- NEW YORK -- Scientists have
devised transparent ribbons of carbon nanotubes several yards long that
are highly flexible, yet stronger than the strongest steel sheets.
-
- Nanotechnologists at the University of Texas at Dallas
and their colleagues in Australia have already demonstrated their highly
electrically conductive ribbons could find use in everything from flexible
television screens and solar cells to artificial muscles.
-
- "When we want to try making a device, it's not a
difficult task because we can produce a lot of sheets in a very short period
of time, so we've been able to advance a lot of applications. And everything
is easily scalable," senior researcher Ray Baughman, director of the
University of Texas at Dallas NanoTech Institute, told UPI's Nano World.
- The researchers started with forests of freestanding
multi-walled carbon nanotubes, each roughly 10 nanometers wide and 70 to
300 microns high. They then teased nanotubes away from one side of the
forest with a sticky strip of tape, drawing out the entangled nanotubes
in long sheets. Initially these sheets are very airy and porous, but they
can quickly get compressed into sheets 360 times denser that remain only
50 nanometers thick.
- Scientists have made carbon nanotube sheets before, but
the process could take up to a week or lead to sheets that were not transparent
or as strong. Baughman and his colleagues can produce 2-inch-wide strips
of the airy, porous sheets at up to roughly seven yards per minute, about
a third the production rate for commercial wool spinning.
-
- The researchers have already demonstrated their sheets
can find use as electrodes for bright organic light-emitting diodes in
flat-screen displays. They might also find use in video recorders and solar
power cells. The sheets, which are flexible without losing electrical conductivity,
also make a good starting point for artificial muscles, and Baughman and
his colleagues report experiments in that vein in a paper appearing in
the Aug. 19 issue of the journal Science.
-
- "We hope to go from the very high voltages now used
with artificial muscles, some 4,000 volts, which really is a barrier to
widespread application, to reduce that voltage down with our nanotube sheets
to something more reasonable, like 40 volts," Baughman said.
- The nanotube sheets strongly absorb microwave radiation,
which causes them to heat up. The researchers employed this property to
weld nanotube sheets onto Plexiglas, which affected neither the nanotube
sheets' transparency nor their electrical conductivity.
-
- Baughman suggests windows made with carbon nanotubes
could serve as heating elements and antennas. Other applications the researchers
are exploring include high-strength composites, super-capacitors, batteries,
fuel cells and thermal-energy harvesting cells.
- "Rarely is a processing advance so elegantly simple
that rapid commercialization seems possible, and rarely does such an advance
so quickly enable diverse application demonstrations," Baughman said.
-
- Baughman said his team and their Australian colleagues
are working together with companies and government labs to bring the nanotube
sheets to market. They plan to file five utility patents three months from
now, after which they will begin offering their technology to licensees.
-
- "Ray has done some really pathfinding work here,"
Wade Adams, director of Rice University's Center for Nanoscale Science
and Technology in Houston, told Nano World. He noted his team can also
make forests of freestanding single-walled carbon nanotubes is collaborating
now with Baughman to make similar sheets.
-
- "Nanotechnology has been hyped a lot with many great
expectations of products that will change the world. One example often
given is invisible sunblocker, which does the same job but you can't see
it. But that's cosmetic. It hasn't really changed the world," Ned
Thomas, a materials engineer at the Massachusetts Institute of Technology
in Cambridge, told Nano World.
-
- "With these carbon nanotube sheets, it might not
be too long before you see them in laptop screens and cell phones. Then
you'll have some profits and some companies actually hiring people, and
point to these sheets and not sunblock as the nanotechnology breakthrough
of the year," Thomas added. He said future experiments might consider
coating nanotubes with a variety of chemicals before bundling them into
sheets in order to keep from them sticking or to develop entirely new material
properties.
|
