Triaxial Carbon Nanotube/Conducting Polymer Wet-Spun Fibers Supercapacitors for Wearable Electronics

The ubiquity of wearables, coupled with the increasing demand for power, presents a unique opportunity for nanostructured fiber-based mobile energy storage systems. When designing wearable electronic textiles, there is a need for mechanically flexible, low-cost and light-weight components. To meet this demand, we have developed an all-in-one fiber supercapacitor with a total thickness of less than 100 μm using a novel facile coaxial wet-spinning approach followed by a fiber wrapping step. The formed triaxial fiber nanostructure consisted of an inner poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) core coated with an ionically conducting chitosan sheath, subsequently wrapped with a carbon nanotube (CNT) fiber. The resulting supercapacitor is highly flexible, delivers a maximum energy density 5.83 Wh kg-1 and an extremely high power of 1399 W kg-1 along with remarkable cyclic stability and specific capacitance. This asymmetric all-in-one fiber supercapacitor may pave the way to a future generation of wearable energy storage devices.

Electrically Conducting Hydrogel Graphene Nanocomposite Biofibers for Biomedical Applications

Conductive biomaterials have recently gained much attention, specifically owing to their application for electrical stimulation of electrically excitable cells. Herein, flexible, electrically conducting, robust fibers composed of both an alginate biopolymer and graphene components have been produced using a wet-spinning process. These nanocomposite fibers showed better mechanical, electrical, and electrochemical properties than did single fibers that were made solely from alginate. Furthermore, with the aim of evaluating the response of biological entities to these novel nanocomposite biofibers, in vitro studies were carried out using C2C12 myoblast cell lines. The obtained results from in vitro studies indicated that the developed electrically conducting biofibers are biocompatible to living cells. The developed hybrid conductive biofibers are likely to find applications as 3D scaffolding materials for tissue engineering applications.

Three-Dimensional Hierarchically Porous Graphene Fiber-Shaped Supercapacitors with High Specific Capacitance and Rate Capability

Chemically converted graphene fiber-shaped supercapacitors (FSSCs) are highly promising flexible energy storage devices for wearable electronics. However, the ultralow specific capacitance and poor rate performance severely hamper their practical applications. They are caused by severe stacking of graphene nanosheets and tortuous ion diffusion path in graphene-based electrodes; thus, the ultralow utilization of graphene has been rarely carefully considered to date. Here, we address these issues by developing three-dimensional hierarchically porous graphene fiber with the incorporation of holey graphene for efficient utilization of graphene to achieve fast charge diffusion and good charge storage capability. Without deterioration in electrical but robust mechanical properties, the optimal graphene fiber shows ultrahigh specific capacitance of 220.1 F cm^-3 at current density of 0.1 A cm^-3 and boosted specific capacitance of 254.3 F cm^-3 at 0.1 A cm^-3 after nitrogen doping. Moreover, the nitrogen-doped 40% holey graphene hybrid fiber-assembled FSSC exhibits ultrahigh rate capability (96, 91, and 87% at current density of 0.5, 1.0, and 2.0 A cm^-3, respectively, and 67% even at ultrahigh current density of 10.0 A cm^-3) and excellent cycle stability (95.65% capacitance retention after 10 000 cycles). The contribution of three-dimensional interconnected hierarchically porous network to the enhanced electrochemical (EC) performance is semiquantitatively elucidated by Brunauer-Emmett-Teller and energy dispersive spectroscopy mapping. Our work gives insights into the importance of fully utilizing graphene and provides an efficient strategy for high EC performance in chemically converted graphene-based FSSCs.

Hybrid carbon nanostructured fibers: stepping stone for intelligent textile-based electronics

The journey of smart textile-based wearable technologies first started with the attachment of sensors to fabrics, followed by embedding sensors in apparels. Presently, garments themselves can be transformed into sensors, which demonstrates the tremendous growth in the field of smart textiles. Wearable applications demand flexible materials that can withstand deformation for their practical use on par with conventional textiles. To address this, we explore the potential reasons for the enhanced performance of wearable devices realized from the fabrication of carbon nanostructured fibers with the use of graphene, carbon nanotubes and other two-dimensional materials. This review presents a brief introduction on the fabrication strategies to form carbon-based fibers and the relationship between their properties and characteristics of the resulting materials. The likely mechanisms of fiber-based electronic and storage devices, focusing mainly on transistors, nano-generators, solar cells, supercapacitors, batteries, sensors and therapeutic devices are also presented. Finally, the future perspectives of this research field of flexible and wearable electronics are discussed. The present study supplements novel ideas not only for beginners aiming to work in this booming area, but also for researchers actively engaged in the field of fiber-based electronics, dealing with advanced electronics and wide range of functionalities integrated into textile fibers.

Fabrication of a graphene coated nonwoven textile for industrial applications

A hybrid electrically conductive polyester–graphene textile was fabricated as a high-performance smart textile for geotextile and/or heating element applications.