A creepy robo-caterpillar that can sneak under doors has been developed. Researchers have demonstrated a caterpillar-like soft robot that can move forwards, backwards and dip under narrow spaces.
The caterpillar-bot’s movement, which is unnervingly similar to the real insects, is driven by a novel pattern of silver nanowires. They use heat to control the way the robot bends, allowing users to steer the robot in either direction.
The team have shown how the robot's movement could be controlled to the point where users were able steer it under a very low gap – similar to guiding the robot to slip under a door.
They believe their approach to "soft robot locomotion" could - with the addition of sensors or other technologies - potentially be used in search and rescue devices.
Yong Zhu, corresponding author of a paper on the work and the Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at North Carolina State University, said: "A caterpillar’s movement is controlled by local curvature of its body – its body curves differently when it pulls itself forward than it does when it pushes itself backward. We’ve drawn inspiration from the caterpillar’s biomechanics to mimic that local curvature, and use nanowire heaters to control similar curvature and movement in the caterpillar-bot.
“Engineering soft robots that can move in two different directions is a significant challenge in soft robotics. The embedded nanowire heaters allow us to control the movement of the robot in two ways.
"We can control which sections of the robot bend by controlling the pattern of heating in the soft robot. And we can control the extent to which those sections bend by controlling the amount of heat being applied."
How does it work?
The caterpillar-bot consists of two layers of polymer, which respond differently when exposed to heat. The bottom layer shrinks, or contracts, when exposed to heat.
The top layer expands when exposed to heat. A pattern of silver nanowires is embedded in the expanding layer of polymer. The pattern includes multiple lead points where researchers can apply an electric current.
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The researchers can control which sections of the robo-caterpillar nanowire pattern heat up by applying an electric current to different lead points. They can also control the amount of heat by applying more or less current.
Shuang Wu, first author of the paper and a postdoctoral researcher at NC State, said: "We demonstrated that the caterpillar-bot is capable of pulling itself forward and pushing itself backward. In general, the more current we applied, the faster it would move in either direction.
"However, we found that there was an optimal cycle, which gave the polymer time to cool – effectively allowing the ‘muscle’ to relax before contracting again. If we tried to cycle the caterpillar-bot too quickly, the body did not have time to ‘relax’ before contracting again, which impaired its movement.”
The researchers say they could control both forward and backward motion. They could also change how high the robot bent upwards at any point in that process.
A study paper, “Caterpillar-Inspired Soft Crawling Robot with Distributed Programmable Thermal Actuation,” is published in the open-access journal Science Advances. The paper was co-authored by Jie Yin, an associate professor of mechanical and aerospace engineering at NC State; Yaoye Hong, a Ph.D. student at NC State; and by Yao Zhao, a postdoctoral researcher at NC State.
