Flexibility Optimization of 3D-Printed Bioinspired Flapping Wings

Hummingbird-inspired flexible wings were fabricated and tested with an electric flapping mechanism to explore the optimal design of the flexibility. The wing consisted of 3D-printed flexible radial shafts realizing spanwise torsion of the wing, an elastomeric membrane allowing the spanwise torsion by stretching, and a torsion-bar spring at the leading-edge base directly promoting the spanwise torsion. Measurement of lift and input power of the tethered flapping mechanism with different wing designs revealed that a favorable equilibrium between high lift and low power consumption can be achieved by the less-stiff torsion bar spring, stiff and tapered shafts, and the elastic membrane.