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Nanoscale Wear

One of the major problems for micromachines, much less nanomachines, is wear. The phenomenon of stiction combines the two worst aspects of surface-to-surface interaction — a high coefficient of friction and a locally-generated high applied force — to cause enormous problems. At the very smallest scale, once we gain complete control over atomic configuration, superlubricity kicks in. But at intermediate scales, wear scales the wrong way: for fixed forces and speeds, wear grows as a proportion of part size as size scales down.

Vibratory Parts Feeder

Vibratory Parts Feeder

One way of reducing friction at the macroscale is vibration, as in this vibratory parts feeder. Now nanotechnologists at IBM have harnessed vibration to reduce wear at the nanoscale:

In their paper, published in the September issue of Nature Nanotechnology, IBM scientists solve this challenge by “demonstrating the effective elimination of wear on a tip sliding on a polymer surface over a distance of 750 meters by modulating the force acting on the tip-sample contact.” By applying an AC voltage between the cantilever—the mechanical arms on which the tips are attached and over which they are controlled—and the sample surface, the cantilever can be excited at high frequencies of one Megahertz. The cantilever bends and the tip vibrates with an almost imperceptible estimated amplitude of one nanometer.

This is over a thousand times faster vibrations than in macroscale machines, but then that’s what one would expect…

[“Dynamic Superlubricity and the Elimination of Wear on the Nanoscale” by M.A. Lantz, D. Wiesmann, and B. Gotsmann,  Nature Nanotechnology 4:9 (September 2009)]

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