Footpads Stick to Vertical Surfaces

close up photograph of a green cricket on a green leaf

Biological Strategy

Great green bush-cricket

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Image: Chris Moody / Flickr / Some rights reserved

Attach Temporarily

Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate after landing.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Pads on bushcricket feet stick to vertical surfaces due to angled rods and a secreted viscous fluid.

“Like the gecko, the great green bushcricket (Tettigonia viridissima) is endowed with ‘sticky’ feet. It can walk on smooth vertical surfaces, and even upside down, with no trouble. Unlike the gecko, the bushcricket has smooth footpads. It relies not on van der Waals forces between the footpad and the substrate, but on design of the footpad itself. The cuticle of an insect’s footpad is comprised of the soft material found just below the exoskeleton elsewhere in the body. In the bushcricket, this soft material covers another cuticle layer: a thicket of fine, branching rods that slope forwards at an angle of around 60 degrees. As the foot presses down, the rods bend and the pad molds itself around the irregular surface below, achieving the maximum contact. As a final adhesive measure, the bushcricket secretes a viscous fluid onto its pads. It actually leaves footprints when it walks. This design has an advantage over the hairy-sole system used by geckos in that the bushcricket can easily lift its legs. It does not need to ‘peel’ its feet off the substrate.” (Courtesy of the Biomimicry Guild)

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