Simulation maps nano patterns

Microscopic machines promise to be useful in manufacturing materials molecule-by-molecule and eventually for applications like targeted drug delivery. But to construct a nanoscale machine you must figure out how to fabricate parts that are not much bigger than molecules.

Researchers from the University of Michigan have used a computer simulation to develop a method of chemically building nanoscale patterns on a surface. The patterns, which include neatly-positioned groups of wavy and straight lines, dots, boxes within boxes, and mixes of dots and lines, would be relatively inexpensive to produce and could form the basis for nanoscale machines.

To make the patterns, the researchers simulated the application of monolayers, or single-molecule layers of material, to an elastic substrate. Different materials self-assembled into different patterns. A partial-monolayer of oxygen on a monolayer of copper, for instance, forms regular, 10-nanometer stripes of oxygen alternating with bare copper. And a mix of copper and lead on copper forms ordered patterns of dots or stripes depending on the mix percentages. A nanometer is one millionth of a millimeter.

Key to the process is the surface chemistry, which governs how the atoms of the two layers interact on a uniform surface. The choice of materials determines the type, size and alignment of the pattern.

The researchers are working to expand the method to fabricate more complicated structures.

The process could be used practically in two to five years, according to the researchers. The work appeared in the February 11, 2004 issue of Nano Letters.