Researchers at The University of Texas at Dallas (UT Dallas), USA, have announced a new technology for producing weavable, knittable, sewable and knottable yarns containing otherwise unspinnable powders.
A tiny amount of host carbon nanotube web holds guest powders in the corridors of highly conducting scrolls, without altering their performance for high-tech applications such as energy storage, energy conversion and energy harvesting, explained Nanotechnologists at the university.
With conventional technology, powders are either held together in a yarn using a polymer binder or incorporated on fibre surfaces. Both approaches can restrict powder concentration, powder accessibility for providing yarn functionality, or the strength needed for yarn processing into textiles and subsequent applications.
In a recent issue of the journal Science, co-authors working in the Alan G. MacDiarmid NanoTech Institute of UT Dallas describe the use of “bi-scrolling” to solve these problems.
“In this study, we demonstrated the feasibility of using our bi-scrolled yarns for applications ranging from superconducting cables to electronic textiles, batteries and fuel cells,” said Dr. Ray H. Baughman, Robert A. Welch Professor of Chemistry and director of the UT Dallas NanoTech Institute.
Bi-scrolled yarns get their name from the way they are produced: A uniform layer of guest powder is placed on the surface of a carbon nanotube web. This two-layer stack is then twisted into a yarn.
The carbon nanotube webs used for bi-scrolling are not ordinary, they can be lighter than air and stronger pound-per-pound than steel. Four ounces of these webs would cover an acre of land and are about a thousand times thinner than a human hair.
These strong carbon nanotube webs hold together yarns that are mostly powders and can even be machine-washed. The web’s thinness means that hundreds of scroll layers can be included in a bi-scrolled yarn no thicker than a human hair.
The choice of imbedded powder determines yarn function. For instance:
- UT Dallas researchers used yarns imbedded with metal oxide powder to make high-performance lithium ion batteries that can be sewn into fabrics.
- Bi-scrolled yarns for self-cleaning fabrics were obtained using photocatalytic powder.
- A powder of nitrogen-containing carbon nanotubes provided highly catalytic yarns for chemical generation of electricity, avoiding the need for expensive platinum catalyst.
- Using other types of powders, the team made superconducting yarns for potential use in applications ranging from powerful magnets to underground electrical transmission lines.
“UT Dallas’s bi-scrolling technology is rich in application possibilities that go far beyond those we described in Science,” Baughman said. “For instance, our collaborator, professor Seon Jeong Kim of Hanyang University in Korea has already used bi-scrolled yarn to make improved biofuel cells that might eventually be used to power medical implants.”