Objet 3D printing technology is being used at the University of Maryland's A. James Clark School of Engineering to produce a Robotic Samara - a micro unmanned aerial system (UAS). The school focuses on advanced propulsion, composites and hypersonics for potential alternate modes of flight for military applications:
Micro/Nano Unmanned Aerial Systems (UAS) are an emerging class of vehicles uniquely suited to performing covert missions. Autonomy is an essential aspect of the intended function of UAS, and development of a dynamic model will enable control and state estimation algorithm synthesis.
The 3D printing technology permitted very rapid turnaround of numerous prototypes, making the development process significantly faster (and cheaper, too). This was necessary as the project sought a unique flight mode based on nature:
To that end, a linear model for the heave dynamics of a mechanical samara (winged seed) in hovering ﬂight was identiﬁed from data collected external to the vehicle by a visual tracking system.
That's right - they mimicked the aerodynamics of Maple tree seeds. One can imagine the amount of trial and error involved in this venture - and how effective quick 3D prints would be as different designs were repeatedly attempted.