Science & Technology

Scientists Have Finally Made an Everything-Repellent Coating

You might remember seeing videos of amazing products that, with just a spray, could make any object repel any liquid. Unfortunately, those products are often more hype than reality: they rub off quickly, they leave a frosty haze on every surface, and they make the objects feel rough and sticky. Well, we have good news. Materials science researchers at the University of Michigan have taken a unique approach to making an industrial-strength "omniphobic" coating and it looks like they've pulled it off.

Mathew Boban, Graduate Student Research Assistant, Materials Science and Engineering, pours hexadecane oil onto a glass slide with a superomniphobic coating. The petroleum based, highly viscous lubricant slides easily off the slide, opening up applications like self-cleaning windows, ink jet printers and microfluidic devices.

It's Rubber and You're Glue

Generally, scientists hoping to make a new material will take two or more existing materials that have the qualities they want, mix them together, then test the final product to see if it does what they want. The problem with that is even if the materials you're using have the right properties, they don't necessarily mix together well — and when substances mix badly, that leads to less-than-perfect color and durability.

Instead, University of Michigan associate professor of materials science and engineering Anish Tuteja and his team built this substance from the ground up. They mapped out the fundamental properties of a huge variety of different substances, which helped them mathematically predict how any two will behave together. One of those properties was what they called "partial miscibility," which is a measure of how perfectly the two substances will mix together. Better mixing means more durability, even if the individual substances aren't particularly durable themselves.

Their goal was to make a substance that was optically clear so it would be invisible on any surface; smooth enough to repel not only water, but also oils and alcohols; and versatile enough to stick to a wide variety of surfaces. The smoothness was especially important.

"You can repel water with a rough surface that creates tiny pockets of air between the water and the surface, but those surfaces don't always repel oils or alcohols because of their lower surface tension," Tuteja said in a press release. "We needed a very smooth surface that interacts as little as possible with a variety of liquids, and we also needed ingredients that mix together very well, because too much phase separation between ingredients will scatter light."

Like Water Off FPU's Back

In the end, they landed on the perfect combo: fluorinated polyurethane and a special fluid-repellent molecule called F-POSS. That substance is perfectly clear and can be sprayed, brushed, dipped, or spin-coated onto a wide variety of surfaces. Even if the object gets scratched or scuffed, the coating will keep on working to repel water-, oil-, and alcohol-based substances — even peanut butter and jelly. You can see a demonstration of how their coating works to repel different fluids compared to other coatings below.

So when can you get your hands on some? The team is working on getting the coating to market, but first they have to make absolutely certain that it's safe, durable, and cost-effective. They may be able to tweak the recipe just right to make this a product you see on hardware store shelves in the coming years.

Written by Ashley Hamer May 8, 2018

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