December 11, 2023

Researchers have created a new type of ultra-thin material that may pave the way to a new era of waterproofing, affecting everything from cooking to transportation.

Hundreds of different technologies are affected by the way that water sticks to solid surfaces. So finding new, super-water-resistant coatings opens up a range of possibilities for designing more efficient, waterproof machinery in the future.

Liquid-like surfaces might fill this gap. These materials are made up of an ultra-thin liquid layer of water-resistant molecules, bonded to a solid surface of silicone underneath. This liquid layer acts like a layer of lubricant between the water droplets and the surface itself, causing the droplets to glide off the surface with very little friction.

Super waterproof nanomaterial
An artist’s depiction of the liquid-like layer of molecules repelling water droplets. The breakthrough will affect everything from cooking to transportation.
Ekaterina Osmekhina/Aalto University

In a new study, published in the journal Nature Chemistry on October 23, researchers from Aalto University in Finland found that these materials are equally water-resistant when the liquid-like molecules are present at a low concentration as they are at a high one.

‘Our work is the first time that anyone has gone directly to the nanometer-level to create molecularly heterogenous surfaces,’ doctoral researcher Sakari Lepikko, lead author of the study, said in a statement. ‘It was counterintuitive that even low coverage yielded exceptional slipperiness.”

At these low concentrations, the water becomes a film over the silicone’s surface. Previously, it was thought that this would increase friction between the water and the silicone surface. ‘We found that, instead, water flows freely between the molecules of the [liquid-like surface] at low [liquid-like molecule] coverage, sliding off the surface,” Lepikko said. “And when the [liquid-like molecule] coverage is high, the water stays on top of the [liquid-like surface] and slides off just as easily. It’s only in between these two states that water adheres to the [liquid-like molecules] and sticks to the surface.”

One of the main issues with these coatings is that they are very thin and so disperse easily after physical contact. However, Lepikko said that this new discovery could help increase the durability of these materials.

“Our counterintuitive mechanism is a new way to increase droplet mobility anywhere it’s needed,” Lepikko added. “Things like heat transfer in pipes, de-icing and anti-fogging are potential uses. It will also help with microfluidics, where tiny droplets need to be moved around smoothly, and with creating self-cleaning surfaces.”

The team hopes to continue testing the properties of this exceptionally waterproof material to inform its potential applications better in the future.

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