Unlike the fly, which has cells packed with mitochondria to provide energy, the robots must obtain their power through a cable. High density, light weight fuel cells are not yet available for robots this small. A fruit fly can fly up to 9 hours without rest based on its stored energy, a lofty goal for a small robot.
The fly has a more efficient wing hinge made of resilin. The fly thorax has elastic properties that capture energy of each up stroke and downstroke and uses that energy to partially power the return stroke. The robot has hinges with some elastic properties but they are less efficient than resilin and not as resistant to wear.
The fly has a pin-head sized brain and ganglia in the thorax that control flight. The Harvard team is working on a microprocessor that can be mounted on the robot. The current robot is controlled by an external computer.
Miniaturization in manufacturing makes it possible to produce insect sized robots. Insects help provide the inspiration for the robots and provide working biological models for study.