November 2001

Robo-Fly

Microfabrication

By David Talbot

It was almost Kitty Hawk for the micromachine crowd. Researchers at the University of California, Berkeley, achieved the first limited flight of the smallest-ever flapping-wing machine.

Berkeley's robo-fly has a wingspan of just three centimeters and weighs 300 milligrams-about the size of a rose petal. At that scale, the aerodynamic principles that keep airplanes aloft don't apply, so the researchers modeled the device on a fruit fly, which both flaps and rotates its wings hundreds of times per second. "If it was just flapping, we would have had this a couple of years ago," says project leader Ron Fearing. Actuators made of piezoelectric ceramic materials-which expand and contract when an electric charge is applied-move the robot's polymer wings.

The inaugural flight was just 30 centimeters and used one wing, while the robot was tethered to a metal boom. Albert Pisano, director of Berkeley's Electronics Research Lab, says the project is "paving the way for increased understanding of microscale aerodynamics, microscale mechanical systems and microscale fabrication methods." The U.S. Department of Defense, which funds the project, would like to use tiny flying machines for battlefield spying; eventually, they could act as weather sensors or air duct inspectors.
Fearing says that the robo-fly is not yet ready for untethered flight. He hopes it will be by 2003. "It's not quite Kitty Hawk yet," he acknowledges. Still, 30 centimeters is a lot at the insect scale; after all, the Wright brothers only made it 36 meters on their first flight.