Like a live animal baby, MIT's latest robot can be pulled whole from its womb, be given a smack on the butt, and then crawl off on its own—if you substitute "3-D printer" for "womb," and "drop in a motor and battery" for "slap on the rear," that is.
The little six-legged robot is remarkable because all its parts are printed at the same time. And it's even more remarkable because the design is hydraulic, which means that some parts are solid, and other liquid, and the liquid needs to be sealed in to maintain pressure. This was achieved by using several print heads, each one laying down a different material as the printer builds up the robot, a layer at a time. And it can be done in a regular, commercially available printer.
"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," says MIT Computer Science and Artificial Intelligence Lab director Daniela Rus.
The problem with printing liquids is that it's messy. This means that the printed object needs to be manually cleaned up by a human hand, making it impractical for mass production. This robot gets around this by using inkjet printing to deposit solid and liquid at the same time. The liquid drops are on the order of microns in size, and the solid parts are cured by UV light as each layer is completed. The team had to carefully design the print process to stop the liquid parts interfering with the solid parts before they are cured, and the whole process is somewhat convoluted, but the big breakthrough is that a working hydraulic machine can be printed, all without human intervention. This brings speed and flexibility.
"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," co-author Robert MacCurdy told MIT News. "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."
Currently, the robot takes 22 hours to print, although better, higher-resolution printers could speed this up. And if printed machines are to be useful in future, speed will be key. MacCurdy see the robots as useful in disaster relief. In a dangerous environment like a nuclear meltdown, you could throw these robots at the problem, creating them on site as needed. "Printable robots like these can be quickly, cheaply fabricated, with fewer electronic components than traditional robots," he says.
Perhaps a next step could be to print a working 3-D printer. The RepRap is a printer that can already self-replicate by making a kit of itself, but assembly is required. It's easy to joke about a robot revolution where our future overlords reproduce themselves, but imagine if you could print a fully-assembled RepRap. Once a single person in your neighborhood had one, you could print new ones, at exponential speeds, until everybody in the neighborhood had one. That sounds like the kind of robot revolution we can get behind.