Superrepellent Surface

Organic solvents—especially fluorinated ones—are notoriously “sticky” when drizzled onto water-repellent surfaces. Rather than beading up and rolling off as water does, these low-surface-energy fluids spread out and hang around. Tingyi (Leo) Liu and Chang-Jin (CJ) Kim of the University of California, Los Angeles, have now succeeded in fabricating a surface that repels even the most stick-to-itive of solvents: perfluorohexane (Science 2014, DOI: 10.1126/science.1254787). The researchers hope their strategy will one day improve the efficiency of solvent-cooled electronics and the antifouling ability of biomedical implants. The researchers created their superrepellent silica surface by etching an array of microscale posts into a silicon substrate that eventually gets oxidized. The final surface architecture resembles regularly spaced nails hammered halfway into a board, where each nail head has an overhanging lip. It’s this lip that makes the surface impervious to low-surface-energy fluids such as perfluorohexane, Kim says. The overhang exerts a surface tension that compels the liquid to pull up rather than slide downward and wet the surface, he adds.