Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating

In the Stick of It If a coating makes a surface nonstick, how do you stick the coating to the surface in the first place? For many nonstick coatings, this involves procedures to ensure good adhesion to the underlying surface though the use of surface roughening or intermediary layers. Deng et al. (p. 67, published online 1 December; see the cover) found a very simple route using little more than candle soot as a temporary sublayer that is coated with a silica shell and subsequently removed via calcination. Once top-coated with a semifluorinated silane, the resulting material possessed a low surface energy for water and also repelled oils, alchohols, and alkanes. While the coating could be damaged through mechanical wear, the remaining material continued to show superhydrophobic and superoleophobic behavior. Coatings that are highly resistant to water and to hydrocarbons can be made starting from candle soot. Coating is an essential step in adjusting the surface properties of materials. Superhydrophobic coatings with contact angles greater than 150° and roll-off angles below 10° for water have been developed, based on low-energy surfaces and roughness on the nano- and micrometer scales. However, these surfaces are still wetted by organic liquids such as surfactant-based solutions, alcohols, or alkanes. Coatings that are simultaneously superhydrophobic and superoleophobic are rare. We designed an easily fabricated, transparent, and oil-rebounding superamphiphobic coating. A porous deposit of candle soot was coated with a 25-nanometer-thick silica shell. The black coating became transparent after calcination at 600°C. After silanization, the coating was superamphiphobic and remained so even after its top layer was damaged by sand impingement.