Shrugging Off Grime

Materials Science![Figure][1] Flat (top) and wrinkle-protected samples.CREDIT: EFIMENKO ET AL., ACS APPL. MATER. INTERFACES 1 , 10.1021/AM9000562 (2009) To prevent the accumulation of unwanted microorganisms, plants, and animals on surfaces exposed to a marine environment, coatings are applied to the submerged surface. One challenge in creating such a coating is that the critical length scales involved in organism attachment range from hundreds of nanometers to centimeters. Efimenko et al. have developed polymer coatings that possess a hierarchical wrinkled structure. They stretched and then cross-linked the surface of poly(dimethylsiloxane), after which they applied a fluorinated silane monolayer. On gentle relaxation of the stress, a rippled surface layer formed, wherein each wrinkle had smaller-scale wrinkles on top of it that themselves bore even smaller wrinkles, proceeding over five generations. In seawater tests, flat polymer films showed fouling after a few weeks, whereas the wrinkled polymers resisted barnacle accumulation over a period of 18 months. In tests on the adhesion of green algae zoospores, the wrinkled films performed less well, as the spores could nestle and be protected from shear flows and physical contacts within the wrinkles. However, a combination of topology and the right surface chemistry conferred improved resistance, pointing toward development of a nontoxic universal antifouling coating. ACS Appl. Mater. Interfaces 1 , 10.1021/am9000562 (2009). [1]: pending:yes