|Continuous carbon nanotubes (CNTs) yarn is yet not available commercially. The Tianjin University from China has conducted research and successfully produced a kilometer long carbon nanotube fiber with excellent uniformity. Its internal structure makes it versatile for use in a wide range of applications. The ability to fabricate continuous, multifunctional yarns represents an important step makes it possible for materials engineers to exploit the outstanding mechanical properties of CNTs for applications in fibers, composites, fabrics and other larger-scale structures and devices.
So far, researchers have been working on several processes to make macro scale CNT fibers. Development of a continuous and weavable pure carbon nanotube yarn remains a major challenge in the fabrications as CNT yarns so far obtained from the different processes are monolithic in structure. The team has been able to demonstrate the fabrication of a novel continuous yarn of CNTs with a multiple-layer structure by the chemical vapor deposition (CVD) spinning process. The yarn consists of multiple monolayers of CNTs concentrically assembled in seamless tubules along the yarn axis. Fabrication of a CNT yarn by the CVD spinning process relies on the assembly of CNTs in the gas flow by van der Waals interactions. The CNTs assemble in the gas flow when produced in a sufficiently high yield with a high purity such that interaction occurs. Their assembly is, therefore, greatly dependent on the chemistry of the carbon sources. The assembly of CNTs in the gas flow forms a continuous sock-like CNT integrate, which can be mechanically spun out into a CNT yarn. Spinning of multilayered CNT yarns is based on the team's discovery that CNTs can self-assemble into a multilayered CNT 'sock' in the gas flow when a mixture of acetone and ethanol is used as the carbon source. The core scientific discovery is that carbon nanotubes can self assemble in the gas flow, into multiple geometry of layered structures by controlling the reaction chemistry and synthesis conditions.
This novel technique makes it possible to fabricate CNT yarns and multiple functional yarns that can be spun over kilometers with controlled CNT structures at atomic levels and micro levels. This is made possible through the innovative spinning methodology including the development of densification method and control of spinning.
The development of a continuous, wearable multilayered CNT yarn which opens the way for a wide range of structural and functional applications, including composites, intelligent fabrics, catalyst supports, and sensors. The yarns can be applied in composites, fabric, structural and functional components just like conventional fibers but with multifunctional properties such as high electrical conductivity and superior mechanical properties. These carbon nanotube yarns can be made either dense or hollow or multiple layered structures to meet specific structural and functional applications. The hollow and multiple layer structures allows mass transfer with enhanced contact which can be applied in many fields such as electrochemical system for the development of energy storage materials and in bio-system as tissues, vascular and nerves. The team is working towards enlarging the production to provide quantity CNT yarns; fabricating woven fabrics; using the yarn to make composites; and exploring its potential in electrochemical systems and biomaterials including sensors and tissue materials.