Normally, to make water roll off surfaces we spray them with toxic chemicals, like Rust-Oleum’s NeverWet, which contains acetone (nail polish remover), liquid petroleum gas, and a few additional “magic” ingredients.
But some surfaces aren’t safe for chemical spray — like things we want to eat off of or are near children. Instead of using chemicals, we can design surfaces that naturally repel water. Because of their texture, these surfaces completely shed water instead of absorbing it.
Researchers from MIT designed a new, even better textured surface that stays completely dry. The paper was just published in the journal Nature.
Without the texture, the hydrophobic surface acts like a lotus leaf. It traps air on the surface, which provides a buffer between the actual surface and the water droplet. Although a droplet of water will roll right off, it will still flatten completely against the surface (allowing time for the surface to absorb some of the water) before retracting into a ball and bouncing off.
Scientists realised if they could make the droplets break up into smaller drops instead of flattening into a pancake, the water would be in contact with the surface for a much shorter period of time, meaning there’s less of chance of the water absorbing into the surface.
They did this by adding microtextures to an already hydrophobic surface. These microtextures redistribute the water and break up the flattened pancake of liquid so it can’t form back into a drop.
Here’s a comparison of the two surfaces, with and without microtextures:
One application, the researchers say, is in aircraft. It works so quickly that even in super-cold environments the water doesn’t stick long enough to freeze. By making the surface of the engines repel water before it ices up, they could potentially reduce the amount of frost that builds up.
Here’s a quick Nature Video on the development:
They went looking in nature and realised that a very similar pattern is used on butterfly wings and the leaves of the nasturtium plant, which also have ridges to break up droplets.
This is just one example of bio-mimicry, a growing field of engineering and other sciences in which researchers are looking to nature for inspiration.
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