Wing shapes take flight Birds can dynamically alter the shape of their wings during flight, although how this is accomplished is poorly understood. Matloff et al. found that two mechanisms control the movement of the individual feathers. Whenever the skeleton moves, the feathers are redistributed passively through compliance of the elastic connective tissue at the feather base. To prevent the feathers from spreading too far apart, hook-shaped microstructures on adjacent feathers form a directional fastener that locks adjacent feathers. These features are found across a range of bird sizes; however, because the detachment of the hooks is noisy, they are notably absent in silent fliers, such as barn owls. Science, this issue p. 293 Hooks on neighboring feathers let them slide apart and lock into position, allowing birds to gradually alter their wing shape. 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.

中文翻译：

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飞羽如何粘在一起形成连续变形的翅膀

翅膀的形状飞行鸟类可以在飞行过程中动态地改变翅膀的形状，尽管人们对这是如何实现的知之甚少。马特洛夫等人。发现有两种机制控制着个体羽毛的运动。每当骨骼移动时，羽毛都会通过羽毛基部弹性结缔组织的顺应性被动地重新分布。为了防止羽毛分开太远，相邻羽毛上的钩状微结构形成一个方向扣，锁定相邻羽毛。这些特征可以在各种大小的鸟类中找到；然而，因为钩子的分离是嘈杂的，它们在无声的飞行物中明显不存在，例如谷仓猫头鹰。科学，这个问题 p。293 相邻羽毛上的钩子让它们滑开并锁定到位，允许鸟类逐渐改变它们的翅膀形状。与飞机不同，可变羽毛重叠使鸟类能够变形翅膀。他们通过结缔组织的弹性顺应性来完成这一壮举，当骨骼移动以改变机翼平面时，结缔组织被动地重新分布重叠的飞羽。独特的微观结构形成“定向魔术贴”，这样当相邻的羽毛在伸展过程中滑开时，重叠羽毛上的数千根叶状纤毛可能会与重叠羽毛的钩状分枝锁定，以防止出现间隙。这些结构在屈曲期间自动解锁。使用带羽毛的生物混合空中机器人，我们展示了这两种被动机制如何使变形机翼对湍流具有鲁棒性。我们发现钩状微结构将羽毛固定在鸟类身上，除了沉默的飞行者，它的羽毛也没有类似魔术贴的噪音。这些发现可以激发创新的定向紧固件和变形飞机。