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Last Updated: Tuesday, 7 June, 2005, 12:45 GMT 13:45 UK
'Walking' octopus inspires soft robots
Octopus marginatus was the first "walking" species to be identified
The surprise discovery that octopi can "walk" along the sea bed on two tentacles has inspired scientists seeking to create of a new generation of soft, flexible robots.

Two species of octopus have been observed moving in an upright bipedal stride since the discovery was announced in March this year.

And scientists at the University of California at Berkeley believe they can develop artificial muscles for use in a new field of soft robotics using the studies of the octopus's movement.

"Each arm rolls along the suckers and pushes the animal back, and then the other arm touches down, rolls along the suckers, and pushes the animal back again," biologist Chrissy Hufford explained to BBC World Service's Science In Action programme.

"They flatten part of their arm like a tank tread, and roll backwards on it. They make a functional foot, even though they don't have an anatomic foot."

Rescue robots

While the octopus walks on two arms, the other six are pulled up under the body.

Importantly, the movement is much more fluid than in creatures with a skeleton.

"That's why it was such a surprise to see - because every other example of bipedal locomotion before had involved the support of a rigid skeleton," Dr Hufford added.

Soryu rescue robot
It is hoped the technology can feed into the creation of rescue robots
"As we know, octopi and other cephalopods don't have anything rigid in their arms - they are supported by bands of muscle... that allows them flexibility, but also some support."

This extreme flexibility and strength is of great interest to biologist Bob Full, who believes the octopus is an excellent model for how robots that move might be built without hard parts.

A prototype of a segment of what might become an octopus-like arm has already been built.

It is a "rolled" artificial muscle - a tube with a spring inside, into which electric current can be put.

The tube can shorten, lengthen, and bend in all directions.

"If you think about them linking end to end, you can imagine ultimately what results from that," Dr Full explained.

"You can get a segment that's longer and longer, and begins to look eventually very much like the arm of an octopus."

This artificial arm currently relies on metal for support - but Dr Full believes that eventually the support will come from bands of muscle alone, as in a real octopus.

As one band of muscle compresses, another is stretched, providing strength.

With no hard parts, the creature can squeeze through tiny spaces.

"That's the advantage of soft robotics," he added.

"Can you imagine how wonderful it would be to function as a search and rescue robot, to be able to go into areas - after an earthquake, after a car accident, during a fire - and move into spaces that no other robot could get into."

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