Hook and loop fastener

Hook-and-loop fasteners, hook-and-pile fasteners or touch fasteners, commonly known as "velcro", consist of two components: typically, two lineal fabric strips (or, alternatively, round "dots" or squares) which are attached (sewn or otherwise adhered) to the opposing surfaces to be fastened. The first component features tiny hooks; the second features even smaller and "hairier" loops. When the two components are pressed together, the hooks catch in the loops and the two pieces fasten or bind temporarily during the time that they are pressed together. When separated, by pulling or peeling the two surfaces apart, the strips make a distinctive "ripping" sound.

The original hook-and-loop fastener was conceived in 1941 by Swiss engineer George de Mestral. The idea came to him one day after returning from a hunting trip with his dog in the Alps. He took a close look at the burrs (seeds) of burdock that kept sticking to his clothes and his dog's fur. He examined them under a microscope, and noted their hundreds of "hooks" that caught on anything with a loop, such as clothing, animal fur, or hair. He saw the possibility of binding two materials reversibly in a simple fashion if he could figure out how to duplicate the hooks and loops. Hook and Loop is viewed by some like Steven Vogel or Werner Nachtigall as a key example of inspiration from nature or the copying of nature's mechanisms (called bionics or biomimesis).

Originally people refused to take de Mestral seriously when he took his idea to Lyon, which was then a center of weaving. He did manage to gain the help of one weaver, who made two cotton strips that worked. However, the cotton wore out quickly, so de Mestral turned to synthetic fibers. He settled on nylon as being the best synthetic, which had several advantages: it doesn’t break down, rot, or attract mold, and it could be produced in threads of various thickness. Nylon had only recently been invented, and through trial and error de Mestral eventually discovered that, when sewn under hot infrared light, nylon forms small hook shapes. However, he had yet to figure out a way to mechanize the process, and to make the looped side. Next he found that nylon thread, when woven in loops and heat-treated, retains its shape and is resilient; however, the loops had to be cut in just the right spot so that they could be fastened and unfastened many times. On the verge of giving up, a new idea came to him. He bought a pair of shears and trimmed the tops off the loops, thus creating hooks that would match up perfectly with the loops in the pile.

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