NEWS
CARRY ON,
ROBOT
Researchers at North Carolina State University have created a cable car-like soft ring robot with the power to move 12 times its weight up steep aerial inclines.
Written by Kayt Sukel
Schematic of an autonomous soft twisted LCE ring robot that is curled around a track to convert self-flipping motion into linear movement along the track when exposed to constant infrared light perpendicular to the ring plane.
Credit: Fangjie Qi, North Carolina State University
THE FIELD OF ENGINEERING SEES GREAT PROMISE IN SOFT ROBOTS, or devices created with deformable materials, for biomedical, manufacturing, and search and rescue applications. Yet, their very softness can sometimes limit what they can do—their malleability often comes at the expense of strength and load capacity, as well as the ability to provide precise, controlled movement. Now, however, researchers from North Carolina State University (NC State) have created an autonomous soft robot, with a closed-loop twisted ring topology, that can follow an established track up inclines of 80 degrees.
Fangjie Qi, a doctoral student in the laboratory of Jie Yin, associate professor of mechanical and aerospace engineering at NC State, said when he and his colleagues first developed this soft robot made from ribbon-like liquid crystal elastomers (LCEs), they discovered it moved in a fascinating way with the application of heat.
“The very first time we put this robot on a heated surface, we observed it making these wavy motions,” Qi said. “It moved in this unique way that could propel it forward. And we wanted to convert that movement into a more controlled linear motion.”
Inspired by the idea of a screwdriver, which can convert a circular motion into a linear one to tighten a screw, the group placed the soft robot on a track to see what it would do. When they exposed the robot to an infrared light, as with the heat, the outside portion of the robot contracted, pulling the inside of the robot toward the light, which then contracted, and so on, to facilitate the robot’s linear movement along the track.
Once he saw how well the robot could move on the wire, much like a “cable car,” Qi was curious about how well it would do in different track scenarios. He wanted to push it to its limits.
“I wanted to challenge the robot and see what it could do,” he said. “That would help us understand its limitations.”
“The advantage of this design is that it can follow the track. Other kinds of soft robots move with different motions, and it’s very hard to keep their motion precise.”
— Fangjie Qi, doctoral student at North Carolina State University
Qi and colleagues put the ring-like soft robot through its paces. They discovered the 0.56-gram device could follow a variety of different-sized tracks, ranging from something as thin as a human hair to as thick as a drinking straw. It easily followed tracks in a straight line, but also managed more complex routes, with tracks configured as circles or even three-dimensional spiral patterns. The robot could also traverse obstacles on the tracks, including knots or bulges. It also demonstrated it could move up and down a slope with control—even up to 80 degrees in steepness. And, interestingly, it could carry nearly 12 times its own weight without a problem. Qi said the team was very impressed with all it could do.
“Eighty degrees is almost completely vertical,” he said. “We did not think it would be able to do that.”
Given the robot’s adaptability—and the fact that it overcomes some of the traditional limitations of soft robots— this type of design could potentially be used for a wide variety of applications, Qi added.
“The advantage of this design is that it can follow the track. Other kinds of soft robots move with different motions, and it’s very hard to keep their motion precise,” he said. “This robot could work in a scenario where you are trying to deliver a payload to something you cannot reach. If you can put a track in, the robot can follow—you could even maybe do something like this inside the human body.”
Beyond exploring potential applications for this type of soft robot, Qi said the research group is also considering designs that leverage materials beyond LCEs. In doing so, they could potentially create soft ring robots that move stimulated only by rays of sunlight, or other types of external energy sources.
“LCEs require very strong infrared light to move the robot. So, we are looking at other materials like graphene that can more efficiently convert light energy into this wavy motion,” he said. “With graphene, we could just use visible light to make the robot move.”
But, as the group continues to refine their design in the laboratory, Qi is hopeful that other engineers and roboticists will consider soft robot parts for bigger, complex designs.
“You could compose one part of a design with LCEs to get this motion—use this soft robot material as a component,” he said. “It could help deliver medicine or other cargo to places with more control. It opens up a lot of new possibilities for different designs and applications.”
Kayt Sukel is a technology writer and author in Houston.
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