Watch this robot construct the world’s biggest botmade building by itself

In just half a day, a new type of robot built an igloo-shaped building half the diameter of the U.S. Capitol dome—all by itself. In the future, such autonomous machines could assemble entire towns, create wacky Dr. Seuss–like structures, and even prepare the moon for its first human colony.

“It’s an impressive project,” says Matthias Kohler, an architect who studies autonomous construction at ETH Zurich in Switzerland, but was not involved in the work.

People have experimented with many approaches to autonomous construction, and the scientists—a team from the Massachusetts Institute of Technology’s (MIT’s) materials science and design focused Mediated Matter lab in Cambridge—weighed them all before designing their robot. Should their robot manufacture prefabricated parts in a distant factory? If it works on site, should it be crane-shaped? Should they create a swarm of builder drones? And what about the construction materials—should the robot assemble buildings from blocks? The scientists chose to go with a mobile, mechanical arm for easy customization and wider reach, and they decided to print buildings layer by layer, for more complex shapes.

Their solution consists of a large hydraulic arm on motorized tanklike treads (which you can watch at work, above). At the end of the arm is a smaller electric arm for finer movements, armed with a suite of sensors for positioning and stability control, along with swappable tools for welding, digging, and printing. The combined reach of the arms is more than 10 meters. The Digital Construction Platform, as it’s called, also carries solar panels and batteries.

To put the bot through its paces, the scientists programmed it to drive out of a warehouse and build an open-top dome using a method they developed called print-in-place: The electronic tip sprays a line of expanding foam that creates the outline of the structure. Layer by layer, the robot uses the foam to build up a hollow wall that serves as insulation and can later be filled with concrete and covered in plaster. To show its ability to print horizontally, the bot even added a bench to a wall. At 14.6 meters across, the structure is the largest building ever 3D-printed by a mobile robot, the researchers report today in Science Robotics. It’s also the fastest to be printed: 13.5 hours.

Several elements of the new bot made the feat possible. For example, the group made an “interesting leap forward” by putting lasers at the end of the arm to sense the tip’s position and help it counteract any unwanted movement in the rest of the arm, instead of keeping the whole thing perfectly stable, Kohler says. The technique, which has never before been used in a construction bot, allows the entire machine to be lightweight and have a huge reach. David Wilson, a mechanical engineer and the chief innovation officer at Bechtel in Houston, Texas (the contractor responsible for the Hoover Dam), says that the micro-macro manipulators and print-in-place method offer new potential.

Instead of making a square building, you can make a Dr. Seuss–looking building for the same cost.

Steven Keating, Massachusetts Institute of Technology

Aside from the safety advantages, autonomous 3D printing is faster and more precise than manual construction. It can also maximize building strength and efficiency by placing material only where it’s needed, and it simplifies planning and logistics. Steven Keating, the MIT mechanical engineer who led the project, imagines seeing the exact time, cost, and structural integrity of a building before even hitting “print.” Robots also allow for almost any design you can dream up. “Instead of making a square building,” he says, “you can make a Dr. Seuss–looking building for the same cost.”

The new robot can also build smaller structures from sand, compressed earth, metal chains (which it welds together), and even ice (which it deposits first as water). Such resourcefulness would be useful if it’s ever in a remote environment and has to build with whatever’s at hand. It can dig, sense various environmental cues including radiation (which could help it repair nuclear reactors), and print walls with variations in color or stiffness for further customization and efficiency. Keating would love to see the robot go to Mars, design a structure based on local ground and weather conditions, collect its own energy and materials, and then put up a house—or even a town.

For the moment, the building machine still needs a little help from its human friends. At one point, dew settled on the dome, causing a layer of foam to slide off the structure before it could fully adhere. Keating had to swap out the printing tip for a chainsaw and backtrack. But because print-in-place uses standard materials, the MIT researchers say it can be used alongside traditional construction techniques, paving a path toward code certification.

“We wanted to have the dream, the future vision,” Keating says, “and also something that we could implement right away.” Some people can hardly wait. The team has already been getting calls from NASA, the U.S. military, Google, and one guy who saw the dome and made a special request for a famous client: an underground basketball court.