Enlarge Image MIT CSAIL

In a giant step towards rapid robot fabrication, researchers at MIT's Computer Science and Artificial Intelligence Laboratory have developed the first ever technique for simultaneously 3D printing with solids and liquids.

And to demonstrate how well it works, they have developed adorable little robots that waddle about on little hydraulic legs.

"Our approach, which we call 'printable hydraulics,' is a step towards the rapid fabrication of functional machines," said CSAIL Director Daniela Rus, who oversaw the project and co-wrote the paper, in a statement. "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."

The printer first starts with the solid materials, building them up layer by layer, curing them with UV light before adding the liquid that powers the hydraulic bellows that operate the legs. This overcomes several challenges previously associated with 3D printing liquids.

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

The six-inch hexapod robot designed to prove the concept takes 22 hours to print, which isn't long considering its complexity.

It moves using 12 hydraulic bellows that are printed right onto its body. These are powered by a single DC motor that spins a crankshaft that controls the pressure of the fluid in the bellows, translating it into mechanical force that moves the legs, allowing the little robot to waddle forward.

The team also built a silicone-rubber had for MIT's Baxter robot that uses liquid to move the fingers into and out of a gripping position.

"Printable robots like these can be quickly, cheaply fabricated, with fewer electronic components than traditional robots," MacCurdy said.