Engineers at the Massachusetts Institute of Technology have designed a material that can repel oil.
According to researchers, the materials could be used to help protect parts of airplanes that are vulnerable to damage from being soaked in fuel, like rubber gaskets and o-rings.
“These are vulnerable points in many aerospace applications,” said Robert Cohen, professor of chemical engineering. “It would be nice if you could spill gasoline on a fabric or a gasket or other surface and find that instead of spreading, it just rolled off.”
Creating an oil-repelling, or “oleophobic,” material has been challenging for scientists, as there are no examples in nature.
“Nature has developed a lot of methods for waterproofing, but not so much oil-proofing,” said Gareth McKinley, a professor of mechanical engineering and a member of the research team. “The conventional wisdom was that it couldn’t be done on a large scale without very special lithographic processes.”
The tendency of oils to spread out over surfaces is due to their very low surface tension (a measure of the attraction between molecules of the same substance). Water, on the other hand, has a very high surface tension and tends to form droplets. This explains why water will roll off the feathers of a duck, but a duck coated in oil must be washed with soap to remove it.
The MIT team overcame the surface-tension problem by designing a material composed of specially prepared microfibers that cushion droplets of liquid, allowing them to sit, intact, just above the material’s surface. When oil lands on the material, which resembles a thin fabric or tissue paper, it rest atop the fibers and pockets of air trapped between the fibers.
The microfibers are a blend of a specially synthesized molecule called fluoroPOSS, which has an extremely low surface energy, and a common polymer. They can be readily deposited onto many types of surfaces, including metal, glass, plastic and even biological surfaces such as plant leaves, using a process known as electrospinning.
The researchers have already created a fabric that can separate water and jet fuel. The Air Force, which funded the research and developed the fluoroPOSS molecules, is interested in using the new materials to protect airplanes from jet fuel.