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Even the nicest water-resistant materials, from synthetics to waxed canvas, can be ruined by certain liquids?that soak right in while rain and coffee?roll off. Scientists at the University of Michigan have created a surface that repels not just everyday fluids but exotic and dangerous ones.
The "superomniphobic" material works by reducing the amount of surface that's exposed to any given liquid it encounters, meaning that that liquid's surface tension (which keeps its together in a droplet or stream) remains intact.
A series of short videos accompanies the?article in the Journal of the?American Chemical Society, demonstrating the various ways in which liquid refuses to interact with the superomniphobic surface. Droplets bounce and roll across the surface, streams richochet off, and hydrochloric acid has no corrosive effect. Even "non-Newtonian" fluids like blood and shampoo, famously difficult to stop from soaking and staining, have been tamed.
Anish Tuteja, lead researcher on the project, and his colleagues have been working on similar omniphobic surfaces?for over five years, but this one is the best by far, he told NBC News.
"On the first generations, the droplets were leaving something behind," he said ? a problem around hazardous materials that could cause trouble later by evaporating or falling off. Not any more.
Yet it can't be totally impermeable. "It's a very, very porous coating ? porous to anything that's gas-based, but not to anything liquid." That means ordinary air and water vapor can pass through ? helpful when you don't want your clothing to stifle you.
The researchers achieved this balance by allowing much of the coating to be air ? in fact, between 95 and 98 percent of its?surface area. Up close, it appears like a loosely woven mat. Look closer, and the fibers begin to appear spiky.
When a droplet of water comes into contact with the surface, it's basically balanced on the tips of those spikes, with vast spaces of air in between. They don't overcome?the liquid's?surface tension, meaning the droplet keeps its shape and bounces or rolls along.
The spaces are big enough to allow air to breathe through, but small enough that neither oil, water, or acid will have enough contact to soak through. It's like a tennis ball on a net ? the net is light enough to see through, but the ball will bounce right off. If the spaces were much bigger, the ball would go through, and if they were much smaller, you wouldn't be able to see.
The work's not done, Tuteja said. Although he has "three or four" parties?interested in this type of material, not least of which is the military (which partially funded the research), there are still improvements to be made.?
"We definitely need to improve the mechanical durability, increasing the number of washing cycles, and so on," he said. A rather pedestrian concern for a leader in the field, but it's what needs to be done to get the superomniphobic material out of the lab and onto our coats and shoes.
Devin Coldewey is a contributing writer for NBCNews Digital. His personal website is?coldewey.cc.
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