Insects Showcase Unexpected Ways to Make Water-Repellent Surfaces
Published:20 Jul.2020 Source:Science
The intersection between water, air, and insects’ intricately decorated surfaces turn out to be the key to explain why droplets bounce so quickly off of them.
For the last several decades, the lotus leaf has been the model for slippery, water-repellent surfaces. The leaf is covered in micro-scale pillars that are decorated with tiny structures, like a microscopic forest, explains Penn State materials scientist Tak-Sing Wong. The density of the “trees” is relatively low, creating a thin layer of air between the lotus leaf surface and the canopy. When a water droplet lands on the lotus leaf, it sits on the pocket of air and becomes very mobile, like a puck on an air hockey surface.
It stands to reason that other water-repellent organisms might also use this strategy, but to the surprise of Wong and his colleagues, that’s not what they found in their latest investigation mosquito eyes, cicada wings, and springtail bodies, described in Science Advances today (July 17). “In the tree analogy, there is no tree, just grassland,” explains Wong. Instead of a sparse forest, these insects’ surfaces are covered in dense, nanoscale spikes, like blades of grass.