Self-organising termite-inspired robots have constructed towers, castles and pyramids without any supervision or detailed instructions.
The Termes bots possess the same social intelligence as a colony of termites, which means that they can simply be given an overall concept of the finished job and left to get on with it, researchers said.
All that guides the six-inch-long robots are signals from infrared and ultrasound sensors and simple "traffic" rules that determine whether to go or stop, but this allows them to know when to lift a building brick and where to attach it, how to avoid collisions, and even how to reach higher levels by constructing staircases.
Their creators hope that, in future, similar autonomous machines could be used to build full scale structures for human use, possibly things such as earthquake shelters, underwater habitats, or bases on the moon or Mars where it might be dangerous or difficult for humans to work.
"The key inspiration we took from termites is the idea that you can do something really complicated as a group, without a supervisor, and secondly that you can do it without everybody discussing explicitly what's going on, but just by modifying the environment," said US computer scientist Professor Radhika Nagpal, from Harvard University.
Scientists turned to the termites for inspiration due to their impressive feats of cooperation, by which millions of the insects work together to create mounds that can stand eight foot tall and act as sophisticated air conditioning systems for nests.
Each mound contains a complex system of tunnels and shafts but unlike human builders, termites need no detailed blueprints from which to work, instead relying on a process called "stigmergy" – a kind of implicit communication by which they observe each other interacting with the environment and act accordingly in a way that, scaled up, looks intelligent.
The Termes bots employ the same principle, which means that unlike other working robots, such as those in car factories, they require no centralised controller or complex system of talking to each other.
Each robot has a set of wheels and a single lifting arm with a spring-loaded gripper and the bots use infrared sensors to detect black and white patterns on the bricks, and sonar for navigation.
Just two kinds of rules governs the building project. One determines how a robot makes its next move and applies to any structure being built and the other consists of "traffic laws" that correspond to a specific structure.
The traffic laws tell robots at any site which sites they are allowed to go to next, and maintain a constant flow of robots and material through the structure.
"If they built carelessly, it would be easy for them to build in a way where they got stuck," said team member Dr Justin Werfel, from the Wyss Institute for Biologically Inspired Engineering in Cambridge, USA.
"The safety checks involve a robot looking at the sites immediately around itself, paying attention to where the bricks already are and where others are supposed to be, and making sure certain conditions in that local area are satisfied."
One of the key advantages of the system is that it is not dependent on a set number of interactive units working together, Werfel explained.
"Individual robots can break down but the rest can carry on," he said. "There's no one critical element that brings everything down if one fails."
During the study, the scientists filmed the robots recovering from unexpected changes made to the structures they were building.
"When many agents get together, whether they're termites, bees or robots, often some interesting, higher-level behaviour emerges that you wouldn't predict from looking at the components themselves," Werfel said.
"Broadly speaking, we're interested in connecting what happens at the low level, with individual agent rules, to these emergent outcomes."
A paper on the Termes robots is published in the latest edition of the journal Science. The researchers are also talking about their work at the American Association for the Advancement of Science's annual meeting in Chicago.
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