MFI - Micromechanical Flying Insect The goal of the micromechanical flying insect (MFI) project is to develop a 25 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. The MFI design is based on biomimetic principles to capture some of the exceptional flight performance achieved by true flies. The high performance of true flies is based on large forces generated by non-steady state aerodynamics, a high power-to-weight ratio motor system, and a high-speed control system with tightly integrated visual and inertial sensors. Design analysis shows us that piezoelectric actuators and flexible thorax structures can provide the needed power density and wing stroke, and that adequate power can be supplied by lithium batteries charged by solar cells. The MFI project started in May, 1998. In the first three years of the project, researchers concentrated on understanding fly flight aerodynamics and on analysis, design, and fabrication of MFI actuators, thorax, and wings. In August, 2001, the MFI prototype (with 1 wing) showed thrust forces on a test stand.