The squid-like robot can navigate oceans without harming coral and fish (Credit: University of California, San Diego)

Soft robots, which can move around the ocean without harming sea life, are ideal for underwater exploration. However, they are rarely deployed because they are extremely slow and have a hard time maneuvering through the water. But that may change soon thanks to an innovative, self-propelling soft robot created by researchers at the University of California, San Diego.

For their design, the team, which included roboticists and experts in computer simulations and experimental fluid dynamics, drew inspiration from one of nature's fastest and most versatile swimmers — squids. The cephalopods use their strong muscles to draw in water and rapidly eject it through a siphon. By creating jets of water, they are able to move forward at rapid speeds.

The recently-developed robot, which resembles a paper lantern, was primarily built using soft materials, such as acrylic polymers. Its flexible ribs are attached to a circular plate at both ends. An adjustable nozzle fitted on one side helps draw in and release water each time the robot contracts. The resulting jets of water enable it to propel forward, similar to a squid. The other plate holds a waterproof compartment that can house a camera or other sensor, to record data. The bot also has its own power source, allowing it to float autonomously for long periods of time.

“Essentially, we recreated all the key features that squids use for high-speed swimming. This is the first untethered robot that can generate jet pulses for rapid locomotion like the squid and can achieve these jet pulses by changing its body shape, which improves swimming efficiency,” said Professor Michael T. Tolley, co-author of the study published in the journal Bioinspiration and Biomimetics on October 5, 2020.

Though the squid robot has not been tested in open waters, it successfully weaved around coral and fish in a large tank in the UC San Diego Birch Aquarium. What's more, the bot clocked an impressive speed of 18 to 32 centimeters per second, or about half a mile per hour. Though nowhere close to real squids, which travel between 23 and 25 miles per hour, it is faster than most other soft robots.

“After we were able to optimize the design of the robot so that it would swim in a tank in the lab, it was especially exciting to see that the robot was able to successfully swim in a large aquarium among coral and fish, demonstrating its feasibility for real-world applications,” said Caleb Christianson, who led the study as part of his Ph.D thesis.

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