Sugar and slugs power robot fuel cells

Scientists have developed a bacterial fuel cell that runs entirely on sugar. The cell feeds a robot called Ecobot that follows light around a room and must learn to collect its own energy supply. Ecobot’s design is based on a similar robot ‘trained’ to gather slugs to feed the biodigestor powering its energy system.

Scientists at the Intelligent Autonomous Systems Laboratory (IAS) at the University of West England have built a microbial fuel cell using E.coli bacteria that feed off sugar. As the bacteria break down their food, electrons are produced and captured to power two motors. The motors move the robot towards light sources in burst motions.

Ecobot is being ‘trained’ to balance its stored energy reserve against the requirements of its mission, replenishing its food and draining its waste. The process, known as energetic autonomy, was first tested in another robot, Slugbot, that hunted slugs to feed its off-board digestor unit. The digestor was designed to produce biogas for a methane fuel cell that generated electricity to power a battery pack. When ‘hungry’, Slugbot could download its energy through the batteries.

“We are interested in building robots which will be self-sufficient in terms of decision making and energy – robots which can be left unsupervised to organize their work and nourishment,” says Dr Chris Melhuish of the ISA laboratory. His team are also working on different types of fuels. Microbial fuel cells can be designed to run off garbage such as carrot peelings, says Melhuish.

Slugs were chosen for the first project because they are easy to catch, are a major pest and have no hard shell or skeleton. A robotic system could eventually be used in agricultural fields, with robots hunting the slugs at night when they are most active. Illuminating the field with red light would help the robots find the slugs, as the light would make the vegetation appear darker and the slugs brighter. A nearby fermentation station could power the robots’ batteries from the slugs collected.

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