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The robot flaps its 'fins' to swim like a manta ray. Li et al.

Applied physics

Fish-inspired robot leaves rivals in its wake

A manta-ray-like device moves twice as fast as other soft machines.

Swimming robots made of deformable materials tend to be slow. Tiefeng Li, Zhilong Huang and their colleagues at Zhejiang University in Hangzhou, China, built a robotic fish with a soft body, fins and a tail, using elastic polymers, a conductive hydrogel and silicone. A ‘muscle’ in the body makes it bend and straighten, causing the fins to flap like those of a manta ray to move the robot through the water (see video). When a voltage was applied to the robot, it swam at a speed of 6.4 centimetres per second, or 0.69 body lengths per second — double the speed of previous soft robot swimmers.

The robot carried its own onboard system for power and remote control, and was able to swim for three hours on a single battery charge.