Carbon nanotubes (CNTs) have ultrahigh strength, high electrical conductivities, high thermal conductivities, electric field emissions, gas sensitivities, and other functional properties. These outstanding mechanical, physical, and multifunctional properties of CNTs, in combination with their unique 1D nanostructures with high specific areas, allow for a wide range of potential applications such as structural fibers, composites, multifunctional fabrics, and devices. The fabrication of CNTs into a continuous multifunctional CNT yarn is an important step towards these macroscopic applications. Several processes are under development to fabricate macroscopic CNT fibers, including wet spinning of CNTs from polymer dispersions or acid dispersions, dry spinning from aligned CNT matrices, and direct spinning from chemical vapor deposition (CVD) reactions. While the development of a continuous and weavable pure CNT yarn remains a major challenge in the fabrications, CNT yarns so far obtained from the different processes are monolithic in structure, although a hollow yarn was demonstrated from a wet drawing process. One the other hand, CNTsheets or films have been fabricated by drying CNT dispersions, drawing or infiltrating of CNT arrays, and by CVD spinning. These 2D CNT assemblies have demonstrated applications as catalyst supports, molecular sieves, infiltrators, conductors, electromagnetic shields, capacitors, and artificial tissues. If CNTs can be made into continuous yarns with a layered structure, they will combine the weavable property of fibers and the structural characteristic of films and can be adopted for numerous applications.

In the present work, we report the fabrication of a novel continuous yarn of CNTs with a multiple-layer structure by the CVD spinning process. The yarn consists of multiple monolayers of CNTs concentrically assembled in seamless tubules along the yarn axis. The development of a water-densification and spinning process allows us to spin the CNT yarn continuously with a yarn length of over several kilometers and a yarn quality close to conventional textile yarns. The CNTyarn can be controlled to be either hollow or monolithic with compacted or detached CNT monolayers by controlling the spinning process. This layered multifunctional CNT yarns combine superior mechanical properties, electrical conductivities, and surface structures, and have potential applications as structural fibers, composites, woven fabrics, catalyst supports, energy storage materials, artificial tissue, and so on.

        The development of a continuous, weavable multilayered CNT yarn with superior mechanical, structural, surface, and electrical properties opens the way for a wide range of structural and functional applications, including composites, intelligent fabrics, catalyst supports, and sensors. The layered yarn with a micrometer-sized hollow and a nanometer-sized porous electrically conductive wall is attractive for the development of novel biomaterials, including vascular, neural, and controlled drug- release materials. Finally, the successful fabrication of the textile yarn of CNT could stimulate the development of other types of layered fibers on an industrial scale.