BEWARE: a hungry, flesh-eating robot called Chew Chew could have designs on
you. Not that you won鈥檛 hear the beast coming: Chew Chew is a 12-wheeled monster
that looks more like a train. But he鈥檚 also the first robot to be completely
powered by food. He鈥檚 called a gastrobot鈥攁nd he is set to make his public
debut in August, at a robotics conference in Hawaii.
Chew Chew鈥檚 鈥渟tomach鈥� 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. 鈥淰egetation is not nearly as nutritious,鈥� 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鈥攁nd grazing on grass clippings for fuel. The long-term idea is to
develop autonomous robots that can feed themselves, says Wilkinson.
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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. 鈥淓very time you
break a large molecule like glucose into smaller molecules you release
electrons,鈥� 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鈥攂ut delivering electrons instead
of oxygen.
Although Chew Chew doesn鈥檛 produce much in the way of waste鈥攋ust carbon
dioxide and water鈥攊t would produce more if it ate vegetation or meat, says
Wilkinson.
鈥淎t the moment,鈥� says Wilkinson, 鈥渨e have to feed it like a baby because it
doesn鈥檛 have any arms or legs.鈥� 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.
鈥淭urning food into electricity isn鈥檛 unique,鈥� he says. 鈥淲hat I鈥檝e done is
make it small enough to fit into a robot.鈥�
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鈥檚 a long way off. 鈥淭he energy
demands would be huge to run a train or even a small car,鈥� he says. Perhaps it
would be more practical to build an underwater robot. 鈥淚f a robot fish could be
built then it would make more sense to build a robot which ate fish and
monitored beaches for sharks.鈥� But Wilkinson doesn鈥檛 think it鈥檚 good to give
gastrobots a taste for meat. 鈥淥therwise they鈥檒l notice there鈥檚 an awful lot of
humans running around and try to eat them,鈥� he warns.