Apr 6, 2016 | By Kira
Researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) have proven a first-of-its-kind method for 3D printing functional robots from solid and liquid materials at the same time. These hydraulic-powered robots can be made from commercially available 3D printers and ‘walk right out’ of the machine with virtually no assembly required.
The method, called “printable hydraulics,” answers two important issues in additive manufacturing technology and advanced robotics. First, until now, it has been extremely difficult and time consuming to incorporate hydraulic components (which use fluids to efficiently control mechanical forces) into robotics. Second, while many advanced 3D printers are equipped with multiple extruders and can therefore 3D print in a variety of materials—such as rigid and flexible, for example—3D printing with liquids is still notoriously difficult, and 3D printing solid and liquid together even more so.
CSAIL’s work, funded in part by the National Science Foundation, proves that it is possible to do both: 3D print with solid and liquid materials in a single object, and build hydraulic 3D printed robots in a single step.
The 3D printable hydraulics method, which we first covered in December 2015, consists of using an inkjet 3D printer to deposit individual droplets of material, which are 20-30 microns in diameter, layer-by-layer into a 3D object. Each layer consists of a photopolymer, which solidifies when exposed to UV light, and a non-curing liquid material. Furthermore, the solid material can be either rigid or flexible.
In order to determine optimal structures that would allow the curing materials to properly solidify without the non-curing materials getting in the way, the researchers 3D printed dozens of test geometries with different orientations. Through multiple, painstaking rounds of trial and error, they found that inkjet 3D printing was the best way to go:
“Inkjet printing lets us have eight different print-heads deposit different materials adjacent to one another, all at the same time,” said Robert MacCurdy, MIT mechanical engineer. “It gives us very fine control of material placement, which is what allows us to print complex, pre-filled fluidic channels. ...As far as I’m concerned, inkjet-printing is currently the best way to print multiple materials.”
To demonstrate the printable hydraulics method, CSAIL 3D printed two impressive and functional robots: a tiny six-legged 3D printed robot that can crawl via 12 hydraulic pumps, and a 3D printed soft rubber hand that can be used on the Baxter Research robot.
The small hexapod robot (which weighs 1.5 pounds and measures less than 6 inches long) is remarkable in that it requires only a single DC motor to power its movement. Other than that motor and its battery, every single component was 3D printed.
“Our approach, which we call ‘printable hydraulics,’ is a step towards the rapid fabrication of functional machines,” said 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.”
As MIT explains, the hexapod robot, which was 3D printed in only 22 hours, features several ‘bellows’ that are 3D printed directly into its body and can propel it forward using fluid pressure. In addition to the bellows, they 3D printed a gear pump that can produce a continuous flow of fluids and translate that into mechanical force, as well as a rotating crankshaft that actuates hydraulic transmission.
As for the soft robotic gripper, it was 3D printed from a silicone-rubber material with five, fluid-actuated fingers. Advancements in soft robotics, such as Rethink Robotics’ Baxter project or this pressure-sensing robotic hand, are a key step towards the future of Human-Computer Interaction (HCI), and being able to 3D print functional hydraulic systems into these soft robots will improve their development.
Not only is the printable hydraulic process compatible with any multimaterial inkjet 3D printer, but it can also be customized to 3D print robots of different sizes, shapes, and functions, making it a truly versatile and useful technology.
“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,” said MacCurdy. “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.”
The MIT CSAIL team proposed several real-world applications for these 3D printed robots, including being able to rapidly and cost-effectively 3D print hydraulic-powered, robots to send into disaster relief or dangerous environments.
In particular, the robots, which can be controlled via smartphone, would be valuable in exploring nuclear sites which are dangerous to humans and can disrupt conventional electronics. “Printable robots like these can be quickly, cheaply fabricated, with fewer electronic components than traditional robots,” said MacCurdy.
Ultimately, CSAIL’s printable hydraulics method proves that building functional robots from scratch does not have to be a time-consuming, costly, and labor-intensive process. Using commercially available 3D printing technology, hydraulically-powered robots could soon be walking right off the print bed and into real-world scenarios.
“3-D printing offers a way forward, allowing us to automatically produce complex, functional, hydraulically-powered robots that can be put to immediate use,” said Rus.
The MIT CSAIL research paper was recently accepted to this summer’s IEEE International Conferences on Robotics and Automation (ICRA). The paper's authors are Daniela Rus, Robert MacCurdy, PhD candidate Robert Katzchmann, and Harvard undergraduate Youbin Kim.
Watch the video below to see the 3D printed hydraulic robots in action:
Posted in 3D Printing Application
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