Coating Made By Candlelight Repels Both Water And Oil

Using candle soot as a nanostructured template, researchers in Germany have developed a low-cost “superamphiphobic” coating that repels both water and oil (Science, DOI: 10.1126/science.1207115). A team led by Doris Vollmer of the Max Planck Institute for Polymer Research created the coating by first holding a glass slide above the flame of a paraffin candle. This step deposits a layer of carbon particles, roughly 30–40 nm in diameter, onto the slide. The researchers then used chemical vapor deposition to apply a silica shell, about 20 nm thick, to the carbon nanoparticles. They next heated the coating to 600 °C, which causes combustion of the carbon core and renders the coating transparent. In a final step they applied a layer of a semifluorinated silane via chemical vapor deposition. A combination of the nanoscale surface roughness and the fluorinated top layer makes the coating both hydrophobic and lipophobic. The coating can be applied to a variety of heat-resistant surfaces, including aluminum, copper, or stainless steel. And it retains its superamphiphobic properties during wear and abrasion so long as the thickness is greater than 1 μm.