This robotic fish is inspired by lionfish James Pikul

Soft robots can already swim like fish and squeeze damaged hearts to keep blood pumping. But now there is a robotic fish that combines both.

Robert Shepherd at Cornell University in New York and his colleagues have developed a robot that is powered by its own artificial circulatory system.

The robot, whose design was inspired by a lionfish, can fan its pectoral fins and swim at a speed of more than 1.5 body lengths per minute, which is around 15 centimetres per minute or around 0.01 kilometres per hour.


Shepherd says the swimming speed can be improved. “1.5 body lengths per minute – that’s very slow, kind of like a loiter for a fish,” he says.

It is powered by flow batteries, systems that consist of two electrodes and a liquid electrolyte that flows between them. As the liquid moves around, it powers pumps present in the robot’s tail, dorsal and pectoral fins.

Flow of the liquid also increases pressure in certain areas. The mechanism is like inflating a balloon, says Shepherd, which causes the shape and stiffness of parts of the robot to change. The fluid, for example, inflates one side of the robot fish’s tail and causes the other to compress, resulting in a bending motion.

To allow for a flexible range of movement, electrodes in the robotic fish were made from bendable nickel wire mesh. The robot’s watertight exterior was made from silicone.

The design means that it can store a large amount of energy, says Shepherd. The team calculates that it could swim continuously for up to 36 hours, although it was only tested for a couple of hours.

The team will next work on improving the power of the robot’s movements.

Journal reference: Nature, DOI: 10.1038/s41586-019-1313-1