Have you ever wondered why water droplets stick to some surfaces but slide off others? A team of researchers has made the most water-resistant surface in the world that could redefine our understanding of this everyday phenomenon. This breakthrough not only opens up avenues for studying droplet behavior at the molecular level but also promises transformative applications, from our household plumbing to the cars we drive.
Water constantly engages with solid surfaces. From cooking to transportation, many things are affected by the way water adheres to or repels off surfaces. Delving into the molecular dynamics of these minuscule water droplets empowers scientists and engineers to enhance a multitude of household and industrial technologies.
Liquid-like surfaces are an innovative type of surfaces that exhibit exceptional resistance to droplets, offering numerous technical advantages compared to other methods. They have mobile molecular layers anchored to the substrate, creating a liquid-like quality that works as a natural lubricant between droplets and the hard surface.
Using a custom-designed reactor, a research team from Aalto University created a liquid-like layer of self-assembled monolayers (SAMs) on a silicon surface. “It’s the first time that anyone has gone directly to the nanometer-level to create molecularly heterogeneous surfaces,” study author Sakari Lepikko said in a news release.
By tweaking conditions in their custom reactor, like the water content, the team could control the SAM coverage on silicon. “The results showed more slipperiness when SAM coverage was low or high, which are also the situations when the surface is most homogeneous,” study author Robin Ras said in a news release.
When the coverage was low, water formed a surface film, a phenomenon previously believed to elevate friction levels. “We found that, instead, water flows freely between the molecules of the SAM at low SAM coverage, sliding off the surface. And when the SAM coverage is high, the water stays on top of the SAM and slides off,” Ras said.
A new barrier against water
The novel method demonstrated remarkable effectiveness, resulting in what the researchers describe as the world’s most slippery liquid surface. They believe it holds significant promise for applications requiring droplet-repellent surfaces, spanning a wide range of scenarios from everyday life to industrial solutions.
“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. Our counterintuitive mechanism is a new way to increase droplet mobility,” Lepikko said in a news release.
However, the journey is far from over. Up next, the researchers will continue working with their monolater setup and improve the layer itself. The main problem with the SAM coating is that it’s very thin so it disperses after physical contact.
“But studying them gives us fundamental scientific knowledge which we can use to create durable practical applications,” Lepikko said.
The study was published in the journal Nature Reviews Chemistry.