Termites can build huge, elaborate mounds that rise up from the ground like insect skyscrapers; scientists have now created little robots that act like termites to build a made-to-order structure.

"Termites are the real masters of construction in the insect world," says Justin Werfel of the Wyss Institute for Biologically Inspired Engineering at Harvard University. "The largest termite mound on record was 42 feet tall."

Termites by the millions work together to build their intricate, large-scale structures — doing stuff like pushing bits of mud around. And yet they're not following a blueprint or listening to orders from some termite foreman. Instead, they seem to sense what's around them and apply some simple rules to decide what to do next.

Werfel and his colleagues, Kirstin Petersen and Radhika Nagpal, wanted to see if robots could build in the same way.

"We've created this system of multiple independent robots that build things we ask for," says Werfel, "and they do it more like the way insects act than the way that robots normally act."

The robots don't look like termites. Instead, they look more like black, mechanical beetles, about 8 inches long. They have just a few on-board sensors that let them navigate around a work site set up in a lab.

Each robot can grab a specially-designed square brick, carry it on its back, and then set it down. In the journal Science, the researchers show how programming the robots to follow different sets of rules can produce a variety of structures, from castles to pyramids.

"They build things that are much larger than themselves," says Werfel. "They climb on what they are ... building to get to higher places, and they coordinate what they are doing using a tool that termites use.

"Rather than talk to one another directly, they coordinate indirectly by changing their shared environment," he explains. "So one puts down some material, another one comes along and reacts to that material, and uses that to help it decide later whether to put more material down."

So far, the robots have only made modest structures — and they do it slowly. For example, they built one that's shaped like a trident, says Werfel. "That involves only eight bricks, and that takes half an hour."

The vision is that, someday, swarms of robots could stack up sandbags to protect against flooding, or go to Mars and build living quarters for astronauts. That's still a long way off. But this is a proof of principle study that construction robots can work together like termites, says Hod Lipson, an engineer at Cornell University who specializes in robotics.

"The idea has been around for a while, that you can have robots cooperate to construct something larger than themselves," Lipson says. "But no one has really been able to get that to work." This study, he says, opens up lot of new possibilities for thinking about how to use machines as builders in the future.

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