Source:
http://www.newscientist.com/article.ns?id=dn8859&feedId=online-news_rss20
Methanol-powered artificial muscles start to flex
19:00 16 March 2006
NewScientist.com news service
Zeeya Merali
Methanol-powered artificial muscles have been created
by researchers
aiming to create battery-free robotic limbs and
prosthetics.
"One day you could find yourself sitting in a bar next
to a humanoid
robot, who is taking a shot of vodka to give himself
the energy to go
to
work," jokes Ray Baughman, a nanotechnologist at the
University of
Texas
at Dallas, US.
"The most athletic robots around today are chained to
a power source,
so
they can't move about freely," he explains. In an
effort to remove the
robots from their battery-shackles, Baughman and
colleagues have
designed
two types of artificial muscle that also act as fuel
cells â
converting
chemical energy to mechanical movement.
The first type of muscle is made from a
nickel-titanium shape-memory
wire
coated in a platinum catalyst. When fumes of methanol,
hydrogen and
oxygen
pass over the platinum coating, they react, releasing
heat that warms
the
wire, making it contract. When the flow of fuel is
stopped, the wire
expands and returns to its original length. The wire
muscle can
generate
100 times the force of a natural muscle of the same
size, says
Baughman.
Energy saver
The team's second artificial muscle is made from
sheets of carbon
nanotubes, coated in a catalyst. It is not yet as
powerful as the wire
muscle, but could potentially overtake it, he says.
As the fuel reacts with oxygen above the surface of
the nanotube sheet,
it
releases a charge that make the sheet expand. The big
advantage of the
nanotube muscle is that it can also act as a
capacitor, storing up
electric energy it does not immediately need for later
use, Baughman
explains.
The team are now working out exactly how to control
the flow of fuel in
practical prosthetic applications. Baughman believes
that people with
limited finger or arm mobility could control an
artificial muscle using
very slight movements to open and shut a valve to
release the fuel. A
second challenge for the group is ensuring that the
muscles do not
overheat as they contract, adds Baughman.
âIt is very clever that the muscle itself is the
fuel cell,â says
Siegmar
Roth, an artificial muscle expert at the Max Planck
Institute in
Stuttgart, Germany. âThis will be very good for
medical applications
because you canât put high voltages into humans, but
these work on
low
voltages.â
Reference: Science (vol 311, p 1580)
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