Peking University, July 11, 2012: Peking University (PKU) Nano Scientist Cao Anyuan and his co-workers have fabricated springy carbon nanotube ropes which are super stretchable. These ropes are made by twist-spinning single-walled nanotube films to form closely arranged loops with long-distance order. The nanotube ropes have spring constants comparable to conventional steel and can sustain very large tensile strains (up to 285%) without structural failure by loop separation and straightening.
Professor Cao heads the Lab for Nano Devices and Applications in the Department of Materials Science and Engineering, College of Engineering at PKU. His co-workers in this research include professors and students from the Center for Composite Materials and Structures, Harbin Institute of Technology, the Key Laboratory for Advanced Materials Processing Technology and Department of Mechanical Engineering, Tsinghua University.
Their article “Super-Stretchable Spring-Like Carbon Nanotube Ropes” and its cover, published on June 5 on Advanced Materials , appeared both in the top 10 for the Journal’s last week's most downloaded papers.
“I don't think we've had a paper and its cover appear in the same top 10 list before.” said Dr. David Flanagan, Editor-in-Chief of the Journal.
Cover of the article "Super-Stretchable Spring-Like Carbon Nanotube Ropes" on Advanced Materials, June 5, 2012
Macroscopic, multifunctional carbon nanotube (CNT) yarns made by solution extrusion or twist spinning processes have stimulated tremendous interest recently. Attractive properties of CNT yarns include unlimited yarn length, high strength-to-weight ratio, high flexibility and electrical conductivity that are superior to conventional fibers and rubber-like materials. Spun CNT-based materials (yarns, sheets, biscrolled yarns) already demonstrated potential applications as light-emission source, torsional actuators, electrochemical catalytic media and carriers for functional particles.
However, one intrinsic limitation of these yarns is their low tensile strains and stretchability; pure or composite yarns generally sustain strains of less than 10% before fracture in tension, and reduced strains after polymer reinforcement or solvent densification in some examples. According to previous studies, if one could impart high stretchability on these yarns while maintaining their high strength and conductivity, many more interesting applications would be possible as stretchable conductors/electrodes and nanoelectronic devices such as integrated circuits, strain sensors, supercapacitors and photovoltaics.
Illustration of the spinning process
The team reports a yarn-derived spring-like CNT rope, which consists of uniform, neat loops with perfect arrangement over long distance. These CNT ropes can produce significant elongations and sustain tensile strains of up to 285% by loop opening and straightening during elongation, resulting in high toughness for fracture. Within a moderate strain (20%), the CNT rope behaves like a spring with a stable spring constant when stretched by 1000 times with energy absorption during contraction. No degradation was observed in the rope conductivity after repeated strain cycles. The stretchability coming from the spring structure is 20 times higher than pure CNT yarns in straight form while maintaining good strength and conductivity.
“The highly-stretchable, tough and conductive carbon nanotube ropes may find applications in many areas such as stretchable conductors and electrodes, strain sensors, and energy dissipation fibers”, said Cao, “In the future, these nanostructure-based ropes could be further reinforced by densification or polymer infiltration”.
The research work was financially supported by the National Natural Science Foundation of China (NSFC, Grant No. 2011-11002042) and NSFC 51072005.
Paper cited:
Edited by: Arthars
Source: College of Engineering
