A Burr's Grip, a Strap's Snap

When you press a bag's strap shut and hear a rip as you pull it open, you may be using a hook-and-loop fastener. This tool holds two surfaces together without glue. Its story began with a plant part that many walkers would rather brush off: a prickly burr.

A Ride for Seeds

Burdock plants grow burrs that hold seeds. Each burr has many small hooks. When an animal brushes past, the hooks catch in its fur. The animal may carry the burr away before it drops off. As a result, the seeds can reach a new place to grow. The burr clings because its hooks catch, not because it is sticky.

In 1941, Swiss engineer Georges de Mestral noticed burrs stuck to his clothes and his dog's fur after a walk. He examined the burrs under a microscope, a tool that makes tiny things look bigger. Seeing their hooks gave him an idea: he could copy this grip to make a new kind of fastener.

Making a Reusable Grip

Copying the shape was not enough. A useful fastener needed hooks that would hold firmly but still bend without breaking. After years of work, de Mestral developed a fastener using nylon, a strong material that could form flexible hooks. Flexible means able to bend.

One strip of the fastener has tiny hooks. The other has many soft loops. Pressing the strips together pushes the hooks into the loops. Like a burr catching on fur, the hooks catch on something they can curl around. Many small catches work together to hold the strips shut.

Pulling the strips apart peels the hooks out of the loops. Because the hooks can bend and return to shape, the strips can be pressed together again. A burr helps a plant's seeds travel, while the human-made fastener helps people close things. The jobs are different, but the gripping idea is much the same.

Picture a close-up drawing of the two strips. Its caption could read, "Tiny hooks catch soft loops." The drawing would show how a tool for closing bags uses the same kind of grip as a traveling burr.