
Metamaterials reverse casimir force
Date: Saturday, August 04, 2007 @ 16:05:10 UTC Topic: Science
This is an incredible development that I'm sure will have far reaching repercussions! Perhaps this will lead to practical ZPE/Vacuum engineering? I can only hope.
'The normally attractive Casimir force between two surfaces can be made repulsive if a "perfect" lens with a negative index of refraction is sandwiched between the surfaces, according to calculations done by physicists in the UK.
Ulf Leonhardt and Thomas Philbin of the University of St Andrews reckon
that the repulsive force may even be strong enough to levitate a tiny
mirror. The repulsive effect -- which has yet to be observed
experimentally -- could also help minimize the friction in
micrometre-sized machines caused by the Casimir force (New Journal of
Physics to be published).
The mysterious attraction between two
neutral, conducting surfaces in a vacuum was first described in 1948 by
Henrik Casimir and cannot be explained by classical physics. Instead it
is a purely quantum effect involving the zero-point oscillations of the
electromagnetic field surrounding the surfaces. These fluctuations
exert a "radiation pressure" on the surfaces and the overall force is
weaker in the gap between the surfaces than elsewhere, drawing the
surfaces together. Tiny though it is, the Casimir effect becomes
significant at distances of micrometres or less and actually causes
parts in nano- and micro-electromechanical systems (NEMS and MEMS) to
stick together.
Now, Leonhardt and Philbin have calculated that the
Casimir force between two conducting plates can turn from being
attractive to repulsive if a "perfect" lens is sandwiched between them.
A perfect lens can focus an image with a resolution that is not
restricted by the wavelength of light. Such a lens could be made from a
metamaterial made of artificial structures that are engineered to have
negative index of refraction -- which means that the metamaterial bends
light in the opposite direction to an ordinary material.
According to
the researchers, the negative-index metamaterial is able to modify the
zero-point oscillations in the gap between the surfaces, reversing the
direction of the Casimir force. Indeed, the researchers believe that
this repulsive force is strong enough to levitate an aluminium mirror
that is 500nm thick, causing it to hover above a perfect lens placed
over a conducting plate. Since the Casimir force acts on the length
scale of nanomachines, manipulating it could be important for future
applications of nanotechnology.
"In the nano-world, the Casimir force
is the ultimate cause of friction," Leonhardt told physicsworld.com.
"Our result means we could now envision frictionless machines or novel
micromotors." While physicists have had some success creating perfect
lenses from negative-index metamaterials, the technology is still in
its infancy. "The work points towards new applications of left-handed
materials that are not strictly optical," says Federico Capasso of
Harvard University, who studies the effect of the Casimir force on
MEMS. "However, the materials are not easy to make so the concept may
take a few years to realise."'
Source: Physicsworld Via: http://physicsworld.com/cws/article/news/30670
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