J. Am. Chem. Soc. 133, 11868–11871 (2011)

The design of DNA molecules that readily fold into arbitrary shapes — DNA origami — holds promise for the bottom-up fabrication of nanoscale devices, both through DNA-directed self-assembly and nanopatterning processes. The patterning of inorganic substrates with DNA templates usually requires the deposition of intermediate mask layers as these molecules are sensitive to common dry etchants. Haitao Liu and colleagues now show that SiO2 surfaces can be patterned using self-assembled DNA alone in a vapour-phase etching process. Owing to a difference in affinity towards H2O, deposited DNA molecules modify the local water concentration on SiO2 surfaces. The etching rate of these surfaces with HF gas, in turn, increases in the presence of adsorbed water. The researchers exploit this dependence to modulate the etching rate in close vicinity of the DNA molecules. Depending on the relative humidity of the environment, this process allows them to fabricate trench or ridge patterns with feature sizes below 20 nm. On further refinement the method could reach molecular-scale resolution and enable the patterning of additional layers underneath the SiO2, the researchers suggest.