Researchers at America's Virginia Tech University have revealed a robot jellyfish fuelled by hydrogen, meaning it could, theoretically, never run out of energy.
The underwater machine, which was designed to aid nautical search and rescue operations, powers itself on chemical reactions between the oxygen and hydrogen in the water and the robot's platinum surface.
That reaction produces heat, which is then conveyed to the artificial muscles of the device, causing them to flex in ways similar to the movement of jellyfish.
Widespread use of hydrogen as fuel is seen as a vital development in future science, and although this is a small step the team are excited about their invention.
Lead author of the study, Yonas Tadesse, said: "To our knowledge, this is the first successful powering of an underwater robot using external hydrogen as a fuel source."
However, the team admit that there is still plenty of research to do in order for the robot jellyfish to work to its full capacity.
"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," said Tadesse.
Video of Robojelly in action can be seen below, showing the robotic jellyfish during testing in Virginia.
If you'd like to learn more about the project, the IoP paper on Robojelly can be downloaded here.
Watch Robojelly in action: