Researchers at the University of Washington and Stanford University have developed an insectlike robot with hundreds of tiny legs.
The Defense-funded team says it can carry more than seven times its own weight and move in any direction.
It weighs half a gram, measures about an inch long by a third of an inch wide, and is about the thickness of a fingernail; the team says one day similar robots could crawl through cracks to explore collapsed structures or collect environmental samples.
Technically, it's a centipede, with 512 feet arranged in 128 sets of four. Each foot consists of an electrical wire sandwiched between two different materials, one of which expands under heat more than the other. A current traveling through the wire heats the two materials and one side expands, making the foot curl.
The legs' surface area is so large compared to their volume that they can heat up or cool down in just 20 milliseconds.
Rows of feet shuffle along in this way at 20 to 30 times each second.
"It's one of the strongest actuators that you can get at the small scale, and it has one of the largest ranges of motion," says Karl Böhringer, a University of Washington professor of electrical engineering. "That's difficult to achieve at the small scale."
The device has had a varied career.
It was first built in the mid 1990s as a prototype part for a paper-thin scanner or printer. A few years later, the researchers modified it as a docking system for space satellites. Now, they've flipped it over so the structures that acted like moving cilia are on the bottom, turning the chip into an insectlike robot.
Modifications could probably take off 90 percent of the robot's weight, Böhringer said, and eliminate a significant fraction of its power needs.
As with other devices of this type, he added, a major challenge is the power supply. A battery would only let the robot run for 10 minutes, while researchers would like it to go for days.
Another is speed - right now, the UW robot moves at about three feet per hour.