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Bug-Eating Robots Use Flies for Fuel

Sean Markey
for National Geographic News
March 31, 2006
 
At the Bristol Robotics Laboratory in England, researchers are designing their newest bug-eating robot—Ecobot III.

The device is the latest in a series of small robots to emerge from the lab that are powered by a diet of insects and other biomass.

"We all talk about robots being able to do stuff on their own, being intelligent and autonomous," said lab director Chris Melhuish.

"But the truth of the fact is that without energy, they can't do anything at all."

Most robots today draw that energy from electrical cords, solar panels, or batteries. But in the future some robots will need to operate beyond the reach of power grids, sunlight, or helping human hands.

Melhuish and his colleagues think such release-and-forget robots can satisfy their energy needs the same way wild animals do—by foraging for food.

"Animals are the proof that this is possible," he said.

Bug-munching Bots

Over the last decade, Melhuish's team has produced a string of bots powered by sugar, rotten apples, or dead flies.

The biomass is converted into electricity through a series of stomachlike microbial fuel cells, or MFCs.

Living batteries, MFCs generate power from colonies of bacteria that release electrons as the microorganisms digest plant and animal matter. (Electricity is simply a flow of electrons.)

The lab's first device, named Slugbot, was an artificial predator that hunted for common garden slugs.

While Slugbot never digested its prey, it laid the groundwork for future bots powered by biomass.

In 2004 researchers unveiled Ecobot II. About the size of a dessert plate, the device could operate for 12 days on a diet of eight flies.

"The flies [were] given as a whole insect to each of the fuel cells on board the robot," said Ioannis Ieropoulos, who co-developed Ecobot II as part of his Ph.D. research.

With its capacitors charged, the bot could roll 3 to 6 inches (8 to 16 centimeters) an hour, moving toward light while recording temperature. It sent data via a radio transmitter.

While hardly a speedster, Ecobot II was the first robot powered by biomass that could sense its world, process it, act in it, and communicate, Melhuish says.

The scientist sees analogs in the autonomously powered robots of the future.

"If you really do want robots that are going to … monitor fences, [oceans], pollution levels, or carbon dioxide—all of those things—what you need are very, very cheap little robots," he said.

"Now our robots are quite big. But in 20 to 30 years time, they could be quite minuscule."

(See a photo of small, solar-powered robots.)

More Power

Whether microbial fuel-cell technology can advance enough to power those robots, however, is unclear.

Stuart Wilkinson, a mechanical engineer at the University of South Florida in Tampa, developed the world's first biomass-powered robot, a toy-train-like bot nicknamed Chew-Chew that ran on sugar cubes.

He says the major drawback of MFCs is that it takes a big fuel cell to produce a small amount of power.

Most AA batteries, for example, produce far more power than a single MFC.

"MFCs are capable of running low-power electronics, but are not well suited to power-hungry motors needed for machine motion," Wilkinson said in an email interview.

He added that scientists "need to develop MFC technology further before it can be of much practical use for robot propulsion."

Ieropoulos, Ecobot II's co-developer, agrees that MFCs need a power boost.

He and his colleagues are exploring ways to improve the materials used in MFCs and to maintain resident microbes at their peak.

Bot Weaning

To date, the Bristol team has hand-fed its bots.

But if the researchers are going to realize their vision of autonomously powered robots, then the machines will need to start gathering their own food.

When Ecobot II debuted in 2004, Melhuish suggested one way that it might lure and capture its fly food-source: a combination fly-trap/suction pump baited with pheromones.

Whether the accessory will appear in Ecobot III is anyone's guess. The BRL team remains tight-lipped about their current project, preferring to finish their work in secret before discussing it publicly.

Melhuish will say this, however: "What we've got to do is develop a better digestion system … . There are many, many problems that have to be overcome, and waste removal is one of them."

Will the future bring robot restrooms? Watch this space.

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