Coating That Repels Oil
New materials clean themselves, elimi­nating the need for soap and water.

Source: “Designing superoleophobic surfaces”
Gareth H. McKinley, Robert E. Cohen, et al.
Science 318: 1618-1622

Results: Researchers at MIT and the Air Force Research Laboratory at Edwards Air Force Base in California have made novel materials that cause oil to bead up and form near-spherical droplets that easily roll or even bounce off surfaces. The researchers also analyzed the mechanisms behind the materials’ oil-repellent properties and developed design rules that could be useful for making similar materials in the future.

Why it matters: The researchers’ oil-repellent surfaces could make rubber hoses and engine seals more durable by preventing them from absorbing oil and swelling. Eventually, the detailed design rules could help scientists develop materials for other applications–such as transparent, self-cleaning displays, something cell-phone companies have been working on for years.

Methods: The air force researchers first developed new molecules containing high concentrations of fluorine atoms. When applied to a surface in a thin film, the molecules cause oil to bead up. The MIT researchers found a way to blend these molecules with commercial polymers and enhanced the liquid-­repelling properties of the blended material by spinning it into microscopic threads. These threads accumulate on a surface, creating a rough, air-trapping network that alters the contact angle between the material and oil, causing the oil to bead up even more than it would on a flat film.

Next Steps: The polymeric surfaces aren’t ideal: for one thing, they’re opaque. The researchers hope that the design rules they developed will allow other researchers to create super-oil-repellent materials that overcome current limitations.