One of the programs that I teach is Michigan Birds. Part of this program focuses on feathers and their functions. Most students (and adults) have played with a feather at some point. One of the things that almost everyone has done with a feather is to peel it apart and then "zip" it back together.
Have you ever wondered why and how a feather can do this?
It all has to do with structure.
The larger feathers have a stiff central structure called a rachis.
One opposite sides of the rachis are flat structures called vanes. The vane are composed of stiff parallel structures called barbs. Each barb grows out from the rachis.
Each barb is further divided into smaller parts. Growing from opposite sides of a bard are small parallel growths called barbules. The barbules that emerge from one barb grow toward and interlock with the barbules from the next-door barb.
The barbuless are not the smallest part of the feather. On the sides of each barbule are even smaller structures called barbicels. These structures act like hooks and interlock with the barbicels on the adjacent barbule. When you feel the barbs of a feather apart, the barbicles become unlocked; when you "zip" the feather back together again, the barbicels lock back together.