Lightweight motor uses carbon nanotubes instead of metal windings
12 June 2025 
Image: Korea Institute of Science and Technology
Korean engineers have built and operated a lightweight electric motor that uses carbon nanotubes (CNTs) instead of traditional copper windings.
Until now, metals such as copper have been the main material used for coils due to their good electrical conductivity, but they have limitations, such as their volatile prices and weight problems resulting from their high densities.
Dr Dae-Yoon Kim and his team at the Korea Institute of Science and Technology (Kist) Composite Materials Research Institute have succeeded in building a motor coil using only CNTs, without any metals.
They used an input voltage to control the motor speed stably, thus demonstrating that the motor was converting electrical energy into a mechanical rotational force, without needing metallic windings. They have reported the results in the journal, Advanced Composites and Hybrid Materials.
CNTs are one-dimensional tube-shaped nanomaterials with carbon atoms arranged in a hexagonal honeycomb structure. They are much lighter than metals, while offering good electrical and thermal conductivity, as well as high mechanical strength.
These properties have long attracted attention to CNTs as a next-generation material, but there have been barriers to real-world industrial applications. One is the residue of catalyst metals used during the manufacturing process that remain as metallic particles on the surface, degrading the CNTs electrical properties. This makes it difficult to use them in high-performance applications.
The Kist team have developed a new CNT purification process using the alignment principle of liquid crystals – a “fourth state” of matter between liquids and solids. The process effectively prevents metallic particles from remaining on the CNT surface.
It can also remove impurities selectively without damaging the nanostructure of the CNTs, making it distinctly different from existing liquid- and gas-phase-based purification methods. The purified CNTs exhibit a much higher conductivity, which has been exploited to produce the electric motors.
“By developing a new concept of high-quality CNT technology that has never existed before, we were able to maximise the electrical performance of CNT coils to drive electric motors without metal,” explains Dr Kim. “Based on the innovation of CNT materials, we will take the lead in localising materials such as conductive materials for batteries, pellicles for semiconductors, and cables for robots.”
The ability to produce motors using lightweight CNT coils could be particularly attractive for transport applications such as electric vehicles, drones or spacecraft. Conventional coils account for a large proportion of the weight of motors in such applications. Reducing their weight not only reduces their energy consumption, but can also increase the range of battery-powered vehicles.
KIST: Facebook
