Many wings in nature are not rigid. Instead they flex and curve with the flow. Here researchers imitate that phenomenon with BILLY (Bio-Inspired Lightweight and Limber wing prototYpe). Using an evolutionary-style algorithm, BILLY determines its own optimal flapping characteristics to maximize performance. Its flexible membrane-style wing actually performs better than a rigid wing! Check out the end of the video for some flow visualization of the leading edge vortex. (Image and video credit: A. Gehrke et al.)