Armor on butterfly wings protects against heavy rain, Says Research

The recent research on “How a Raindrop Gets Shattered on Biological Surfaces,” published on June 8 in the Proceedings of the National Academy of Sciences remarked that, the analysis of high-speed raindrops hitting biological surfaces such as feathers, plant leaves and insect wings, plant leaves 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.

However, Many biological surfaces of animals and plants (For example, bird feathers, insect wings, plant leaves, etc.) are superhydrophobic with rough surfaces at different length scales. Researchers says that getting hit with raindrops is the most dangerous event for such type of small animal, 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, The researchers stated.

In the concerned study, the researchers have acquired samples of leaves, feathers and insects. The latter were collected from the Cornell University Insect Collection, with the help of co-author Jason Dombroskie, collection manager and director of the Insect Diagnostic Lab. And the researchers placed the samples on a table and released water drops from heights of about two meters, while recording the impact at a few thousand frames per second with a high-speed camera.

Meanwhile, senior author named Sunghwan Sunny Jung, associate professor of biological and environmental engineering in the College of Agriculture and Life Sciences says that, “This is the first study to understand how high-speed raindrops impact these natural hydrophobic surfaces,”. While the lead author is Seungho Kim, a postdoctoral researcher in Jung’s lab. In analyzing the film, researchers 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 remarked.

Following the research, It highlighted 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. There already exists a large market for products that use examples from nature – known as biomimicry – in their design: self-cleaning water-resistant sprays for clothes and shoes, and de-icing coatings on airplane wings. Findings from this study could lead to more such products in the prospect, The finding suggests.

However, Previous studies have focused at water hitting insects and plants at low impacts and have noted the liquid’s cleaning properties. But in nature, raindrops can fall at rates of up to 10 meters per second, so this latest research have examined how raindrops falling at high speeds interact with super-hydrophobic natural surfaces. Raindrops pose risks, Sunny Jung attributed, because their impact could damage fragile butterfly wings, for instance.

The Senior author, If one dropped a balloon onto these needles, “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, he asserted.

Despite all of this, The study was funded by the National Science Foundation and the United State Department of Agriculture. “If they have a longer time in contact with the cold raindrop, they are going to lose a lot of heat and they cannot fly very easily,”. For instance, Making them vulnerable to predators. Repelling water as quickly as possible also is significant because water is very heavy, making flight in insects and birds difficult and weighing down plant leaves, “By having these two-tiered structures”, these organisms can have a super hydrophobic surface, Senior author Sunghwan Sunny Jung highlighted.

(Author: Trilok Singh is with CEO here).

Note: Content may be edited for length and style.

Journal Reference:

1. Seungho Kim, Zixuan Wu, Ehsan Esmaili, Jason J. Dombroskie, Sunghwan Jung. How a raindrop gets shattered on biological surfaces. Proceedings of the National Academy of Sciences, 2020; 202002924 DOI: 10.1073/pnas.2002924117