Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Science. 2020 Jan 17;367(6475):293-297. doi: 10.1126/science.aaz3358.
Variable feather overlap enables birds to morph their wings, unlike aircraft. They accomplish this feat by means of elastic compliance of connective tissue, which passively redistributes the overlapping flight feathers when the skeleton moves to morph the wing planform. Distinctive microstructures form "directional Velcro," such that when adjacent feathers slide apart during extension, thousands of lobate cilia on the underlapping feathers lock probabilistically with hooked rami of overlapping feathers to prevent gaps. These structures unlock automatically during flexion. Using a feathered biohybrid aerial robot, we demonstrate how both passive mechanisms make morphing wings robust to turbulence. We found that the hooked microstructures fasten feathers across bird species except silent fliers, whose feathers also lack the associated Velcro-like noise. These findings could inspire innovative directional fasteners and morphing aircraft.
不同于飞机，具有可变形羽片重叠的鸟类能够通过其翅膀实现变形。当骨骼运动以改变翅膀翼型时，连接组织的弹性会使重叠的飞羽被动重新分布，从而实现这一壮举。独特的微观结构形成了“定向维可牢”，当相邻的羽毛在伸展时分开滑动时，数千个裂片状的纤毛会与重叠羽毛的钩状分支随机锁定，以防止出现间隙。这些结构在弯曲时会自动解锁。通过使用具有羽毛的仿生混合空中机器人，我们展示了这两种被动机制如何使变形翅膀具有抗湍流的鲁棒性。我们发现，除了无声飞行者外，钩状微观结构可以固定各种鸟类的羽毛，而无声飞行者的羽毛也缺乏类似维可牢的相关噪音。这些发现可能会激发创新的定向紧固件和变形飞行器的灵感。
