The Harvard microrobot can move up to two inches per second once it has folded itself into shape. | Samuel Felton/ Science/AAAS
Inspired by the traditional Japanese art form of origami, researchers have coaxed flat sheets of specialized paper and plastic to self-fold into complex machines that crawl and turn.
"We demonstrated this process by building a robot that folds itself and walks away without human assistance," said Sam Felton, a Ph.D. candidate at Harvard University's School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering. Felton is the lead author of a new report on the robots in the 8 August issue of the journal Science.
"Folding allows you to avoid the 'nuts and bolts' assembly approaches typically used for robots or other complex electromechanical devices and it allows you to integrate components like electronics, sensors, and actuators while flat," said Rob Wood, the Charles River Professor of Engineering and Applied Sciences Core Faculty Member at Harvard University's Wyss Institute for Biologically Inspired Engineering and the study's senior author.
Potential uses for these self-folding machines include search-and-rescue scenarios where they could be activated to navigate small tunnels or spaces. The fact that they could be shipped flat in large quantities, and then assembled on-site, makes them especially valuable. Other examples of their use include deployment into space for various forms of exploration or for self-folding shelters that rapidly assemble in disaster zones.
In the experiment, the researchers' robot self-assembled from flat sheets of paper and shape-memory polymers (plastics that change shape when heated above 100˚ Celsius) into which they had embedded electronics. The flat structure transformed into a dynamic, functional machine in about four minutes. It then crawled away at a speed of about 5.4 centimeters (or over 2 inches) per second, and it also turned — all without human help.
In a teleconference on 6 August, MIT's Daniela Rus replied to a reporter who asked how this technology might be used to improve robot production. "We might be able to reduce the design time of robots to a matter of hours and the fabrication cost to tens of thousands of dollars rather than millions of dollars."
Jesse Silverberg shows how to fold a Miura-ori, one of the origami patterns used in his team's study. | Jesse Silverberg, Arthur Evans, Lauren McLeod, Ryan Hayward, Thomas Hull, Christian Santangelo, Itai Cohen
For the last decade, the team that worked on this approach has been looking at ways to increase the complexity of robotic devices. They started by building folding-based devices at very small scales and then moved on to creating larger robots at larger scales.
"Traditional manufacturing requires expensive machinery, and 3-D printing is too slow for mass production, but planar [two-dimensional] composites can be rapidly built with inexpensive tools like laser cutters and etch tanks, and then folded into functional machines," Felton said. "Such manufacturing methods would be ideal for producing 100 to 1,000 units."
The researchers created their robot by using parts and materials that are readily available, such as self-folding hinges, as well as a 3-D-design software program called "Origamizer." The hinges feature embedded heating circuits that activate the folding. The placement of these hinges in the material, and the order in which they are triggered create a fold pattern that determines the final shape of the 3-D structure, the study reports.
In this case, the stiffness and type of the folds raised the robot's body, which propelled the legs to angle downward.
In a related advance, reported in the same issue of Science, Jesse Silverberg from Cornell University describes how his team also used origami-based engineering to design and build a new type of lightweight, ultra-tough programmable metamaterial. The researchers studied a specific type of zigzag folding pattern that has been used to efficiently pack solar panels for space missions. They used the pattern to create folded sheets and then devised a way to structurally alter the sheets so that they could control their mechanical properties. This would allow them to create metamaterials with desirable properties, such as strength or stiffness.
"When incorporated into more complex devices, these materials will enable on-the-fly transformation of mechanical function," explained Silverberg. "We envision combining these origami-inspired materials with computer-controlled actuators to build more complex machines, such as hardening shells, locked-in joints, and deployable barriers; ultimately this transformer technology will revolutionize the way we think about materials."