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'Living' robots powered by muscle

Montemano's team used rat heart cells to create a tiny device that moves on its own when the cells contract. A second device looks like a minute pair of frog legs.

"The bones that we're using are either a plastic or they're silicon based," he said. "So we make these really fine structures that mechanically have hinges that allow them to move and bend.

"And then by nano-scale manipulation of the surface chemistry, the muscle cells get the cues to say, 'Oh! I want to attach at this point and not to attach at another point'. And so the cells assemble, then they undergo a change, so that they actually form a muscle.

"Now you have a device that has a skeleton and muscles on it to allow it to move."

Under a microscope, you can see the tiny, two-footed "bio-bots" crawl around.