Insect-inspired drones work together to 3-D print structures

In the future, such machines might do construction or repairs in hard-to-reach places

Two identical drones worked together to build a cake-sized cylinder. When one drone went to reload, the other hovered over the structure, squirting out ribbons of a cement-like material.

Imperial College London, University College London, University of Bath

Drones already fly and spy. Now, they can build too. For the first time, free-flying robots have 3-D printed structures. A pair of drones working together made a tower taller than a person. Engineers demonstrated this new method of 3-D printing in the lab. They shared their success in Nature on September 22.

Mirko Kovac, who co-led the research, says that animal builders inspired him. “Wasps are amazing,” he says. “Bees are incredible.” These insects work together in swarms to make nests much larger than themselves.

Kovac is a roboticist at Imperial College London in England. He also works at Swiss Federal Laboratories for Materials Science and Technology (Empa) in Dübendorf. His co-leader on this project was architect Robert Stuart-Smith of the University of Pennsylvania in Philadelphia and University College London in England.

a wasp nest
Wasps work together to build large nests. They do it without a blueprint. Each insect “sees what is already built and works on top of that,” says roboticist Mirko Kovac. RichLegg/E+/Getty Images

Spraying foam and squirting cement

To print that person-sized tower, a Build-Drone carried expanding foam. This material rapidly expands and hardens when sprayed. As the drone flew in a slow circle, it sprayed the foam downwards to form layers. When it ran out of material, it flew away so a person could reload more foam or replace the drone’s batteries.

a tower of cylindrical white foam with the drone that printed it sitting next to it. In the foreground is Scan-drone, a smaller drone.
This tower stands 2.05 meters (6.7 feet) tall. It would loom over most grown-ups. The large robot, Build-Drone, sprayed the foam material. The smaller robot, Scan-Drone, checked its work. Sarah Lever photography, Autonomous Manufacturing Lab/UCL

This type of foam tends to thicken unevenly. So, while Build-Drone was reloading, a second, smaller drone surveyed the work. It was called Scan-Drone. It looked for places where the last layer was too thin or thick. Then it created a plan for the next layer to help even things out. This kept the tower straight and sturdy.

The foam tower was cool, but the team wasn’t done. In a second demo, Build-Drones and Scan-Drones worked together to make a cylinder about the size and shape of a large round cake. This structure was impressive because the drones laid down a cement-like material very accurately, to within millimeters.

The cement-like material was special, too. Researchers at the University of Bath in England crafted it specially for the project. It had to be light enough for the drones to carry. It had to be soft enough for the drones to squirt it out easily. Yet it also had to harden quickly into a strong layer, Kovac said. The drones laid down this material in a twisting path that made the structure even stronger.

The researchers also did several virtual demonstrations. In one, real drones flew the paths they would take to build a dome but didn’t print any material. Other computer simulations showed how teams of as many as 15 drones might work together to build different kinds of structures.

A new way to build

“Nobody had really done this before,” says Rahul Panat. He is a mechanical engineer and 3-D printing expert at Carnegie Mellon University in Pittsburgh, Penn., who was not involved in the research.

This was “an impressive demonstration,” says Andrea Tagliabue, who also wasn’t involved in the research. As a graduate student in robotics at MIT in Cambridge, Mass., Tagliabue works on control systems for drones. However, he notes that the researchers still have challenges left to solve before 3-D printing drones are useful in the real world.

For the first time, flying drones have 3-D printed structures. In the future, such drones might be able to build things or make repairs in hard-to-reach places.

Since these drones built structures inside a lab, they didn’t have to contend with wind or other outdoor disturbances. Also, cameras placed around the room could help track the drones’ positions and send them along the correct paths. Outdoors, the drones would have to navigate without this extra help, says Tagliabue. He also notes that the more drones there are, the more computation is needed to keep them all coordinated. If that computation takes too long, the drones can’t get the instructions they need in real time.

With work, these problems can be solved. Kovac is already planning to do tests outdoors. He also plans to build more complex structures. And he plans to make it so the drones can recharge and reload automatically.

If construction drones could work together like wasps or bees, they could construct buildings or make repairs in places that are tough for human crews and heavy machinery to reach. That may include disaster areas, the tops of tall buildings or even other planets, Kovac says. “There’s a lot of interest in building on Mars with robots.”

an illustration of teams of drones building structures alongside astronauts on a Marscape
In the future, teams of drones might build structures on Mars (illustrated). They won’t work on the moon, though. To fly, drones need air to push against, and the moon doesn’t have an atmosphere. Yusuf Furkan KAYA/Aerial Robotics Laboratory/Imperial College London and Materials and Technology Centre of Robotics, Swiss Federal Laboratories of Material Science and Technology (Empa)

Kathryn Hulick is a freelance science writer and the author of Strange But True: 10 of the World's Greatest Mysteries Explained, a book about the science of ghosts, aliens and more. She loves hiking, gardening and robots.

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