Experimental 3D-printed octopus-like robot developed jointly by British and American scientists shows how to make underwater drones faster.
The robot, inspired by the ability of cephalopods to move rapidly by expelling water from inside their bodies, can accelerate a kilogram of payload from zero to 6mph in less than one second. This is equivalent to a Mini Cooper car carrying a 350kg load speeding from zero to 60mph in the same time.
"Man-made underwater vehicles are designed to be as streamlined as possible, but with the exception of torpedoes, which use massive amounts of propellant, none of these vehicles achieve speeds of even a single body length per second or accelerations of 0.1g, despite significant mechanical complexity,” said Gabriel Weymouth, lecturer for the Southampton Marine and Maritime Institute at the University of Southampton, the lead author of the study.
"Rigid bodies always lose energy to the surrounding water, but the rapidly shrinking form of the robot actually uses the water to help propel its ultra-fast escape, resulting in 53 per cent energy efficiency, which is better than the upper estimates for fast-starting fish."
The robot, developed jointly by the Southampton University researchers and a team from the Massachusetts Institute of Technology, has a 3D-printed skeleton supporting its hollow body. Apart from this structure, it doesn’t have any other moving parts or energy-storage components.
After sucking in water to its full capacity, the robot rapidly ejects the liquid with a powerful contraction, propelling itself forward. It achieves 2.6 times the thrust of a rigid rocket performing the same manoeuvre. The inner skeleton subsequently ensures the shape stays tight with its fins maintaining a straight trajectory.
The researchers calculate that making the robot bigger would improve its fast-starting performance, which could have applications in the development of artificial underwater vehicles that can match the speed, manoeuvrability and efficiency of their biological inspirations. The understanding this study provides could also have an impact in other engineering fields where drag is critical, such as aeroplane wing design.
The study was in Bioinspiration and Biomimetics.