Man-made 'octopus' fastest in water

New York: Scientists have developed an octopus-like robot which can zoom through water with ultra-fast propulsion and acceleration never before seen in human-made underwater vehicles.

Most fast aquatic animals are sleek and slender to help them move easily through the water, but cephalopods such as the octopus are capable of high-speed escapes by filling their bodies with water and then quickly expelling it to dart away.

Inspired by this, scientists from the University of Southampton, Massachusetts Institute of Technology (MIT), and the Singapore-MIT Alliance for Research and Technology built a deformable octopus-like robot with a 3D printed skeleton with no moving parts and no energy storage device other than a thin elastic outer hull.

The robot is capable of accelerating up to 10 body lengths in less than a second.

"Human-made underwater vehicles are designed to be as streamlined as possible but with the exception of torpedoes, none of these vehicles achieve speeds of even a single body length per second or accelerations of 0.1g, despite significant mechanical complexity," said lead author Gabriel Weymouth.

The 30 cm long self-propelling robot is inflated with water and then rapidly deflates by shooting the water out through its base to power its outstanding propulsion and acceleration, despite starting from a non-streamlined shape.

In the laboratory tests, the robot accelerated a one kg payload up to six mph in less than a second.

This is comparable to a 1,000 kg car accelerating from a standstill to 60 mph in one second - underwater.

"This performance is unprecedented in human-made underwater vehicles," the authors noted.

The findings could have applications in the development of artificial underwater vehicles that can match the speed, manoeuvrability and efficiency of their biological inspirations.

The study could also have implications in other engineering fields where drag is critical, such as airplane wing design, the study concluded.