Researchers at Northwestern University are working on (PDF link) sub-millimeter robots that are capable of “walking” without complex hydraulics and other systems that would be impossible to build at such a small scale for now.
This 8-legged crab (+2 arms) can walk sideways, thanks to materials specially developed. The technology works by building legs that remember their original engineered shape. When heated up with a laser, the leg changes shape, allowing a motion to occur. Repeat the process, and you’ve got a “walk.”
The laser effectively controls how the robot moves, and it’s a way to offload some of the power sources and mechanics away from the robot. Depending on the material and laser strength, some designs could even “jump,” but this one moves relatively slowly.
This kind of technology is one of the ways tiny robots can move and is popular in the nano-robots world. It is believed that eventually, these devices will be able to operate in ordinarily inaccessible places, including the human body.
It has been long theorized that nanorobots would someday perform surgery tasks in a completely non-invasive way, such as destroying tumors or repairing tissue damage.
In science fiction stories, you could “back up” your body’s state and have such machines continuously restore it, making you effectively immortal. Fun, but let’s not get ahead of ourselves.