Natures wonders: rain drop protection (Introduction)

by David Turell , Tuesday, June 09, 2020, 22:38 (1626 days ago) @ David Turell

Rain drops are heavy and can be damaging to delicate surfaces like butterfly wings, which have protections=:

https://phys.org/news/2020-06-armor-butterfly-wings-heavy.html

"An analysis of high-speed raindrops hitting biological surfaces such as feathers, plant leaves and insect wings reveals how these highly water-repelling veneers reduce the water's impact.

"Micro-bumps and a nanoscale wax layer on fragile butterfly wings shatter and spread raindrops to minimize damage.

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"The research showed how microscale bumps, combined with a nanoscale layer of wax, shatter and spread these drops to protect fragile surfaces from physical damage and hypothermia risk.

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"Raindrops pose risks, Jung said, because their impact could damage fragile butterfly wings, for example.

"'[Getting hit with] raindrops is the most dangerous event for this kind of small animal," he said, noting the relative weight of a raindrop hitting a butterfly wing would be analogous to a bowling ball falling from the sky on a human.

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"In analyzing the film, they found that when a drop hits the surface, it ripples and spreads. A nanoscale wax layer repels the water, while larger microscale bumps on the surface creates holes in the spreading raindrop.

"'Consider the micro-bumps as needles," Jung said. If one dropped a balloon onto these needles, he said, "then this balloon would break into smaller pieces. So the same thing happens as the raindrop hits and spreads."

"This shattering action reduces the amount of time the drop is in contact with the surface, which limits momentum and lowers the impact force on a delicate wing or leaf. It also reduces heat transfer from a cold drop. This is important because the muscles of an insect wing, for example, need to be warm enough to fly.

"If they have a longer time in contact with the cold raindrop, they're going to lose a lot of heat and they cannot fly very easily," Jung said, making them vulnerable to predators, for example.

Repelling water as quickly as possible also is important because water is very heavy, making flight in insects and birds difficult and weighing down plant leaves.

Comment: The original design of butterfly wings had to include this protection mechanism or butterflies would not have survived. Not by chance