'Enormous, complicated mounds of soil': A termite mound in Litchfield National Park in the Northern Territory. Photo: Glenn Campbell
The termite, typically reviled as the wood-eating nemesis of buildings and homes, has inspired a new batch of construction robots.
The automated machines, each about the size of a small brick, can work as a team to build any predefined structure given to them, without a leader or step-by-step instructions, as termites are thought to do.
Instead of communicating directly with one another or following a central command, the robots co-ordinate their actions by assessing what work has already been done and adding to it. So, for example, the first robot puts down a block. As it leaves the site, another comes along and senses the block's location. Based on this local information, as well as knowledge about the end product, it decides to put down its own load on top of the first.
Such a process keeps going - ideally with many robots toiling away at once to finish the job faster - until the structure is complete.
This decentralised method of construction is very similar to how the tiny termite is thought to create huge, towering nests.
"[In the US] you hear about termites destroying buildings," said study author and Harvard University computer scientist Justin Werfel. "But in Africa and Australia, they are known for building enormous, complicated mounds of soil."
These oddly shaped towers can be as tall as 12 metres - about the equivalent of a three-story building. And while they may look like big piles of dirt, their simple exterior hides a complex network of ever-evolving tunnels and chambers. Some biologists even believe they provide the colony with airconditioning and atmosphere control.
Dr Werfel and his colleagues wanted to use robotics to harness the power of stigmergy - a process where agents communicate indirectly by sensing and modifying the immediate world around them.
"They're all independent, with each termite doing what it wants to," he said. "It's not like they're getting assigned instructions by the queen; they are just reacting to what they encounter."
Each termite is an organism of fairly low complexity but, using stigmergy, a colony is capable of building a highly complex structure. So the team started with this simple framework: each robot must have its own basic brain and sensors, as well as be programmed with certain "traffic rules" it must obey.
The sensors enable them to see bricks and robots next to them, and the traffic rules depend on the final structure. They prevent robots from placing bricks in places where they might easily collapse, or constructing a scenario where a brick would have to be squashed in between two others.
Each robot, about 20 centimetres long, consists of internal metal gears and hardware as well as 3D printed parts. The bricks themselves are also specially made in a way that helps the robots climb and align them better.
"In our system, each robot doesn't know what others are doing or how many others there are - and it doesn't matter," Dr Werfel said.
The main difference from the real-life insect is that termites don't have a desired end product. Rather, there is a random component involved; given the same starting place, a colony will build a slightly different structure every time. But for constructing a house, for instance, the robots would need to follow a specific blueprint. So Dr Werfel created the option for a user to input a picture of a predefined structure, and the robots will go to town on building it.
He envisions potential applications for his robots to work in places where sending humans would be dangerous and expensive - underwater or on Mars, for instance - or for tedious tasks, such as building levies with sandbags.
Dr Werfel worked on the project with study co-author Kirstin Petersen, a robotics engineer who had independently worked on a collaborative construction project for her master's thesis in Denmark. They teamed up with termite expert Scott Turner, a biologist at the SUNY College of Environmental Science and Forestry.