For the first time, microscopic robots made from DNA molecules can walk, follow instructions and work together to assemble simple products on an atomic-scale assembly line, mimicking the machinery of living cells, two independent research teams announced Wednesday. These experimental devices, described in the journal Nature, are advances in DNA nanotechnology, in which bioengineers are using the molecules of the genetic code as nuts, bolts, girders and other building materials, on a scale measured in billionths of a meter. The effort, which combines synthetic chemistry, enzymology, structural nanotechnology and computer science, takes advantage of the unique physical properties of DNA...