US Navy conducts research on super lyophobic coatings to reduce energy costs

To make ships and submarines more flexible, the US Naval Research Office (ONR) funded a “lyophobic” coating study. It will not only have the ability to waterproof but also block other substances like oil, alcohol and even peanut butter. University of Michigan graduate assistant Mathew Boban pours cetane oil onto a glass slide coated with a polysaccharide film. Petroleum-based high viscosity oils can easily slip off the glass. The study aims to reduce the frictional resistance on ships, submarines and unmanned underwater ships (resistance caused by the hull moving in the water).

The coating repels water, oil, alcohol and even peanut butter. It saves the US Navy millions of dollars in ship fuel costs while reducing vessel energy consumption and improving vessel efficiency.


The Office of Naval Research (ONR) is funding Dr. Anish Tuteja, associate professor of materials science and engineering at the University of Michigan, for research on new "multi-functional" coatings. This chemical coating is clean, durable and can be applied to many surfaces and rejects almost all liquids.


Of particular interest to the Navy is how the paint reduces the frictional drag generated by the hull movement during underwater navigation of ships, submarines and unmanned underwater vehicles.


We can compare the frictional resistance to jogging in the pool. Due to the resistance of the water, each step forward is more difficult and requires more energy and physical strength.


“A significant proportion of the ship's fuel consumption (up to 80% at low speeds and 40-50% at high speeds) will be used to maintain speed and overcome frictional resistance,” said Ki-Oi, Department of Weapons and Weapons Department, ONR Dr. Han Kim said. “If we can find a way to significantly reduce the frictional resistance, the vessel will consume less fuel or battery energy and can work on a larger scale.”


Dr. Tuteja's super lyophobic coating may be a solution. Imagine that two ships sail at the same speed—one that needs to overcome frictional resistance and another that has a coating on the surface of the hull that makes it easy for water to form water droplets and slip away from the hull. In theory, paint coated hulls can significantly reduce fuel consumption. Because it does not need to resist so much water resistance while maintaining speed.


Although waterproof coatings are not new products, it is currently difficult to make coatings that repel most liquids and are tough enough to stick to a variety of surfaces for extended periods of time. For example, use a pan coated with Teflon. The water will be pearled and rolled down, and the cooking oil will spread everywhere.


“Researchers may use very durable polymer matrices and very repulsive fillers and mix them together,” Dr. Tuteja said. “But this does not necessarily result in a durable waterproof coating. Different polymers and fillers have different miscibility (the ability to mix the two together). Just mechanically blending the most durable individual ingredients together, ultimately It does not form the most durable composite coating.


To design their innovative coatings, Dr. Tuteja and his research team have studied a large number of computer databases of known chemicals. They then enter complex mathematical equations based on the molecular properties of each substance to predict the behavior of any two objects when they are mixed. After analyzing hundreds of combinations, the researchers finally found the right combination.


The intermolecular marriage was hit in laboratory tests. A rubber-like combination can be sprayed, brushed, dipped or spin coated onto multiple surfaces and tightly bonded. The coating also withstands scratches, dents and other everyday hazards. The way the molecules are separated makes the coating optically visible.


In addition to reducing frictional resistance, Dr. Tuteja also considered the Navy's other needs for multi-functional coatings – including protecting expensive equipment such as sensors, radars and antennas from the weather.


In addition to super-non-viscous coatings that reduce frictional resistance, ONR also funds other types of coating research to prevent corrosion of ships and aircraft and to prevent biofouling (the formation of barnacles on the hull). A similar coating also prevents the ship from freezing when it travels in cold areas, perhaps more easily than conventional methods such as scraping.


Dr. Tuteja's team is conducting further testing on super-lyophobic coatings, but they plan to prepare for small-scale military and civilian applications in the next few years.


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