Biologists wonder about some strange things, like how do dragonflies keep their heads on while having sex? Designers often need to connect two things together, either permanently or temporarily, and might benefit by asking the same types of questions.
George de Mestral, a Swiss engineer, did just that in 1941. He was intrigued by how cockleburs clung to his dog’s coat. He took this a step further, thinking about the idea of attachable and detachable fasteners, and invented Velcro. Cockleburs disperse their seeds by first clinging to an animal’s fur so the seeds can be transported elsewhere and then can be pulled off by the animal so they reach the soil to germinate.
Attachment mechanisms in nature are as diverse as nature itself. Each organism must deal with unique situations. Some insects need a mechanism to hold their wings together in flight or walk on a waxy plant surface. Plants, bacteria, mussels, and other organisms need to cling to rocks under moving water. Ivy and geckos need to climb walls. In some cases, these attachment mechanisms need to be reversible, and some need to allow for flexibility or movement so they don’t break when a force is applied.
The dragonfly head attachment mechanism is an example of a temporary attachment. A dragonfly’s head needs to swivel freely as it hunts for insects during flight and watches for predators. But there are several times when it needs to stabilize its head. One is when feeding on an insect and the other is when two dragonflies are having sex. The male holds onto the female’s head with the tip of his abdomen and puts a lot of tension on the head and neck area. To stabilize the head, there are fields of tiny hairs on the facing parts of the neck and head. Muscles pull these two fields together to allow interlocking and resulting friction that create the stabilization. To visualize this, think of putting two hairbrushes together. The shapes of these tiny hairs vary among species.
Here is a selection of other attachment strategies found in nature that might be useful to makers, depending on what you want out of your fastener:
- The four-part system that the English ivy uses to cling to walls can be a nightmare for building managers, but might teach us something for use in construction. Besides including an adhesive, the tiny root hairs dry out and scrunch into a spiral shape that locks them into place so tightly, that when trying to remove the ivy, pieces of the wall sometimes break off.
- Proteins exuded by blue mussels allow them to attach to rocks and other substrates underwater. This strategy has been mimicked for laminated wood products and surgical adhesives.
- Most insects have two sets of wings on each side of the body. During flight, these wings need to be attached together and some need to do so while allowing some lateral movement. There is a wide variety of attachment techniques, some of which are amazingly elaborate for being so tiny.
- The anchor of an oceanic species of algae called the bull kelp holds tight to substrates, but is flexible to allow the plant to manage the torque caused by waves and currents. This strategy has been mimicked for an underwater wave energy device.
Nature works at many scales, and some of these can transfer to our own designs. The dragonfly head-arresting mechanism works at the micro- and nano-scales, but the same principles might work at a larger scale. The kelp’s strategy occurs at the macro scale, but might work at smaller scales.
To see more attachment strategies, visit AskNature and click on the Explore button. AskNature was recently improved with a new look and easier searching for inspiration from nature, so if you haven’t visited it in awhile, take a look.
Sherry Ritter is a biologist, writer, and educator living in Montana. Before getting involved with biomimicry, she was a wildlife ecologist with state wildlife agencies in Wyoming and Idaho, and worked for the U.S. Forest Service. Biomimicry fits her life-long interest in organisms’ adaptations to survive.View more articles by Sherry Ritter