Hungry Robots!
Duncan Graham-Rowe
From New
Scientist magazine, 22 July 2000.
Could the future of robotics be
a toy train with a taste for flesh?
BEWARE: a hungry, flesh-eating robot
called Chew Chew could have designs on you. Not that you
won't hear the beast coming: Chew Chew is a 12-wheeled
monster that looks more like a train. But he's also the
first robot to be completely powered by food. He's
called a gastrobot--and he is set to make his public
debut in August, at a robotics conference in Hawaii.
Chew
Chew's "stomach" is a microbial fuel cell (MFC),
a device that enslaves a population of bacteria, in this
case E. coli, to break down food and convert chemical
energy into electricity. The ideal fuel, in terms of
energy gain, is meat, says inventor Stuart Wilkinson of
the University of South Florida in Tampa.
"Vegetation is not nearly as nutritious," he
explains. But eating meat requires you to catch it first
and that, in turn, requires a lot of extra energy and
complex behaviours, he says.
Early applications for gastrobots are
likely to include mowing lawns--and grazing on grass
clippings for fuel. The long-term idea is to develop
autonomous robots that can feed themselves, says
Wilkinson.
The robot consists of three wheeled
wagons, each about a metre long. For convenience, says
Wilkinson, Chew Chew only eats sugar cubes at the moment
because these are almost entirely broken down by the
microbes, producing virtually no waste.
The microbes produce enzymes that
break down carbohydrates. "Every time you break a
large molecule like glucose into smaller molecules you
release electrons," he says. These electrons are
harnessed to charge a battery by a reduction and
oxidation (redox) reaction. Wilkinson says this is
analogous to blood supply and respiration in a
mammal--but delivering electrons instead of oxygen.
Although Chew Chew doesn't produce
much in the way of waste--just carbon dioxide and
water--it would produce more if it ate vegetation or
meat, says Wilkinson.
"At the moment," says
Wilkinson, "we have to feed it like a baby because
it doesn't have any arms or legs." In fact, as
robots go, Chew Chew is a bit of an underachiever. The
MFC does not produce enough power to move it, so instead
the electricity is used to charge its batteries. Only
when the batteries are fully charged does the robot have
enough power to move forward. When the batteries are
drained, the cycle repeats itself.
"Turning food into electricity
isn't unique," he says. "What I've done is
make it small enough to fit into a robot."
Wilkinson says the gastrobot also
differs from other projects, such as the slug-eating
robot being developed at the University of the West of
England in Bristol, because it does its digestion
on-board. This makes a lot more sense in terms of energy
efficiency than shuttling back and forth between your
quarry and the MFC.
Chris Melhuish of the slugbot team
says that the potential is there to use this sort of
technology for vehicles, but it's a long way off.
"The energy demands would be huge to run a train or
even a small car," he says. Perhaps it would be
more practical to build an underwater robot. "If a
robot fish could be built then it would make more sense
to build a robot which ate fish and monitored beaches
for sharks." But Wilkinson doesn't think it's good
to give gastrobots a taste for meat. "Otherwise
they'll notice there's an awful lot of humans running
around and try to eat them," he warns.
© Copyright New
Scientist, RBI Limited 2000
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