Nanoscale 'Levitation' Discovery Could Lead to Better Nanomachines

[David Farber <dave () farber net>]

Begin forwarded message:

From: dewayne () warpspeed com (Dewayne Hendricks)
Date: January 9, 2009 6:49:53 PM EST
To: Dewayne-Net Technology List <xyzzy () warpspeed com>
Subject: [Dewayne-Net] Nanoscale 'Levitation' Discovery Could Lead to  
Better Nanomachines

Nanoscale 'Levitation' Discovery Could Lead to Better Nanomachines
<http://www.pbs.org/newshour/updates/science/jan-june09/nano_01-09.html>
        
By exploiting a quantum mechanical quirk, a team of researchers has  
discovered how to levitate a tiny object. The finding sounds magical,  
but it could have an important practical application -- helping  
scientists build better nanoscale machines.

"We could use this as a quantum mechanical lubricant," says Harvard  
physicist Federico Capasso, one of the authors of a paper published  
this week in the journal Nature.

The new research uses a force first described by the Dutch physicist  
Hendrik Casimir in 1948. Casimir predicted that due to quantum energy  
fluctuations, two metal plates placed very close together -- within  
nanometers of each other -- would attract one another.

Casimir's prediction was borne out in lab experiments, but until  
recently was interesting only to theoretical physicists. In recent  
years, however, as scientists have begun to work toward building  
nanoscale machines, they've realized that the Casimir force could  
cause practical problems -- making the tiny parts of those machines  
stick together and gumming up the works.

Capasso, in fact, first became interested in the problem when working  
at Bell Labs in the 1990s, building micro electromechanical systems  
(MEMS), the technology used in airbag sensors, among other things.

"We knew that if we kept scaling down the dimensions, from micrometer  
to nanometer, at some point these surfaces could stick to each other  
because of Casimir attraction," Capasso says.

Since the 1960s, though, researchers also realized that theoretically,  
if the air between the plates were replaced by the right material, the  
Casimir force would cause the materials to repel one another rather  
than attract. However, because the forces at work were so tiny, they  
were never able demonstrate the repulsive Casimir force in the lab.

[snip]
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