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Termites inspire hydrophobic materials
Termite wings are the latest inspiration from nature for scientists developing new materials that repel water.

Nanoscience researcher, Dr Gregory Watson of James Cook University in Townsville, and colleagues, report their study of water-repelling termite wings online in the journal ACSNano.

"Water droplets just spontaneously roll off them," says Watson.

Despite not being the best of fliers, winged termites generally fly in the rain.

"It's advantageous to fly in the rain because you've got a mobile canvas of droplets so it's harder for predators to see you," says Watson.

But given their large wing area to body mass ratio, how does a termite cope if it wants to avoid getting so soggy it drops out of the sky?

Watson and colleagues reasoned the structure of its wings must enable it to shed water droplets very easily.
Two-tiered system

The researchers took a close look at how termite wings repelled water and found an ingenious two-tiered "anti-wetting" system.

The wing surface is covered in micro-scale hydrophobic hairs and nano-scale star-shaped structures called "micrasters", says Watson.

He and colleagues studied the ability of both these structures to repel water.

They found the micrasters stop very small dew drops from sticking to the wing surface, while the hairs stop larger rain drops.

Watson says the hairs have a groove down their length, which his experiments found were essential to repelling water.

When the researchers filled up the groove with hydrophobic material, water was no longer repelled.

Watson says the groove is probably holding trapped air, which aids in repelling water from the surface.

"It also minimises adhesion too, because you have less contacting surface with the actual water droplet," he says.
Imitating nature

Watson and colleagues are now in the process of trying to replicate the termite wing surface.

He says understanding how termite wings repel water could have useful applications in designing self-cleaning surfaces like tiles and windows, as well as low-drag surfaces for ship hulls.

While many surfaces in nature have inspired scientists to create new materials, Watson says water-repelling termite wings are unique.

The termites need to be able to keep water off their wings without adding extra weight, which would make it even more difficult for them to fly than it is already, he says.

The grooved hair shaft and the star-like structures are perfect designs for minimising the amount of material necessary to making an anti-wetting surface, says Watson.

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