Novel coating repels water, oil and alcohol

WASHINGTON, June 24: Scientists, including one of Indian origin, have developed an omniphobic coating that can be applied on numerous surfaces to make them repel water, oil, and alcohol.
The chemical coating, developed by Anish Tuteja, an associate professor at the University of Michigan in the US, is clear, durable, can be applied to numerous surfaces and sheds just about any liquid.
Omniphobic coatings can reduce friction drag – resistance created by the movement of a hull through water – on ships, submarines and unmanned underwater vessels.
Compare friction drag to jogging through a swimming pool. Due to the water’s resistance, each stride is more difficult and requires more energy and effort.
“A significant percentage of a ship’s fuel consumption (up to 80 per cent at lower speeds and 40-50 per cent at higher speeds) goes toward maintaining its speed and overcoming friction drag,” said Ki-Han Kim, a programme officer at US Office of Naval Research (ONR), which sponsored the work.
“If we could find a way to drastically reduce friction drag, vessels would consume less fuel or battery power, and enjoy a greater range of operations,” said Kim.
While repellent coatings are not new, it is hard to create one that resists most liquids and is tough enough to stick to various surfaces for long periods of time.
“Researchers may take a very durable polymer matrix and a very repellent filler and mix them,” said Tuteja.
“But this doesn’t necessarily yield a durable, repellent coating. Different polymers and fillers have different miscibilities (the ability of two substances to mix together). Simply combining the most durable individual constituents doesn’t yield the most durable composite coating,” he said.
To engineer their innovative coating, researchers studied vast computer databases of known chemical substances. They then entered complex mathematical equations, based on each substance’s molecular properties, to predict how any two would behave when blended.
After analysing hundreds of combinations, researchers found the right mix.
The molecular marriage was a hit during laboratory tests. The rubber-like combo can be sprayed, brushed, dipped or spin-coated onto numerous surfaces, and it binds tightly.
The coating also can withstand scratching, denting and other hazards of daily use. The way the molecules separate makes the coating optically clear.
Besides reducing friction drag, the omniphobic coating could protect high-value equipment like sensors, radars and antennas from weather.
Tuteja’s team is conducting further tests on the omniphobic coating, but they plan to have it ready for small-scale military and civilian use within the next couple of years. (PTI)


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