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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Rumpelstiltskins of the Nanoworld
17 November 2000 7:00 pm
Laboring like modern-day Rumpelstiltskins, scientists have successfully spun submicroscopic carbon nanotubes into nearly pure carbon thread. The precious strands may one day be woven into energy-storing bulletproof vests for Robocop-like soldiers or lightweight cables that tether satellites to Earth.
To make a nanotube, take a hexagonal mesh sheet of carbon atoms and roll it up like a sheet of paper into a tube a few micrometers long and about 1 nanometer wide. Then cap each end with one-half of a buckyball, the spherical 60-atom carbon balls that resemble Buckminster Fuller's geodesic dome. This surprisingly simple cigar-shaped structure is pound for pound the strongest material known. "On a weight basis, a single carbon nanotube is at least 50 times stronger than steel wire," says chemist Philippe Poulin of the Research Center Paul Pascal--CNRS in Pessac, France. When a solution of nanotubes dries out, the tubes stick together and form sheets called "buckypaper." But buckypaper retains only a small fraction of the remarkable strength of the individual tubes. And you can't weave sheets of paper--for that you need thread.
Now, Poulin and his collaborators have found they can spin out silklike strands of carbon by injecting a carefully prepared solution of nanotubes into a rotating solution containing polyvinyl alcohol. If the initial concentration of nanotubes is just right, the stream turns into a mesh ribbon that later collapses into a thread when removed from the spinning bath. Although these fibers don't match individual tubes, Poulin says, they're about three times more difficult to stretch than high-strength nylon fibers.
The fibers should get much stronger as researchers improve the process. "We are not anywhere close to [having] the fibers that will eventually come out," says physicist Richard Smalley of Rice University in Houston, the co-discoverer of buckyballs. "The next year will see a lot of excitement in this field." Already, materials scientist Ray Baughman's group at Honeywell International in Morristown, New Jersey, has spun more durable fibers with a modification of the Poulin group's method; several other teams have also started producing nanotube threads.