World's smallest robot

Dartmouth researchers built what they claim is the world's "smallest untethered, controllable robot." Built from micro-electromechanical systems (MEMS) fabricated using processes similar to the way integrated circuits are manufactured, the microbot is approximately as wide as a human hair and about 250 micrometers long. (one micrometer=1/1000 of a millimeter) From Dartmouth News:
 ~News Releases 2005 09 Images Tiny-Closeup"It's tens of times smaller in length, and thousands of times smaller in mass than previous untethered microrobots that are controllable," says (researcher Bruce) Donald. "When we say 'controllable,' it means it's like a car; you can steer it anywhere on a flat surface, and drive it wherever you want to go. It doesn't drive on wheels, but crawls like a silicon inchworm, making tens of thousands of 10-nanometer steps every second. It turns by putting a silicon 'foot' out and pivoting like a motorcyclist skidding around a tight turn."

The future applications for micro-electromechanical systems, or MEMS, include ensuring information security, such as assisting with network authentication and authorization; inspecting and making repairs to an integrated circuit; exploring hazardous environments, perhaps after a hazardous chemical explosion; or involving biotechnology, say to manipulate cells or tissues.
Link to Dartmouth News, Link to an article I wrote in 2003 about UC Berkeley's MEMS robot