Robotic jellyfish fueled by seawater

Posted by Kate Taylor

Engineers have built a robotic jellyfish, fueled by hydrogen, which they say could be used in underwater rescue missions.

Robojelly mimics the natural movements of a jellyfish, and is powered by heat-producing chemical reactions between the oxygen and hydrogen in water and the platinum on its surface.

The heat given off by these reactions is transferred to the artificial muscles of the robot, causing them to transform into different shapes and propel the robot forward.

"To our knowledge, this is the first successful powering of an underwater robot using external hydrogen as a fuel source," says Yonas Tadesse of Virgina Tech.

It means that Robojelly can regenerate fuel from its natural surroundings and therefore doesn't need any external power source - indeed, in theory, it could run forever.

A jellyfish moves by using circular muscles located on the inside of its umbrella-shaped main body. As the muscles contract, the bell closes in on itself and ejects water to propel the jellyfish forward. After contracting, the bell relaxes and regains its original shape.

The team mimimcked this using commercially-available shape memory alloys (SMA) - smart materials that 'remember' their original shape - wrapped in carbon nanotubes and coated with a platinum black powder.

So far, Robojelly has been confined to a tank, and hasn't yet taken a dip in the ocean - which would be rather more complicated. It's also currently running on electricity rather than hydrogen.

"The current design allows the jellyfish to flex its eight bell segments, each operated by a fuel-powered SMA module. This should be sufficient for the jellyfish to lift itself up if all the bell segments are actuated," says Tadesse.

"We are now researching new ways to deliver the fuel into each segment so that each one can be controlled individually. This should allow the robot to be controlled and moved in different directions," Tadesse continued.

There's a video below.