IEEE Spectrum reports that researchers from UC Berkeley are working on a drone that's physically smaller than a penny, and weights just 67 milligrams (which, according to WolframAlpha, is about the weight of a "typical large sand grain.") The tiny drone has its own IMU, and uses a set of 4 ion thrusters instead of rotors, which means it doesn't have any moving parts. As of now, the drone can only fly with a tether, but the researchers claim they see a path towards making the drone fully autonomous while still being able to carry a useful payload. Check out the video of the micro drone here. Although initial demonstrations of controlled flight will certainly be tethered and in an indoor laboratory setting, we envision the future ionocraft as a fully autonomous robot capable of outdoor flight. The path towards autonomy requires making strides in a number of interdependent categories, including: system development to allow for incorporation of more onboard computation, control, and sensing electronics; further engineering refinement of the EHD actuator to provide increased thrust density and efficiency at a lower operating voltage; and further development of both the simulation environment and the bench-scale flight testing setup to begin development of more robust controllers with high level functionality.