Molecular tools for nanomanufacturing.

Although most people find unfathomable the concept of assembly lines that fit into a space no wider than a human hair, a small group of California scientists thinks molecular manufacturing could some day revolutionize the factory floor.

Toward this goal, two of these researchers have developed computer software to design and test molecular gears and bearings. These simulated components represent the first steps toward building machines that assemble parts atom by atom, molecule by molecule, says Ralph Merkle of the Xerox Palo Alto (Calif.) Research Center. He described these components last week in Palo Alto at the First General Conference on Nanotechnology.

Since the first nanotechnology conference in 1989 (SN: 11/4/89, p.295), researchers in many fields have demonstrated or observed ways to manipulate atoms and molecules and to make nanoscale modifications in their materials. But those advances have not yet captured the true spirit of nanotechnology or, in particular, of molecular manufacturing, says K. Eric Drexler, who heads the Palo Alto-based Foresight Institute.

"In molecular manufacturing, the making of the material and the making of the component [are] one and the same," says Drexler, who helped develop the simulated bearings. He has proposed that modified atomic force microscopes will represent the first-generation molecular machines. Fitted with tips that grab and move particular atoms or molecules, these microscopes will build invisible robotic arms and molecular assemblers that will eventually man nanoscale factories.

So far, Drexler and Merkle have succeeded in simulating just a few components -- a bearing and a speed reduction, or planetary, gear -- of the thousands needed for these devices.

"We can't do it now, but it's really important to assess how close we are to building such a structure," comments Michael Kelly, a materials scientist at Stanford University.

With the simulations, "we've been increasing our confidence that molecular-level structures are feasible," says Merkle. For example, their results indicate that the bearing's two-layer carbon rings, whose atoms arrange like those in a diamond, will bend to form a hoop without losing that diamond-like arrangement. They also determined the bearing's ideal ring sizes.