Making Workhorses Out of Minibots
It's about the size of an average bug, and it crawls along on track wheels at a top speed of about 20 inches a minute. At that rate, the tiny robot will never win a race against a cockroach. Nor is it very smart. About the only thing it can do to stay out of trouble is reverse its direction when it senses heat.
Despite its shortcomings as an ersatz insect, this mechanical mite has broken some records: Its creators at Sandia National Laboratories believe it's the world's smallest untethered robot. "This could be the robot of the future," says Edward Heller, one of the project's researchers.
This latest attempt in a continuing effort to create a mini autonomous robot vehicle -- MARV, for short -- measures barely a quarter of a cubic inch. Packed inside are three watch batteries for power, two tiny electric motors, a temperature sensor, and an 8K ROM (read-only memory). And the researchers are already looking for ways to provide more power and give it additional senses by adding a miniature camera, microphone, radio, and chemical microsensors.
Heller and his colleagues have big plans for their minibots. So far, little MARV has wended its way only through a minefield of nickels and dimes. But the engineers foresee MARV descendants scuttling about disabling land mines or detecting chemical and biological weapons. Equipped with sensors, they could roam through pipes detecting leaks or lurk in places where it would be almost impossible to place a sensor. Equipped with microphones, they might be the ultimate way to bug a building, creeping through the walls to listen in or report on human movement.
For its part, the Defense Dept. envisions using "swarms" of tiny robots to home in on sources of contagion or contamination far more quickly than a solitary searcher. Using a mathematical algorithm, also developed at Sandia, the method involves each robot continually informing all the others of its position and the strength and direction of the signal it's seeking. The flow of information allows each robot to refine the direction of the search, without being guided from a central source or being vulnerable to the intuitions of others.
The first MARVs, developed in 1996, were the clumsy cousins of the new generation. At one cubic inch, they were made from commercially available parts and contained all the necessary power, sensors, computers, and controls on board. Improvements over the next few years, such as building the bodies from printed circuit boards, pared them down to three-quarters of the original size.
To shrink the robots, Heller and his colleagues combined all the electronic parts into a "multichip module" built on a sliver of glass. The tiny, lightweight plastic bodies were made by a process called stereolithography. They are built up a thin layer at a time by hardening a coating of liquid polymer with a laser beam. The result has precise cavities to hold electronics, motors, batteries, and other parts. Another innovation was replacing conventional wheels, which provided limited mobility, with tracks. "I thought of how tanks can maneuver over large objects," says Douglas R. Adkins, the new minibot's mechanical designer.
The Sandia researchers still have a long way to go before exhausting the possibilities of miniaturization. Adkins is already working on a model with a larger drive pulley in an effort to extend the maximum range beyond the present 90 inches. "Hopefully we can get another 50% of travel," he says, acknowledging that this "will probably be our maximum until we find some better batteries."
Meanwhile, a radio communications system that will allow remote control of the robots is already being developed. Adkins believes radios and audio can be built in without any increase in the minibots' size.
If they get much smaller, the minibots could start running into trouble from real bugs -- becoming trapped in spider webs or gobbled by birds. Adkins concedes that their mortality rate might be high in an area with a lot of traffic. "I accidentally knocked one off of my bench, and it kept running," he says. "But if one gets stepped on, that's the end of it."
By Alan Hall in New York
Edited by Douglas Harbrecht