The researchers, from the University of California, Davis, and Wayne State University, Detroit, drew lines of DNA molecules as small as 15 nm across and 150 nm long. "We believe that these are the smallest nanostructures of DNA yet made," said Gang-yu Liu, a chemist at the University of California, Davis.
To make the patterns, Liu and the team coated a gold film with thiol molecules, which attach to the gold surface via a sulphur atom at one end. They scraped away selected thiols with an atomic-force microscope probe and then recoated the exposed gold with oligonucleotides - short pieces of DNA with thiols attached at one end.
The researchers, who reported their work in Nano Letters, say that the attached DNA molecules were both accessible and chemically active. They also claim that the technique could make structures as small as 2 by 4 nm.