A feather’s barbs are pulled apart, in a manner that was replicated using  large-scale 3D-printed models(Credit: University of California San Diego) For decades, when people have wanted to stick two things together but later pull them back apart, Velcro has been the answer. In the future, however, the material may get some competition from bird feather-inspired technology. Composed of keratin (our fingernails are also made of the stuff), feathers have a central shaft going down the middle, with softer and skinnier barbs sprouting off to either side. Along the edges of those barbs are small structures known as barbules. Those barbules hook onto one another, holding adjacent barbs together (see the microscope image below). As anyone who has ever played with a feather will know, though, the barbs can still be pulled apart, then subsequently “zipped” back together. Tarah Sullivan, a researcher at the University of California San Diego, discovered that in birds of all sizes, the barbules are always spaced within eight to 16 micrometers of one another (a micrometer is one thousandth of a millimeter). Keeping this ratio in mind, she proceeded to create large-scale 3D...