Repairable cascaded slide-lock system endows bird feathers with tear-resistance and superdurability

Significance Bird feathers have aroused tremendous attention for their contributions to the unique flight capability of birds against wind and even through bushes. Many studies have attempted to explore the mechanism underlying feathers’ superdurability. However, it is not yet clear why feathers are so superdurable. In this study, we discovered and characterized the sophisticated cascaded slide-lock system of bird feathers, which is composed of flexible hooklets, a slide rail, and spines at the end of the slide rail as terminating structures. This finding demonstrates that the superdurability of bird feathers against tears originates from their cascaded slide-lock system, not from the “hook–groove system” proposed centuries ago.