A New Coating Promises the End of Smudges

A team of researchers led by Doris Vollmer of the Max Plank Institute for Polymer Research (Mainz) has developed a simple way to create a specific surface roughness that repels oil as well as water, making the material "superamphiphobic".  Tests showed that droplets of various oils bounced off the surface, which can also be applied to metals such as aluminum, steel and copper.

Whereas earlier work at MIT required complex nanolithography, the team used a candle to deposit soot on a glass slide, resulting in a coating made up of 20% soot spheres that were 30 to 40 nanometers in diameter.  After applying a 25 nanometer protective silica shell, the soot was baked at 600C to take it transparent.   Work is underway to make the coating more durable.  The protective silica shell is currently applied using vapor deposition involving high temperatures - alternative methods using chemical solutions are being investigated.        

The approach is similar to the Lotus effect that relies on surface roughness to prevent water from 'wetting' the surface.  It is an example of using structure (rather than energy or materials) to make a surface that is self-cleaning.  The Max Planck team identified a way of creating the surface structure using relatively simple methods based on the physical properties of candle smoke and soot. 

Additional information can be found in Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating, publilshed in Science DOI: 10.1126/science.1207115, Published Online December 1 2011 

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