Most repellent surface ever has been created by researchers

Researchers have managed to create a super water-repellent surface – a breakthrough that could offer potential new applications in plumbing, optics and the automotive and maritime sectors.

Challenging current understandings of the interaction between solid surfaces and water, the research was published in Nature Chemistry. It details how better understanding the molecular dynamics of water droplets on surfaces can provide insight into enhancing various technologies.

As part of the study, the researchers introduced a new type of water-repellent surface known as liquid-like surfaces. These surfaces consist of a unique structure of molecular layers that are highly mobile while having a strong chemical bond. This provides a lubricant-like layer between water droplets and the solid surface.

Like water off a duck's back

Leading this research, a team used a specially designed reactor to create a liquid-like layer of self-assembled monolayers (SAMs) on a silicon surface.

"Our work is the first time that anyone has gone directly to the nanometer level to create molecularly heterogeneous surfaces," explained the study's lead author, doctoral researcher Sakari Lepikko.

By controlling parameters such as temperature and water content in the reactor, Lepikko said the scientists could precisely control the coverage of the silicon surface by the SAM layer.

The results demonstrated that the surface had increased slipperiness when the SAM coverage was either low or high, corresponding to situations where the surface was more uniform in its composition.

Surprisingly, even low coverage of SAMs resulted in high levels of slipperiness, challenging the conventional belief that a film of water over a surface would increase friction. And so, the research revealed that water flows freely between SAM molecules at low coverage, allowing it to slide off the surface.

When the SAM coverage is high, water remains on top of the SAM layer and can still slide off easily. Only in the intermediate state does water adhere to the SAMs and stick to the surface.

The world's slipperiest surface

The new technique has achieved an impressive milestone by creating the world's slipperiest liquid surface – a discovery that's poised to have broad applications wherever water-repellent surfaces are needed.

The potential uses include heat transfer in pipes, de-icing, anti-fogging, microfluidics and the development of self-cleaning surfaces.

"Our counterintuitive mechanism is a new way to increase droplet mobility wherever it's needed," added Lepikko.

Although SAM coatings are extremely thin and can disperse easily upon physical contact, it's thought that the scientific knowledge gained from this work can be harnessed to create more durable and practical applications in the future.