There is no more rewarding moment for roboticists than when they first see their creations begin to twitch with a glimmer of life. For me, that moment of paternal pride came a year ago this month, when my artificial fly first flexed its wings and flew.

It began when I took a stick-thin winged robot, not much larger than a fingertip, and anchored it between two taut wires, rather like a miniature space shuttle tethered to a launchpad. Next I switched on the external power supply. Within milliseconds the carbon-fiber wings, 15 millimeters long, began to whip forward and back 120 times per second, flapping and twisting just like an actual insect's wings. The fly shot straight upward on the track laid out by the wires [see photo, ”Winged Victory”]. As far as I know, this was the first flight of an insect-size robot.

The experiment was the culmination of nearly a decade of work that began in the laboratory of my then-advisor, Ronald S. Fearing, a professor of electrical engineering at the University of California, Berkeley, and later migrated to my lab at Harvard. The little flying robot, we hope, will herald a new era of practical small-scale robot design.

The insectlike robots that my colleagues and I at the Harvard Microrobotics Laboratory are creating are intended to perform rescue and reconnaissance operations with equal ease. Once they can be fitted with onboard sensors, flight controls, and batteries, they will be freed from their tethers to the lab bench to nimbly flit around obstacles and into places beyond human reach.

For example, when a severe earthquake breaks the crust of the Earth and collapses buildings, rescue workers must frantically search for survivors while breathing air full of toxic particles and making their way through rubble-strewn passageways. They must do so on their own because our most sophisticated rescue robots falter and often fail when they encounter even mild clutter.

We envision a very different approach, in which emergency personnel disperse thousands of paper clip–size flying robots throughout a disaster zone. The tiny machines would detect signs of life, perhaps by sniffing the carbon dioxide of survivors' breath or detecting the warmth of their bodies. Though some flies might smash into windows or get stuck in corners, others would slip through cracks and under fallen crossbeams. Perhaps only three members of the swarm make their way to the survivors, where they perch and expend their remaining energy broadcasting their findings to rescue workers. They may have onboard radio-frequency transmitters to communicate short, low-bandwidth chirps, to be picked up by receivers installed around the perimeter of the site. Even if 99 percent of the robots are lost, the search mission would still be a success.

Designing a robotic insect is more complicated than simply shrinking a model airplane, however, because the aerodynamics that govern flight are entirely different on the scale of insects. The basics of insect-flight aerodynamics in different patterns of airflow first became clear in 1999, when Michael Dickinson, a biologist then at Berkeley and now at Caltech, built a 25â¿¿centimeter replica of a fly's wing and simulated the viscosity of air on a small scale by submerging the wing in a vat of mineral oil. It turns out that insects use three different wing motions to create and control the air vortices needed to generate lift.