July 25, 2015

In the race to produce highly stretchable conductors, researchers have developed a new technique that aligns sheets of layered carbon nanotubes along stretched rubber cores, creating an extremely flexible conductive fiber.

From pacemaker leads to flexible displays and batteries, there is a growing need for fibers that don't lose their conductivity upon repeated stretching, twisting or flexing. The challenge has been to create a conductive material that is highly elastic, but that maintains a high level of conductivity when distorted - which is often not the case for existing materials that use variations of nanofibers, graphene, fiber and rubber. Liu and colleagues dramatically improve upon these other materials by stretching rubber fiber cores to roughly 1400%, and then aligning a sheath of carbon nanotubes in parallel to the strained core. Upon relaxation of the core, the nanotube sheath will buckle but will not break. This technique offers an impressive stretch-to-conductivity ratio, where there is less than a 5% decrease in electrical conductivity when the material is stretched by 1000%. The team has already taken this technique one step further by creating a more complicated combination of materials that uses a second layer of rubber. This allows for a high degree of twist within the combined materials, which could be used to control movement in artificial muscles. By creating significantly more efficient materials, this research could have a substantial impact on future medical devices, optical elements, and robotics. A Perspective by Tushar Ghosh provides more insights about this new technique.