Burdocks and Velcro - Reversible adhesive structures

From nature ...

Many plant species produce bur fruits that get caught in the fur of animals. They serve for the long-distance dispersal of the seeds. The engineer George de Mestral was inspired by the fruit clusters of the greater burdock, which he repeatedly found in the fur of his dog, to conduct microscopic research. He discovered elastic hooks on the bracts that do not break off even when they are rigorously removed from hair or clothing.

... to technology

The idea for the textile hook-and-loop fastener, which can reversibly join materials, matured. In 1951, de Mestral filed a patent application for it under the name Velcro^®.

The fine hooks on one surface are much stronger than the loop fabric on the other, at least at the tip. When contact is made over a large area, the holding forces of the individual hooks add up. If the surfaces are pulled apart at an angle, the connections can be gradually loosened again with little force. Further developments of the principle have led to new patents in which, for example, mushroom- or club-shaped pins grip each other in the gaps.

Image captions

The infructescence of the greater burdock (Arctium lappa L.) bears tiny hooks...

...and was the model for the invention of hook-and-loop fasteners.

Great holding force due to simultaneous hooking of many hooks.

Little force is required to release the hooks step by step.

Text of the information board in the Botanical Garden