Feathers of a bird stick together underactuation and directional adhesion in avian wing morphing

Meeting Abstract

53-6  Saturday, Jan. 5 11:15 – 11:30  Feathers of a bird stick together: underactuation and directional adhesion in avian wing morphing MATLOFF, LY*; CHANG, E; STOWERS, AK; FEO, T; JEFFRIES, L; THOMPSON, C; LENTINK, D; Stanford University; Stanford University; Stanford University; Smithsonian Institution, Division of Birds; Stanford University; Stanford University; Stanford University lmatloff@stanford.edu

Birds morph their wings through continuous shapes to attain maximal flight performance and maneuverability. This seamless morphing happens through the movement of feathers, yet how they work together in a wing capable of robust flight is heretofore unknown. To gain insight into the underlying mechanisms that coordinate flight feathers, we take a multi-scale approach, measuring feather interactions at different hierarchical levels of organization. Kinematic measurements of common pigeon wings found that feathers move linearly with respect to the wrist angle during wing morphing, showing that feather coordination is an underactuated system controlled by skeletal motion. We then investigated neighboring feather interactions by measuring of pairs of feathers and the forces they exert on each other when separating in different directions. Only in the direction of wing extension, motion was locked, acting as end stops preventing separation. Microstructures on the interacting surfaces contribute to the directional adhesion effects. High-resolution micro computed tomography scans captured the curved morphology of the dorsal rami on the leading edge of flight feathers. We developed underactuated feathered robotic wings which we test in a wind tunnel under laminar and turbulent flow profiles as well as on a robotic platform in free outdoor flight. Together, underactuation and directional adhesion enable feathers to work in conjunction to coordinate wing morphing.

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