Squid-inspired robot swims with nature’s most efficient marine animals

Scientists at the University of Southampton and the University of Edinburgh have developed a flexible underwater robot that can propel itself through water in the same style as nature’s most efficient swimmer, the jellyfish Aurelia aurita.

The results, published in Scientific robotics, demonstrate that the new underwater robot can swim as quickly and efficiently as the squid and jellyfish that inspired its design, potentially opening up new possibilities for underwater exploration with its lightweight design and soft exterior.

Co-author Dr Francesco Giorgio-Serchi, Lecturer and Chancellor, School of Engineering, University of Edinburgh, said: “The fascination with organisms such as squid, jellyfish and octopus has tremendously increased because they are quite unique in this. their lack of supportive skeletal structure does not prevent them from achieving exceptional swimming feats. “

The “cost of transport” is used to compare the efficiency of species across biology, and by this measure the jellyfish is the most efficient animal in nature, easily beating running and flying animals and bony fish.

The new robot was developed at the University of Southampton and is the first submersible to demonstrate the benefits of using resonance for underwater propulsion. Resonance refers to large vibrations that occur when applying force at the ideal frequency, such as pushing a child on a swing. This allows the robot to use very little energy but generate large jets of water to push itself forward.

The simple but effective mechanism consists of a rubber diaphragm enclosing eight flexible 3-D printed ribs, which together form a “propulsion bell”. A small plunger in the top half of the robot taps this bell repeatedly to expand and then pop out again. This mimics the swimming technique of a jellyfish and produces the jets of fluid to propel the robot through the water. When the piston operates at the right frequency – the natural resonance of the components – the robot can move at body length per second and match the efficiency of the Aurella aurita jellyfish.

The latest tests show that the new robot is ten to fifty times more efficient than typical small submarine vehicles powered by propellers. This increased efficiency, combined with the added benefits of the robot’s soft and flexible exterior, would make it ideal for operating near sensitive environments such as a coral reef, archaeological sites or even in waters crowded with swimmers.

Co-author Thierry Bujard, a Masters student in Naval Architecture at the University of Southampton, designed and built the robot in a matter of months. Thierry said: “Previous attempts to propel underwater robots with jet systems involved pushing water through a rigid tube, but we wanted to go further, so we brought elasticity and resonance to mimic biology. I was really surprised by the results, I was confident. that the design would work but the efficiency of the robot was much higher than I expected. “

Dr Gabriel Weymouth, associate professor at the University’s School of Engineering, who oversaw the project, added: “The great advantage of using resonance is that we can get great vibrations from the propulsion bell. with a very small amount of power; we just need to warp it and let the elasticity and inertia do the rest, which has enabled us to unlock the effectiveness of the propulsion used by sea creatures that use jets for swimming.

“The last decade has seen a surge in research into flexible and biologically inspired robots, such as Boston Dynamic’s ‘Big Dog’, because they can be much more versatile than standard industrial robots. This research demonstrates that these concepts can also be applied to underwater robotics.

“There are still many exciting challenges and possibilities to explore with soft underwater robotic technologies. We are now looking to extend the concept behind this robot to a fully maneuverable and autonomous underwater vehicle capable of sensing and navigating its environment.”