Prakash Giri

Graphene fibers (GFs) have emerged as a transformative class of materials that bridge the exceptional intrinsic properties of two-dimensional graphene with scalable macroscopic architectures suitable for practical applications. This review highlights the evolution of graphene fiber development, beginning with a detailed exploration of their diverse morphologies, including cylindrical, porous, belt-type, hollow, helical, elastic, and core–sheath structures, which are intricately linked to their performance across various domains. It further examines a wide range of fabrication techniques such as wet spinning, dry spinning, plasticization spinning, high-speed blow spinning, dry-jet wet spinning, chemical vapor deposition, and dry film scrolling, emphasizing how processing strategies directly influence fiber alignment, stacking density, and defect generation, ultimately determining the mechanical and electrical properties of the fibers. Notably, recent innovations have enabled the production of GFs with tensile strengths exceeding 3 GPa and electrical conductivities surpassing 106 S/m, which has been made possible through improved crystallinity, sheet orientation, and interfacial control. The review also presents cutting-edge applications of graphene fibers, showcasing their versatility in neural recording microelectrodes, regenerative dentistry, wearable textiles, and multifunctional sensors, where their unique combination of high conductivity, flexibility, and biocompatibility offers significant advantages. While substantial progress has been made, critical challenges remain to unlock their true potential, particularly in minimizing structural defects, achieving uniform large-area graphene alignment, and fabricating pristine graphene fibers that are free of any binder. The review concludes with a forward-looking perspective, identifying key research directions and innovations needed to overcome these hurdles and fully realize the role of graphene fibers as next-generation materials in flexible electronics, biomedical systems, and advanced structural applications.

Structural capacitors are multifunctional energy storage systems that can store energy while acting as structural support. This study focuses on the demonstration of a structural capacitor fabricated using a unique combination of carbon nanotubes and fiberglass prepreg that can function at high temperatures without posing significant risk to the structure. Flat structural capacitors made by curing carbon nanotube electrodes inside glass fiber prepreg demonstrated an average capacitance of ~ 0.33–0.371 nF at 20°C. The capacitors remained operational after exposure to a high‐temperature propane torch and demonstrated compliance with the ASTM D6413/D6413M‐22 flammability standard. Scaling up of the size of the capacitors to form structural components of aircraft and automobiles can raise the capacitance value to store a significant amount of energy. The structural capacitor will not only enable the aircraft and automobiles to store energy, but will also shield them from electromagnetic interference, allow them endure high temperatures, and provide a strong yet lightweight structural support. Besides, a capacitor can also provide structural health monitoring in real time. This study evaluates the performance of a high‐temperature capacitor utilizing fiberglass prepreg as both the dielectric and structural material, with carbon nanotube (CNT) sheets as electrodes. While fiberglass prepreg is widely available, the difficulty of scaling up CNT synthesis has been a major limitation in practical applications. This study also aims to overcome this barrier by presenting a feasible approach for producing CNT sheets at an industrially relevant scale, facilitating their integration into multifunctional structural‐electronic components.

This paper showcases current developments in the use of carbon nanotube (CNT) and nanoparticle-based materials for electromagnetic radiation shielding. Electromagnetic radiation involves different types of radiation covering a wide spectrum of frequencies. Due to their good electrical conductivity, small diameter, and light weight, individual CNTs are good candidates for shielding radio and microwaves. CNTs can be organized into macroscale forms by dispersing them in polymers or by wrapping CNT strands into fabrics or yarn. Magnetic nanoparticles can also be incorporated into the CNT fabric to provide excellent shielding of electromagnetic waves. However, for shielding higher-frequency X-ray and gamma ray radiation, the situation is reversed. Carbon’s low atomic number means that CNTs alone are less effective than metals. Thus, different nanoparticles such as tungsten are added to the CNT materials to provide improved shielding of photons. The goal is to achieve a desired combination of light weight, flexibility, safety, and multifunctionality for use in shielding spacecraft, satellites, nuclear reactors, and medical garments and to support lunar colonization. Future research should investigate the effect of the size, shape, and configuration of nanoparticles on radiation shielding. Developing large-scale low-cost methods for the continuous manufacturing of lightweight multifunctional nanoparticle-based materials is also needed.

A carbon nanotube (CNT) sheet is a nonwoven fabric that is being evaluated for use in different textile applications. Several properties of pristine CNT sheets and CNT sheets coated with a polysilazane sealant and coating were measured and compared in the paper. The polysilazane coating is used to reduce the shedding of CNT fibers from the sheet when the sheet is in contact with surfaces. Most fabrics show some shedding of fibers during the washing or abrasion of the fabric. This study showed that the coating reduces the shedding of fibers from CNT fabric. The coating also increased the flame resistance of the fabric. The pristine and coated sheets both have low strength but high strain to failure. The pristine and coated CNT sheet densities are 0.48 g/cc and 0.65 g/cc, respectively. The pristine CNT sheet is approximately 27 μ thick. The coated sheet is approximately 24 μ thick. The coating may have densified the sheet, making it thinner. The thickness of the compliant sheets was difficult to measure and is a source of error in the properties. Characterization results are given in this paper. The results are for comparison purposes and not to establish material properties data. Possible applications for CNT sheets are briefly discussed.

Carbon nanotubes (CNT) sheet is a new type of nonwoven fabric that is being evaluated for different applications. This article presents the first friction-based investigation of the use of CNT sheet as a dust shield. The focus application is for shielding future machinery on the moon from lunar dust. Lunar dust is strongly abrasive; it adheres to all surfaces and causes wear. The absence of an atmosphere and water on the moon, along with its low gravity, and electrostatic adhesion exacerbates the issue of lunar dust, which affects all surfaces, including machinery and human apparel. Friction testing was performed to represent the effect of abrasion occurring on a garment surface while astronauts are working on the moon. The coefficients of static and sliding friction between two CNT sheets, held against each other by a weight, were 0.6 and 0.45, respectively. The presence of lunar regolith simulant reduced the friction coefficients between the two CNT sheets by 33% and 22% for static and sliding friction, respectively. The dust in the sheets was easily cleaned with dry wiping and compressed air, showing no requirement to use water for cleaning in space applications. However, the CNT sheets experienced wear after repeated friction tests. The CNT sheets passed the flammability test standards ASTM D6413/D6413M-15 and NPFA 1971 for applications under extreme heat conditions. Thus, CNT sheet can be considered as a multi-functional material for lunar applications, with shielding protection against dust and electromagnetic waves, and resistance to high temperatures.

Carbon nanotube (CNT) hybrid composites were formed by combining a CNT and silicone elastomer solution with Kevlar yarn, Kevlar fabric, and Kevlar veil materials. The integration of a CNT-silicone matrix with Kevlar yarn and fabric materials produced a composite with moderate electrical and thermal conductivity due to CNT fabric combined with the strength of Kevlar fabric or yarn. In the material synthesis, a notable difficulty was that the CNT-silicone did not bond strongly to the Kevlar. The composites passed the Vertical Flame Test ASTM D6413 and the Forced Air Oven Test NFPA 1971. These hybrid composites can have multiple applications in areas requiring favorable conductivity, strength, and flame and heat resistance. The application areas include firefighter apparel, military equipment, conductive/smart structures, and flexible electronics. The synthesis process used to manufacture CNT-silicone/Kevlar composites yielded composite sheets with an area of 2250 cm². The process is scalable and customizable for the synthesis of CNT composites with tailored properties. Improvements in the bonding of CNT-silicone to Kevlar are being investigated.