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Robotic jellyfish fuelled by hydrogen invented

Engineers in the US say they have invented a hydrogen-powered robot that moves

through water like a jellyfish.

Development of the robot, nicknamed Robojelly, is in the early stages but

researchers hope it could eventually be used in underwater rescue operations.

Writing in Smart Materials and Structures, Yonas Tadesse said the jellyfish's

simple swimming action made it an ideal model for a vehicle.

Being fuelled by hydrogen means, in theory, it will not run out of energy.

Mr Tadesse, the lead author of the study, said: "To our knowledge, this is the

first successful powering of an underwater robot using external hydrogen as a

fuel source."

Artificial muscles

A jellyfish moves using circular muscles in the inside of its umbrella-like

bell.

As they contract, the bell closes in on itself and ejects water to propel

itself forward. When the muscles relax, the bell regains its original shape.

To replicate this, the vehicle uses shape memory alloys - materials that

"remember" their original shape.

These are wrapped in carbon nanotubes - tiny "straws" of pure carbon that are

renowned for their electrical properties - and coated with a platinum black

powder.

The robot is powered by heat-producing chemical reactions between the oxygen

and hydrogen in water and the platinum on its surface.

The heat from the reactions is transferred to the artificial muscles of the

robot, and reshapes them.

This means Robojelly can regenerate fuel from its surroundings rather than

running off an external power source or batteries.

The team, from Virginia Tech in the US, hope this could mean it need never run

out of energy.

Currently, the jellyfish flexes its eight bell segments at the same time but

there are plans to look at how to control each segment individually.

This would mean the robot could be more closely controlled and move in

different directions.

The study was sponsored by the US Office of Naval Research, which invests in

projects to benefit the US Navy and Marine Corps.