spin thread from nanotubes
Technology Research News
If Spiderman wanted an upgrade for the
21st century, he could make his webs from carbon nanotubes.
These microscopic rolled-up sheets of graphite are among the strongest
objects known. They also make good electrical wires. The problem is, nanotubes
are so small -- about 10 carbon atoms in diameter -- that it's difficult
to produce anything made from them.
Researchers looking for ways to make bulk materials from nanotubes have
formed microscopic ropes, pressed sheets and tiny fibers. But these materials
tend to be small, fragile or both.
Researchers from Rensselaer Polytechnic Institute and Tsinghua University
in China have found a way to work on a larger scale, producing thread-like
strands of carbon nanotubes as long as 20 centimeters. The strands could
eventually be used to make very strong fabrics, cables and wires.
To date, scientists have made nanotube fibers using a relatively time-consuming
process that involves combining nanotubes as they are suspended in a liquid,
said Pulickel Ajayan, an associate professor of materials science and
engineering at RPI.
The researchers sidestepped the issue by getting bundles of nanotubes
to line up into strands during the process that produces the individual
nanotubes. "Our approach produces these large strands directly," he said.
The researchers made 10- and 20-centimeter strands that were a third to
half a millimeter in diameter, or around five times the diameter of a
The carbon nanotube strands are as much as 25 times stronger than spider
silk, 15 times stronger than nylon fibers, and one-third the strength
of steel. The strands are still at least 13 times weaker than individual
The strands could be used as electrical cables, strong mechanical devices,
and electrochemical actuators, said Ajayan. Electrochemical actuators
are electrically powered devices, like valves, whose movements are triggered
by chemical reactions.
Nanotubes, a natural component of soot, are commonly made in high concentrations
by condensing a hot chemical vapor that includes carbon atoms. The researchers
got their nanotubes to form in strands by producing them at very high
temperatures and by injecting the carbon vapor into a gently flowing stream
of hydrogen gas. The nanotube strands grew in the direction of the flow.
The research is a significant advance, said Philippe Poulin, a materials
scientist at Paul Pascal Research Center, a national laboratory in France.
"This work is very nice, and fascinating," he said. Poulin's research
team has also developed a process for making nanotube fibers.
"The strands they have obtained by direct synthesis are the longest and
strongest assemblies made only of carbon nanotubes," said Poulin. "The
nanotube strands [have] better physical properties than [our] fibers,"
The nanotube materials developed by the two teams are different and are
likely to have different applications, Poulin added.
The nanotube strands could be used in practical applications in two to
five years, said Ajayan. "More optimization is necessary to improve [their]
mechanical properties," he said.
Ajayan's research colleagues were Hongwei Zhu, Cailu Xu and Dehai Wu of
Tsinghua University in China, and Bingqing Wei and Robert Vajtai of Rensselaer
Polytechnic Institute. They published the research in the May 3, 2002
issue of the journal Science. The research was funded by the National
Science Foundation (NSF) and the Ministry of Science and Technology in
Timeline: 2-5 years
TRN Categories: Materials Science and Engineering; Nanotechnology
Story Type: News
Related Elements: Technical paper, "Direct Synthesis of
Long Single-Walled Carbon Nanotube Strands," Science, May 3, 2002
12/19, 2002, 2002
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