"Robofly" is a generic name for any attempt at artificial flying machines on the size scale of houseflies, with wingspans about 3 cm (around an inch) and weights of about 100 milligrams. Several research efforts have focused on this challenge, often drawing inspiration from the biomechanics of real flies.
One of the earliest serious efforts to build a robofly was by the Biomimetic Millisystems Lab at the University of California at Berkeley. Started in 1998 and still ongoing, the project has not yet successfully built a real robofly, though some researchers did collaborate on what eventually became the first successful robofly. The team also made numerous important observations and discoveries about the mechanics of insect-scale flight. Finding that stainless steel lacked the necessary strength-to-weight ratio, the team began building prototypes out of carbon fiber in 2002.
The first successful robofly was built by Harvard engineer David Wood in 2007. It had a wingspan of 3 cm and a weight of 60 mg. Because the robofly lacked a control system, it was a tethered flight. Like many other robofly efforts, Wood's work has been funded by the Defense Advanced Research Projects Agency, DARPA. The United States military has been keen on developing roboflies for surveillance purposes, though they would have many other applications.
Building roboflies is difficult for several reasons: the biomechanics of fly flight are not perfectly understood, and the components necessary to build prototypes are so small and strong that special manufacturing techniques are needed to build them. For the successful Harvard robofly, laser micromachining of carbon fiber and polymer components was used, with precision to as little as two microns.
Because roboflies are so small, the surveillance information they could pick up in the field would likely be very low-resolution, probably similar to the visual signals picked up by real-life flies. Their small size would also prevent on-board communications with anything but very low power requirements. To save on actuator space, the robofly uses electroactive materials that bend in response to electric fields. As of 2008, researchers are still working on optimizing fly designs and getting their pre-existing designs off the ground.