MIT researchers 3D print robot that can walk out of printer

Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) have created a technique for 3D printing robots that involves using both solid and liquid materials at the same time. Given its unique capabilities, the process allows for hydraulically driven robots to be fabricated in a single step. The research team demonstrated the concept by printing a six-legged robot that can crawl via 12 hydraulic pumps embedded within its body.

“Our approach, which we call ‘printable hydraulics,’ is a step towards the rapid fabrication of functional machines,” says CSAIL Director Daniela Rus, who oversaw the project and co-wrote the paper. “All you have to do is stick in a battery and motor, and you have a robot that can practically walk right out of the printer.”

Printable hydraulics uses an inject printer which deposits individual droplets of material that are each 20 to 30 microns in diameter. For each layer, the printer can use multiple materials, either a solid photopolymer or a liquid non-curing material.

“Inkjet printing lets us have eight different print-heads deposit different materials adjacent to one another, all at the same time,” MacCurdy says. “It gives us very fine control of material placement, which is what allows us to print complex, pre-filled fluidic channels.”

Printing both solid and liquid components can be difficult, the researchers admit. Printing test geometries, for example, required the team to experiment with different print orientations since the liquids often interfered with material that is supposed to solidify. This method was tedious, but MacCurdy points out that it’s really the only viable option, as the fuse-deposition model and laser sintering were much more challenging to work with both liquids and solids.

The researchers 3D printed a small hexapod robot that weighs about 1.5 pounds and is less than 6 inches long. To move, a single DC motor spins a crankshaft that pumps fluid to the robot’s legs. Aside from its motor and power supply, every component is printed in a single step with no assembly required.

The robot features several sets of “bellows” that are 3D printed directly into its body. The bellows use fluid pressure that is then translated into a mechanical force, allowing the robot to move. The hexapod has a 22-hour print time, but the researchers hope to improve on this time by advancing the hardware. The team believes that the applications are unique. For example, the robots can be produces quick, cheap and with few electronic components allowing them to be used in situations such as nuclear sites, where they are lethal to humans and radioactive enough to destroy conventional electronics.

Compatible with any multi-material 3D inkjet printer, “printable hydraulics” allows for a customizable design template that can create robots of different sizes, shapes and functions.

“If you have a crawling robot that you want to have step over something larger, you can tweak the design in a matter of minutes,” MacCurdy says. “In the future, the system will hardly need any human input at all; you can just press a few buttons, and it will automatically make the changes.”

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