A robot that mimics two of nature’s smartest swimmers could play a vital role in underwater exploration, its creators say. The device – inspired by the quick, efficient movements of squid and jellyfish – is ideal for probing sensitive ocean environments, including coral reefs, according to the team. Researchers based at the Universities of Edinburgh and Southampton say the robot’s lightweight design and soft exterior also make it suitable for work on underwater archaeological sites. The fascination for organisms such as squid, jellyfish and octopuses is growing enormously among scientists. Engineers are particularly fascinated because the creatures’ lack of supportive skeletal structure does not prevent them from outstanding feats of swimming. Dr Francesco Giorgio-SerchiChancellor's Fellow , School of Engineering Remarkably efficient Squid and jellyfish swim by periodically expanding and contracting a flexible internal cavity to generate a jet of fluid that propels them forward in a simple but remarkably efficient form of movement. Scientists use the so-called cost of transport – the ratio of power spent on propulsions compared to the weight and speed of an animal – to compare efficiencies of different species. Previous research has found that the Aurelia aurita jellyfish is the most efficient swimmer in nature, easily beating running and flying animals and bony fish. Engineers designed a simple but effective mechanism to power the robot. It is made from a rubber exterior membrane enclosing 3D-printed flexible ribs, which work together to form a propulsive bell. Copycat technique A small piston in the top half of the robot taps this bell repeatedly so that it expands and springs back. This mimics a jellyfish’s swimming technique, producing jets of fluid to propel the robot through the water. When the piston operates at the correct frequency – the natural resonance for the components – the robot can move at one body length per second and match the efficiency of the Aurella aurita jellyfish. The research, published in Science Robotics, demonstrates the benefits of using resonance for underwater propulsion. Resonance refers to large vibrations that occur when applying a force at the ideal frequency, like pushing a child on a swing. This phenomenon allows the robot to use very little power but generate large water jets to push itself forward. Mimicking biology Previous attempts to propel underwater robots with jetting systems have involved pushing water through a rigid tube. But the researchers wanted to take it further, so they introduced elasticity and resonance to mimic biology. Latest tests show the new robot is 10 to 50 times more efficient than typical small underwater vehicles powered by propellers and used for underwater exploration. There are still many challenges and exciting possibilities to explore with soft underwater robotic technologies. The team is now looking to extend the concept behind this robot to a fully manoeuvrable and autonomous underwater vehicle capable of sensing and navigating its environment. Dr Gabriel WeymouthAssociate Professor, School of Engineering, University of Southampton Related links Journal paper School of Engineering University of Southampton Publication date 21 Jan, 2021
