How the insect world’s strongest suction power could help University of Cambridge create bio-inspired products

If you’ve ever stuck something to a window using suction cups, only to discover it falls off, then you’ll appreciate the extraordinary staying power demonstrated by the aquatic larvae of the net-winged midge.

With suction organs that boast the highest attachment strength ever recorded in insects, they are able to rapidly detach and reattach to underwater rocks in rapid alpine rivers flowing at up to three metres a second.

So strong are these organs that it takes forces more than 600 times their body weight to dislodge them.

Now some suitably impressed University of Cambridge researchers have used scanning electron microscopy, confocal laser scanning microscopy and X-ray computed micro-tomography (micro-CT) to uncover the secrets of the larvae’s specialist suction power.

The findings, which reveal the internal structure of the suction organs in three dimensions, could help engineers develop ‘bio-inspired’ suction cups.

Victor Kang, a PhD student in the University of Cambridge’s Department of Zoology and first author of a paper published in the journal BMC Zoology, said: “The force of the river water where the larvae live is absolutely enormous, and they use their suction organs to attach themselves with incredible strength. If they let go they’re instantly swept away

“They aren’t bothered at all by the extreme water speeds – we see them feeding and moving around in all directions.”

The same couldn’t be said for the researchers who waded into the fastest flowing parts of alpine rivers near Innsbruck, Austria, and found it hard to stay upright.

Meanwhile, the two species of larvae – Liponeura cinerascens and Liponeura cordata – grazed without any trouble on the underwater rocks.

The researchers found a central piston, controlled by certain muscles, is used to create the suction and create a very tight seal with the surface of the rock.

Helping to keep the larva in place is a dense array of tiny hairs in contact with the rock surface.

A tiny slit on the suction disc pulls it open, enabling the organ to detach - a mechanism not seen before in any biological system.

Dr Walter Federle, an expert in comparative biomechanics at the University of Cambridge who led the study, added: “These natural structures have been optimised through millions of years of evolution. We want to learn from them to create better engineered products.”

Existing artificial suction cups only work well on smooth, clean surfaces, like a car windscreen or a clean-room facility.

But working with colleagues at the Institute of New Materials, in Saarbrücken, Germany, the researchers hope to develop much more effective options.

“By understanding how the larvae’s suction organs work, we now envisage a whole host of exciting uses for engineered suction cups,” said Dr Federle. “There could be medical applications, for example, allowing surgeons to move around delicate tissues, or industrial applications like berry picking machines, where suction cups could pick the fruit without crushing them.”

This research was funded by the EU Horizon 2020 research and innovation programme under a Marie Skłodowska-Curie grant, and by the EPSRC.

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Pictured: Winners of first Tony Whitten Conservation Prize