By Peter Weiss
Using an old tool in surprising new ways, scientists in California are making molecules race down the sloping sides of a minuscule silicon spike ordinarily reserved for poking at atoms. The novel role for the spike, which is the tip of an instrument known as an atomic-force microscope, or AFM, could lead to advances in DNA sequencing, nanofabrication of devices, and other technologies, the scientists say.
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About 10 micrometers long, an AFM’s tip protrudes from the end of a cantilever. Scientists usually drag it or tap it on a surface to discern an object’s topography down to the atomic level (SN: 2/18/06, p. 101: Available to subscribers at New View: Speedy microscope takes fuller look at the nanoworld). Now, H. Kumar Wickramasinghe and his colleagues at IBM Almaden Research Center in San Jose, Calif., have demonstrated that DNA molecules separate according to their lengths as they move along a spike’s wetted surface. Moreover, the scientists have used the spike’s point to lay down a nanoscale pattern of molecules.