One major hurdle that scientists faced with creating moving and functional micromechanical devices was the inability to properly lube the system, which inevitably lead to a mechanical breakdown.
Nature is reporting that the dilemma may have been solved:
Now researchers say they have found a fix. By saturating devices with argon gas containing a small amount of alcohol vapour, they can make microscopic machines run at least 100,000 times longer without failing.
“We’ve found a chemical that really works,” says Seong Kim of Pennsylvania State University in University Park, who has been working in a collaboration with Michael Dugger of Sandia National Laboratories in Albuquerque, New Mexico. He reported their latest results on 6 April at a meeting of the American Chemical Society in New Orleans, Louisiana.
Micromachined silicon surfaces can easily stick together through capillary forces, chemical bonding and other interactions. To prevent lock-up, engineers spray MEMS with fluorine-bearing silane to create a single-layer coating. But any contact between machine parts can easily rub this thin layer off and cause parts to stick.
Such devices could theoretically have moving parts if they could be immersed in lubricant, as there would then be a constant supply of slippery material to keep parts sliding.
But liquid lubricants will not work with MEMS. The components are so tiny that ordinary oils would create a lot of drag, Kim says, rather like asking a person to swim in a pool of honey or waltz in a swamp.
Kim thought that a gas might accomplish continuous lubrication without imposing a lot of drag. To investigate this, his research team pumped 1-pentanol vapour around a MEMS containing a part that slid back and forth over another surface. The gas seemed to eliminate wear entirely, allowing the machine to move for extended times with little resistance.
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Image info: SEM image of an insect (spider mite) on a polysilicon MEMS gear-train.