The team’s method of printing solid and liquid materials simultaneously allows them to create robotic structures that can be hydraulically powered. PhotoCredit: Robert MacCurdy/MIT CSAIL www.engineeringnews.co.nz 49 though at a more basic level each layer consists of a photopolymer, which is a solid, and a non-curing material, which is a liquid. “Inkjet printing lets us have eight different print-heads deposit different materials adjacent to one another, all at the same time,” Mr MacCurdy says. “It gives us very fine control of material placement, which is what allows us to print complex, pre-filled fluidic channels.” Another challenge with 3D printing liquids is that they often interfere with the droplets that are supposed to solidify. To handle that issue, the team printed dozens of test geometries with different orientations to determine the proper resolutions for printing solids and liquids together. While it’s a painstaking process, printing both liquids and solids is even more difficult with other 3D printing methods, such as fused-deposition modeling and laser-sintering. He adds that inkjet-printing is currently the best way to print multiple materials. The results To demonstrate their method, researchers 3D printed a small hexapod robot that weighs about 250 grams pounds and about 15cm 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. Among the robot’s key parts are several set of ‘bellows’ that are 3D printed directly into its body. To propel the robot, the bellows uses fluid pressure that is then translated into a mechanical force (as an alternative to the bellows, the team also demonstrated they could 3D print a gear pump that can produce continuous fluid flow). Lastly, the team 3D printed a silicone rubber robotic hand with our technique, and more on the engineering and resolution of the printers themselves,” says Rus, the Viterbi Professor of Electrical Engineering and Computer Science at MIT. “Printing ultimately takes as long as the printer takes, so as printers improve, so will the manufacturing capabilities.” fluid-actuated fingers, a “soft gripper” developed for Baxter. “The CSAIL team has taken multi-material printing to the next level by printing not just a combination of different polymers or a mixture of metals, but essentially a self-contained working hydraulic system,” says Hod Lipson, a professor of engineering at Columbia University. “It’s an important step towards the next big phase of 3D printing — moving from printing passive parts to printing active integrated systems.” MacCurdy envisions many potential applications, including disaster relief in dangerous environments. Many nuclear sites, for example, need to be remediated to reduce their radiation levels. Unfortunately, the sites are not only lethal to humans, but radioactive enough to destroy conventional electronics. “Printable robots like these can be quickly, cheaply fabricated, with fewer electronic components than traditional robots,” MacCurdy says. Looking ahead The team is eager to further build on their work. While the hexapod’s 22-hour print-time is relatively short for its complexity, researchers say that future hardware advances would improve the speed. “Accelerating the process depends less on the particulars of Believe it, Design it, 3D Print it! See how your prototype works in practice using Unitec Copy Centre’s new state-of-the-art 3D printers. MultiJet has unlimited benefits: » Versatile High Resolution UV Resin » Snap Fit Prototyping » Fluid Testing » Conceptual Design » Rapid Tooling Contact Lily Guo on copy3d@unitec.ac.nz www.unitec.ac.nz/copycentre EN048
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