The common housefly is a marvel of aeronautical engineering. One reason the fly is a master at evading the handheld swatter is that its wings beat remarkably fast—about 200 times a second. To achieve this amazing speed, the fly makes use of complex biomechanics. Its wings are not directly attached to the muscles of the thorax. Rather the fly tenses and relaxes the muscles in rhythmic cycles that cause the thorax itself to change shape. That deformation in turn sets the wings to oscillating, much the way a tuning fork vibrates after having been struck. In this way, the fly manages to convert a tiny bit of energy into a whole lot of motion with very little effort.
Engineers, spurred by the miniaturization of computer circuits and micromanufacturing techniques, have done their best to build tiny flying machines that imitate this locomotive ability. The DelFly Micro, unveiled in 2008 by researchers at the Delft University of Technology in the Netherlands, weighs only three grams, has a wingspan of 100 millimeters and can carry a tiny video camera. The synthetic flier produced at the Harvard Microrobotics Laboratory is even smaller—it weighs in at a mere 0.06 gram (still more than four times heavier than a fly)—though once set in motion, the flier’s flight cannot be controlled. The real Achilles’ heel of these mechanical insects, however, is the amount of power they consume: no one has yet figured out how to pack enough energy into miniature batteries to supply the fliers with juice for more than a few minutes of flight.