Artificial muscles.

Ray H Baughman has created artificial muscles ! He is a professor of chemistry at the University of Texas at Dallas. An excerpt...

Dr. Baughman's advance, reported in the current issue of the journal Science, is that his new muscle fibers double as fuel cells. Just like real muscles, they power themselves instead of relying on external electrical power. Chemical energy also delivers a greater bang.

And the details...

He and his colleagues have made two types of artificial muscles. One is a nickel-titanium alloy coated with platinum, which causes the fuel — currently methanol, but hydrogen or alcohol could work, too — to react with oxygen, producing heat. The metal shrinks; the muscle flexes. The artificial muscle can apply 100 times as much force as real muscle.
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The second artificial muscle, currently less powerful, is made of a sheet of nanotubes, tiny but superstrong cylindrical molecules of carbon. The reaction of fuel and oxygen releases electrical charges that repel each other and cause the nanotube sheet to expand.