Sticky Business

Sticky Business

Scientists study biological systems to understand how nature works, perhaps with the ultimate aim of understanding man’s place in it. A side benefit of observing natural systems, however, are the marvels of engineering that non-humans animals possess. Insects are perhaps the most remarkable of creatures when it comes to movement, whether flying, crawling or hanging upside down.

The stick insect sometimes needs to hang upside down under leaves, and climbs vertically along branches. How does this creature accomplish adherence when upside down and ‘normal’ striding when right side up? Turns out a complex system of adherence explains these incredible feats – no pun intended – of travel.

Research from the Cambridge Department of Zoology breaks it down for us nonscientists in a three point system. But first it’s helpful to understand that stick bugs have heel pads and toe pads, each with their own independent friction features: toe pads are sticky, while heel pads are not sticky. The heel pads have three separate features to regulate grip strength.

First, rounded hairs – both on the pad itself and of the hairs. This feature means that as pressure is increased, surface area instantly increased as well. Second, varying lengths of hairs. This feature allows for more hairs to come in contact with the surface as pressure increased. Third, there is a back-up system with hairs that make side-contact when the most pressure is applied. Without any pressure, there is no friction and therefore no “stickiness.”

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