Talk about life imitating art, or in this case, the other way around: Researchers from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have taken inspiration from an ancient Japanese form of paper craft to make their latest technological wonder – a soft robot that moves just like a snake. The results of their research are published in the journal Science Robotics.
Kirigami – which comes from the Japanese words “kiru” (to cut) and “kami” (paper) – is a form of paper craft that relies on the “skillful cutting of paper.” In the study, the researchers looked at kirigami to create the soft robotic scales of the robot.
The scales change their properties, depending on the movement of the robot. If the skin is stretched, it transforms into a 3D texture which is better suited to grip the ground, much like how a snake does in real life.
“There has been a lot of research in recent years into how to fabricate these kinds of morphable, stretchable structures,” explained Ahmad Rafsanjani, the paper’s first author and a postdoctoral fellow at SEAS. “We have shown that kirigami principles can be integrated into soft robots to achieve locomotion in a way that is simpler, faster and cheaper than most previous techniques.”
Another fact that makes this robot better than other soft robots is its simplicity. The SEAS model only needs one motor to move, whereas other would require several motors. How it moves, therefore, is driven solely by the kirigami-inspired scales and their inherent grip.
The robot started out with a simple, flat plastic sheet, which researchers cut using a laser cutter. For the study, they tried out different shapes and sizes and tested these until they reached their desired result – a trapezoid scale which closely resembles actual snake scales. This cut geometry, Rafsanjani added, was tapped to demonstrate the locomotive properties of the kirigami-inspired skins. “Moving forward, these components can be further optimized to improve the response of the system,” he said.
After they’ve settled with the shape of the scales, they wrapped the sheet around an elastomer actuator. The actuator is a silicone-based tube “which expands and contracts with air like a balloon.” When the actuator expands, the kirigami cuts pop-out like small spikes and form a rough surface that can latch itself to the ground. Once the actuator deflates, the cuts start to fold, and those cuts that are attached to the ground launch the robot forward.
Both tethered and untethered types were tested. The tethered version had a cord to supply air into the crawler and inflate it. The untethered prototype, on the other hand, had controls, actuators, sensors, and a power supply attached to make it fully autonomous.
In the long run, researchers believe soft robots like these could be used in various fields that may be dangerous to humans, such as exploration and search-and-rescue. Moreover, if this could be produced in miniatures, this may even help with challenging medical procedures such as keyhole surgeries. (Related: Humans are embracing the rise of the “robosurgeon” but new studies suggest they are NOT better than human surgeons.)
“We believe that our kirigami-based strategy opens avenues for the design of a new class of soft crawlers,” quipped Katia Bertoldi, the senior author of the study.
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