Now, an ”antisocial” material that can repel both water and oil

November 11th, 2008 - 5:55 pm ICT by ANI  

London, Nov 11 (ANI): It won”t be long when one could have easy-to-clean surfaces that can repel almost all liquids, even oily fluids long noted for their ability to foul water-repellent surfaces - thanks to US chemists who have developed “omniphobic” material that repels both water and oil.
And scientists at the Massachusetts Institute of Technology, even coined a new word to describe their creation - “omniphobic” - meaning it hates everything. The material has a surface texture that can force away watery and oily liquids into tight droplets.
The material’’s surface consists of 300-nanometer-tall “toadstools” with broad silicon dioxide caps and narrow silicon stems.
All the liquids have a surface tension that tries to pull a drop into a perfect sphere, but the strength of that tension varies between liquids.
Water has a very high surface tension, which enables it to form near-spherical drops when placed on a surface. On the other hand, oils such as pentane have a low surface tension, making them sag under gravity and tend to form a flat pool rather than a spherical droplet
Cohen said that the shape of the omniphobic toadstools enables the weak surface tension to hold a droplet together, allowing liquids like pentane to form a sphere without collapsing.
“If you stand on top of one of these [toadstools] and start walking towards the edge, you”ll pass through all angles and eventually you”ll be standing upside down,” New Scientist quoted him as saying.
When it comes to oily liquids, they form a meniscus between adjacent toadstools, and leave a layer of air beneath the toadstools” caps.
While, the toadstools are slightly omniphobic on their own, but scientists still added a surface coating to enhance the effect.
Thus they used a chemical called fluorodecyl POSS, which is usually used to make surfaces more hydrophobic.
On coating the surface, it was found that the material repels even oily liquids with low surface tension, such as pentane.
“Pentane is probably the lowest energy liquid you can have at atmospheric pressure, and we were able to get drops of that just rolling around on our surface,” said Cohen.
David Quere at the Higher School of Industrial Physics and Chemistry of the City of Paris said that it will be very easy to find real-world applications for the material.
He said that a large number of concrete and glass companies have been interested in similar surfaces to improve their materials.
“But when you put this texture on the surface of a solid it is very easily destroyed - [the toadstools] are quite fragile,” he said.
And, if the materials could become more robust, they could be used in making easy-to-clean surfaces that are difficult to soil with either watery or oily dirt. (ANI)

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