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Foiling friction by jiggling a junction.

Friction can cause a hard-disk drive to crash or a microscopic motor to seize. One problem is that the lubricants in the minuscule gaps between surfaces of such devices settle into semi-solid layers that resist slipping motions.

A rhythmic resizing of those gaps will break up the layers and keep things gliding easily, according to computational and experimental results presented in the June 25 Journal of Physical Chemistry B.

"Typically we think of replacing the lubricant," says Uzi Landman of the Georgia Institute of Technology in Atlanta, who coauthored the computational report. "This is the first [study] that says: Keep the same lubricant and do something external."

Prior studies by Landman and his colleagues found that a waxy lubricant such as hexadecane would separate into four or five stable, motion-resistant layers, but only if the size of the gap filled by the lubricant remained fixed.

In new supercomputer simulations, Landman's team confirmed that if the gap becomes a little smaller or larger, molecules rearrange, disturbing the order and reducing friction. Rapidly varying the spacing by as little as 5 percent of a 2-nanometer, lubricant-filled gap caused "ultralow" friction, the team says.

In an accompanying experimental report, researchers at the Laboratory for Surface Science and Technology in Zurich and at the University of California, Santa Barbara describe sliding lubricated surfaces against each other while oscillating the top surface by less than 0.1 nm. Friction dropped markedly, they report--in one circumstance, tailing to less than a tenth of what it was with no oscillations.
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Title Annotation:lubricating electronic devices
Author:Weiss, Peter Ulrich
Publication:Science News
Article Type:Brief Article
Date:Jul 25, 1998
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