Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) introduce the first-ever technique for 3D printing robots that involves printing solid and liquid materials at the same time. The new method allows the team to automatically 3D print dynamic robots in a single step, with no assembly required, using a commercially-available 3D printer. “Our approach, which we call ‘printable hydraulics,’ is a step towards the rapid fabrication of functional machines,” says CSAIL Director Daniela Rus. “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.” To demonstrate the concept, researchers 3D printed a tiny six-legged robot that can crawl via 12 hydraulic pumps embedded within its body. With “printable hydraulics,” an inkjet printer deposits individual droplets of material that are each 20 to 30 microns in diameter. The printer proceeds layer-by-layer from the bottom up. For each layer, the printer deposits different materials in different parts, and then uses high-intensity UV light to solidify all of the materials. The printer uses multiple materials, though at a more basic level each layer consist of a “photopolymer,” which is a solid, and “a non-curing material,” which is a liquid.