United States. It can repel water, oil, alcohol and even peanut butter. And it could save the U.S. Navy millions of dollars in vessel fuel costs, reduce the amount of energy vessels consume, and improve operational efficiency.
The Office of Naval Research (ONR) is sponsoring the work of Dr. Anish Tuteja, an associate professor of materials science and engineering at the University of Michigan, to develop a new type of "omnipobic" coating. This chemical coating is transparent, durable, can be applied to numerous surfaces and throws up almost any liquid.
The navy's interest is how omnipobic coatings can reduce frictional drag, resistance created by the movement of a hull through water on ships, submarines and unmanned underwater vessels.
Compare the friction resistance for running through a pool. Due to the resistance of the water, each step is more difficult and requires more energy and effort.
"A significant percentage of a ship's fuel consumption — up to 80 percent at lower speeds and 40-50 percent at higher speeds — goes toward maintaining its speed and overcoming friction drag," said Dr. Ki-Han Kim, an ONR program officer. Department of Arms and Sea Warfare. "If we could find a way to drastically reduce friction resistance, ships would consume less fuel or battery power and enjoy a greater range of operations."
The omnipobic coating of the researcher Tuteja could be a solution. Imagine two boats sailing at the same speed, one dealing with friction resistance and the other covered by a layer that makes the water turn and slide easily down the hull. In theory, the coated container gobbles up less fuel because it doesn't have to fight as much water resistance while maintaining speed.
While repellent coatings aren't new, it's hard to create one that resists most liquids and is sturdy enough to stick to various surfaces for long periods of time. Take a tray lined with Teflon, for example. The water will round off and roll out of the tray, while the cooking oil will spread everywhere.
"Researchers can take a very durable polymer matrix and a very repellent filler and mix them up," Tuteja said. "But this doesn't necessarily produce a repellent and durable coating. Different polymers and fillers have different miscibilities [the ability of two substances to mix with each other]. Simply combining the most durable individual components does not produce the most durable composite coating."
To design their innovative coating, Tuteja and his research team studied vast databases of known chemicals. They then entered complex mathematical equations, based on the molecular properties of each substance, to predict how two would behave when mixed. After analyzing hundreds of combinations, the researchers found the right combination.
The molecular marriage was a success during laboratory tests. The rubber-like combo can be sprayed, brushed, bathed or centrifuged on numerous surfaces, and is tightly bonded. The coating can also withstand scratches, dents, and other everyday hazards. And the way the molecules separate makes the coating optically transparent.
In addition to reducing friction drag, Tuteja envisions other Navy uses for omnipobic coating, which includes the protection of high-value equipment such as sensors, radars and weather antennas.
In addition to omnipobic coatings to decrease friction resistance, ONR is sponsoring other types of coating research to prevent corrosion on both ships and aircraft and fight biofouling (the accumulation of barnacles on hulls). Similar coatings can also prevent ice from forming on ships operating in cold regions, or make ice removal much easier than conventional methods such as scraping.
Tuteja's team is conducting further tests on the omnipobic coating, but they plan to have it ready for small-scale military and civilian use in the coming years.
Source: Office of Naval Research.
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