Donald and his team of Duke University computer scientists have constructed a fleet of fully steerable microrobots small enough to move around on the head of a pin. Robots this small could some day explore brain tissue or manipulate delicate electronics.

The robots are about 250 microns long and 60 microns across. They are thinner than the width of a human hair, and you could line two of them end to end inside the period at the end of this sentence.

They look like spatulas that move around on a charged surface using small, spring-like steps similar to an inchworm's crawl. The microrobots have a long thin arm that can be lowered and used as a pivot for turning, allowing the machines to steer freely in any direction.

The microrobots will soon be put to work probing the architecture of animal brain cells. Donald is working with Duke neurobiologist Richard Mooney and physicist Gleb Finkelstein to put the little robots to work as drill rigs, driving electrodes mounted on the front of the robots into the cells. Eventually Donald hopes this technology can help neurobiologists understand how the human brain works.

"Just like when the car first appeared and people saw all sorts of uses for them, there are all kinds of applications for something that can move around and do tasks at a microscopic scale," Donald said. "These microrobots will be able to act as bulldozers, pickup trucks and construction machinery. They can drive around by themselves, and now we can control large groups of them."

Donald and his collaborators drive the microrobots in much the same way that young children drive the remote-controlled toy cars they use to terrorize parents and siblings.

"We send the same signal with instructions to the whole group of microrobots," he said. "Even though every robot gets the same message, we constructed multiple types of robots, which we call species. Each species has a slightly different physics, so they will all react to the instructions differently to carry out the task most efficiently."

Ronald Fearing runs a microrobotics lab at the University of California at Berkeley.

"I think of what professor Donald is doing as shrinking a factory to the size of a computer chip," Fearing said. "The microrobots are like little workers and machinery that can build things and fix things in the factory. This is really neat when you're talking about components that can't be handled by hand."

With so many potential applications, the future of the robots is unclear.

"The size is obviously a significant achievement," said Dan Popa, assistant professor of electrical engineering at the Automation and Robotics Research Institute at the University of Texas at Arlington. "But right now, what Donald has is mostly a curiosity. The next question is what these robots will be used for, and what that is is not entirely clear."

Popa said he could see Donald's microrobots being used to manipulate microscopic materials, a field called nano-manufacturing.

Although the microrobots are only following instructions right now, they are likely to start getting more intelligent in the future.

"My students are working on installing circuits that would allow the robots to do simple computations on their own," Donald said.

But there's no need to fear hordes of Donald's microrobots taking over the world just yet.

"They're carefully engineered so that they can't escape from the surface," he assured, "so there's nothing to worry about."

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