We have been focusing on carbon nanotubes (CNTs) as a material for next-generation electric wires that are lighter and more conductive than copper and aluminum wires. CNT single fiber has a greater conductivity than copper and the highest tensile strength of any known material. Aiming at the practical application of CNT electric wires, we have discovered the effectiveness of applying tensile stress to CNTs during the growing process from iron catalysts. In addition, at the University of Tsukuba, where a joint research was conducted, the growth of centimeter-class single fibers was observed in high-speed airflow, suggesting that stress applied during the growth contributes to the lengthening of CNTs. Using this principle as a basis for the growth method, we have created a metric-class CNT yarn that aggregates these long CNT single fibers. The new yarn has several times the strength of the conventional CNT yarn and exceeds the tensile strength of commercially available carbon fibers. This yarn will not only replace carbon fibers but also create new applications that have never been seen before.
