fabrics with different performances. This article reviews the recent advancement in the field of UV blocking textiles and fibers that are functionalised with nanostructured surface coatings. Different types of UV blocking agents are discussed and various examples of UV blocking textiles utilising ZnO and TiO₂ are presented. Future challenges such as wash-fastness and photocatalysis are also discussed.

Novel immobilization of a quaternary ammonium moiety on keratin fibers for medical applications.

This paper introduces a new approach for immobilizing a quaternary ammonium moiety on a keratinous substrate for enhanced medical applications. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in the keratin, followed by reaction with [2-(acryloyloxy)ethyl]trimethylammonium chloride through thiol-ene click chemistry. The modified substrate was characterized with Raman and infrared spectroscopy, and assessed for its antibacterial efficacy and other performance changes. The results have demonstrated that the quaternary ammonium moiety has been effectively attached onto the keratin structure, and the resultant keratin substrate exhibits a multifunctional effect including antibacterial and antistatic properties, improved liquid moisture management property, improved dyeability and a non-leaching characteristic of the treated substrate.

Strain-responsive polyurethane/PEDOT:PSS elastomeric composite fibers with high electrical conductivity

It is a challenge to retain the high stretchability of an elastomer when used in polymer composites. Likewise, the high conductivity of organic conductors is typically compromised when used as filler in composite systems. Here, it is possible to achieve elastomeric fiber composites with high electrical conductivity at relatively low loading of the conductor and, more importantly, to attain mechanical properties that are useful in strain-sensing applications. The preparation of homogenous composite formulations from polyurethane (PU) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) that are also processable by fiber wet-spinning techniques are systematically evaluated. With increasing PEDOT:PSS loading in the fiber composites, the Young's modulus increases exponentially and the yield stress increases linearly. A model describing the effects of the reversible and irreversible deformations as a result of the re-arrangement of PEDOT:PSS filler networks within PU and how this relates to the electromechanical properties of the fibers during the tensile and cyclic stretching is presented. Conducting elastomeric fibers based on a composite of polyurethane (PU) and PEDOT:PSS, produced by a wet-spinning method, have high electrical conductivity and stretchability. These fibers can sense large strains by changes in resistance. The PU/PEDOT:PSS fiber is optimized to achieve the best strain sensing. PU/PEDOT:PSS fibers can be produced on a large scale and integrated into conventional textiles by weaving or knitting. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrafine PDMS fibers: Preparation from in situ curing-electrospinning and mechanical characterization

Polydimethylsiloxane (PDMS) fibers with unexpected elasticity were prepared by a modified core-shell electrospinning method using a commercially-available liquid PDMS precursor (Sylgard 184) and polyvinylpyrrolidone (PVP) as core and sheath materials, respectively. The liquid PDMS precursor was crosslinked in situ to form a solid core when the newly-electrospun core-sheath nanofibers were deposited onto a hot-plate electrode collector. After dissolving the PVP sheath layer off the fibers, net PDMS fibers showed larger average diameter than core-sheath fibers, with an average diameter around 1.35 μm. The tensile properties of both single fibers and fibrous mats were measured. Single PDMS fibers had a tensile strength and elongation at break of 6.0 MPa and 212%, respectively, which were higher than those of PDMS cast film (4.9 MPa, 93%). The PDMS fiber mat had larger elongation at break than the single PDMS fibers, which can be drawn up to 403% their original length. Cyclic loading tests indicated a Mullin effect on the PDMS fiber mats. Such a superior elastic feature was attributed to the PDMS molecular orientation within fibers and the randomly-orientated fibrous structure. Highly-elastic, ultrafine PDMS fibers may find applications in strain sensors, biomedical engineering, wound healing, filtration, catalysis, and functional textiles. © The Royal Society of Chemistry 2014.

High-performance multifunctional graphene yarns: toward wearable all-carbon energy storage textiles

The successful commercialization of smart wearable garments is hindered by the lack of fully integrated carbon-based energy storage devices into smart wearables. Since electrodes are the active components that determine the performance of energy storage systems, it is important to rationally design and engineer hierarchical architectures atboth the nano- and macroscale that can enjoy all of the necessary requirements for a perfect electrode. Here we demonstrate a large-scale flexible fabrication of highly porous high-performance multifunctional graphene oxide (GO) and rGO fibers and yarns by taking advantage of the intrinsic soft self-assembly behavior of ultralarge graphene oxide liquid crystalline dispersions. The produced yarns, which are the only practical form of these architectures for real-life device applications, were found to be mechanically robust (Young's modulus in excess of 29 GPa) and exhibited high native electrical conductivity (2508 ± 632 S m(-1)) and exceptionally high specific surface area (2605 m(2) g(-1) before reduction and 2210 m(2) g(-1) after reduction). Furthermore, the highly porous nature of these architectures enabled us to translate the superior electrochemical properties of individual graphene sheets into practical everyday use devices with complex geometrical architectures. The as-prepared final architectures exhibited an open network structure with a continuous ion transport network, resulting in unrivaled charge storage capacity (409 F g(-1) at 1 A g(-1)) and rate capability (56 F g(-1) at 100 A g(-1)) while maintaining their strong flexible nature.

UV protection performance of textiles affected by fiber cross-sectional shape

Abstract
In this study, a model was set up for simulating the effects of varying fiber cross-sectional shapes on ultraviolet protection of fibers. The fiber diameter and fiber type were also involved in the model setting. Experiments of diffuse reflectance spectra measurement on natural (wool, cotton, silk), regenerated (bamboo viscose) and synthetic (polyester, nylon) fibers were conducted to verify the model predicted results. When a more complex shape was assumed as the fiber cross-section for model calculation, the predicted results have a better agreement with the actual results. The effects on ultraviolet absorption from fibers with different cross-sectional shapes were investigated at a single fiber, fiber bundle and yarn levels. With the same material, when the fiber cross-sectional area and the areal coverage of a single fiber were constant, the triangular shape had the lowest ultraviolet transmittance and the highest ultraviolet reflectance for a single fiber and also for a fiber bundle. The difference of fiber cross-sectional shapes was also significant in the ultraviolet protection of a single yarn.

Functional application of noble metal nanoparticles in situ synthesized on ramie fibers

Different functions were imparted to ramie fibers through treatment with noble metal nanoparticles including silver and gold nanoparticles. The in situ synthesis of silver and gold nanoparticles was achieved by heating in the presence of ramie fibers in the corresponding solutions of precursors. The unique optical property of synthesized noble metal nanoparticles, i.e., localized surface plasmon resonance, endowed ramie fibers with bright colors. Color strength (K/S) of fibers increased with heating temperature. Silver nanoparticles were obtained in alkaline solution, while acidic condition was conducive to gold nanoparticles. The optical properties of treated ramie fibers were investigated using UV-vis absorption spectroscopy. Scanning electron microscopy (SEM) was employed to observe the morphologies of silver and gold nanoparticles in situ synthesized on fibers. The ramie fibers treated with noble metal nanoparticles showed remarkable catalytic activity for reduction of 4-nitrophenol (4-NP) by sodium borohydride. Moreover, the silver nanoparticle treatment showed significant antibacterial property on ramie fibers.

Rapid and effective cuticle removal from wool fibers using ionic liquid

Wool fibers are composed of cuticle and cortex cells, which are of obvious differences in many properties. The development of methods to isolate the two kinds of cells can provide platform to elucidate the roles they play in the characteristics of wool fibers. Here we demonstrate the cuticle can be completely and rapidly removed from the wool fibers by the use of ionic liquids, with inner cortex intact. Confocal microscope, SEM and FTIR have been applied to study the wool fibers after cuticle removal. In contrast to the traditional/long physical or chemical separation routes (>14 h), our method is very rapid (<1 h). This work demonstrates the ability of ionic liquid as a novel, rapid and efficient media for cuticle/ cortex isolation.

Compositional effects of large graphene oxide sheets on the spinnability and properties of polyurethane composite fibers

Recent advances in wearable electronics, technical textiles, and wearable strain sensing devices have resulted in extensive research on stretchable electrically conductive fibers. Addressing these areas require the development of efficient fiber processing methodologies that do not compromise the mechanical properties of the polymer (typically an elastomer) when nanomaterials are added as conductive fillers. It is highly desirable that the addition of conductive fillers provides not only electrical conductivity, but that these fillers also enhance the stiffness, strength, stretchability, and toughness of the polymer. Here, the compatibility of polyurethane (PU) and graphene oxide (GO) is utilized for the study of the properties of elastomeric conductive fibers prepared by wet-spinning. The GO-reinforced PU fibers demonstrate outstanding mechanical properties with a 200-fold and a threefold enhancement in Young's modulus and toughness, respectively. Postspinning thermal annealing of the fibers results in electrically conductive fibers with a low percolation threshold (≈0.37 wt% GO). An investigation into optimized fiber's electromechanical behavior reveals linear strain sensing abilities up to 70%. Results presented here provide practical insights on how to simultaneously maintain or improve electrical, mechanical, and electromechanical properties in conductive elastomer fibers.

Barrier textiles for protection against microbes

The presence or growth of microbes on textiles may result in a series of problems such as unpleasant odors, cross infection, disease transmission, or discoloration and deterioration of textiles. Imparting textiles with antimicrobial property can effectively eliminate these adversities and thus has been attracting great attention. This chapter summarizes the commonly used antimicrobial agents such as silver, metal oxides, photoactive dyes, quaternary ammonium compounds, N-halamines, triclosan, polybiguanides, chitosan, and plant-derived bioactive agents, their characteristics, toxicity, antimicrobial ability, ecological acceptability, and related textile finishing techniques and evaluation methods. Since durability to repeated washing is the major challenge for the practical use of antimicrobial textiles, the chapter provides details on the technique to immobilize antimicrobial agents onto fibers. In addition, impacts of using antimicrobial textiles on the environment and health are discussed in the last section.

Mechanical behavior of irregular fibers part I : modeling the tensile behavior of linear elastic fibers

Fiber irregularities are inherent to textile fibers, natural fibers in particular. This series of papers examines the impact of fiber irregularity on the mechanical behavior of textile fibers. In the first part, the effect of fiber dimensional irregularities on the tensile behavior of linear elastic fibers is examined, using the finite element method (FEM). Fiber dimensional irregularities are simulated with sine waves of different magnitude and frequency. The results indicate that increasing the level or magnitude of irregularity will decrease the breaking load, breaking elongation and method Young’s modulus of the fiber, while increasing the frequency of irregularity will decrease the breaking load and method Young’s modulus, but the breaking elongation will increase. Fiber dimensional irregularity and the gauge length effect are also simulated in this study.