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C-nanotubes textiles with high electrical conductivity

29 Apr '17

3 min read

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesised thin carbon nanotube textiles that exhibit both high electrical conductivity and toughness which is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including biological and structural health monitoring sensors," explained Sameh Tawfick, an assistant professor of mechanical science and engineering at Illinois.

"Aligned carbon nanotube sheets are suitable for a wide range of application spanning the micro- to the macro-scales including Micro-Electro-Mechanical Systems (MEMS), supercapacitor electrodes, electrical cables, artificial muscles, and multi-functional composites," Tawfick said.

Carbon nanotubes, which have been around since the early nineties, have been hailed as a "wonder material" for numerous nanotechnology applications. These tiny cylindrical structures made from wrapped graphene sheets have diameter of a few nanometres - about 1,000 times thinner than a human hair, yet, a single carbon nanotube is stronger than steel and carbon fibres, more conductive than copper, and lighter than aluminum.

However, it has proven really difficult to construct materials, such as fabrics or films that demonstrate these properties on centimetre or metre scales. The challenge stems from the difficulty of assembling and weaving carbon nanotubes (CNTs) since they are very small, and their geometry is very hard to control.

"The study of the fracture energy of CNT textiles led us to design these extremely tough films," stated Yue Liang, a former graduate student with the Kinetic Materials Research group and lead author of the study which appears in Advanced Engineering Materials.

Beginning with catalyst deposited on a silicon oxide substrate, vertically aligned carbon nanotubes were synthesised via chemical vapour deposition in the form of parallel lines of 5?micrometre width, 10?micrometre length, and 20-60?micrometre heights.

"The staggered catalyst pattern is inspired by the brick and mortar design motif commonly seen in tough natural materials such as bone, nacre, the glass sea sponge, and bamboo. Looking for ways to staple the CNTs together, we were inspired by the splicing process developed by ancient Egyptians 5,000 years ago to make linen textiles. We tried several mechanical approaches including micro-rolling and simple mechanical compression to simultaneously re-orient the nanotubes, then, finally, we used the self-driven capillary forces to staple the CNTs together," Liang added.

"This work combines careful synthesis, and delicate experimentation and modeling. This new CNT textile, with simple flexible encapsulation in an elastomer matrix, can be used in smart textiles, smart skins, and a variety of flexible electronics. Owing to their extremely high toughness, they represent an attractive material, which can replace thin metal films to enhance device reliability," Tawfick said. (SV)

Fibre2Fashion News Desk – India