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Metamaterials reverse casimir force|
Posted on Saturday, August 04, 2007 @ 16:05:10 GMT by vlad
Sigma writes: 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
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.
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."'
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|Re: Metamaterials reverse casimir force (Score: 1)|
by Koen on Tuesday, August 07, 2007 @ 23:11:17 GMT
(User Info | Send a Message) http://no.nl/tesla
|Casimir effect in hyperbolic polygons (Score: 1)|
by vlad on Wednesday, August 08, 2007 @ 09:36:36 GMT
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|Casimir effect in hyperbolic polygons|
Feza Gursey Institute, PO Box 6, 81220 C¸ engelk¨oy, Istanbul, Turkey
Received 10 April 2007, in final form 10 June 2007
Published 7 August 2007
Online at stacks.iop.org/JPhysA/40/10611
Using the point splitting regularization method and the trace formula for the spectra of quantum–mechanical systems in hyperbolic polygons which are the fundamental domains of discrete isometry groups acting in the two-dimensional hyperboloid we calculate the Casimir energy for massless scalar fields in hyperbolic polygons. The dependence of the vacuum energy on the number of vertices is established.
Abstract: http://www.iop.org/EJ/abstract/-alert=29097/1751-8121/40/34/016 [www.iop.org]
Full text PDF: http://www.iop.org/EJ/article/-alert=29097/1751-8121/40/34/016/a7_34_016.pdf [www.iop.org]
|Articles on Casimir force manipulation (Score: 1)|
by vlad on Saturday, January 17, 2009 @ 17:56:30 GMT
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|Casimir effect for massive photons|
G. Barton & N. Dombey
School of Mathematical and Physical Sciences, University of Sussex, Falmer, Brighton BN1 9QH, UK
The suggestion that the force between two perfectly conducting plates in quantum electrodynamics depends critically on whether the photon mass is precisely zero or not is false. The solution to this problem involves the discovery of a new class of classical solutions for the electromagnetic field between conducting plates, when the photon has non-zero mass.
Source: http://www.nature.com/nature/journal/ [www.nature.com]-------------------------
Quantum physics: Casimir force changes sign
Eyal Buks & Michael L. Roukes
This quantum attractive force induces measurable effects between ultrasmall mechanical components. New calculations indicate that systems could be engineered in which Casimir forces are repulsive.
Quantum physics: Quantum force turns repulsive
Steve K. Lamoreaux
The experimental verification that a bizarre quantum effect — the Casimir force — can manifest itself in its repulsive form is pivotal not only for fundamental physics but also for nanotechnology.
Measured long-range repulsive Casimir–Lifshitz forces
J. N. Munday, Federico Capasso & V. Adrian Parsegian
Quantum fluctuations create intermolecular forces that pervade macroscopic bodies. At molecular separations of a few nanometres or less, these interactions are the familiar van der Waals forces. However, as recognized in the theories of Casimir, Polder and Lifshitz, at larger distances and between macroscopic condensed media they reveal retardation effects associated with the finite speed of light. Although these long-range forces exist within all matter, only attractive interactions have so far been measured between material bodies. Here we show experimentally that, in accord with theoretical prediction, the sign of the force can be changed from attractive to repulsive by suitable choice of interacting materials immersed in a fluid. The measured repulsive interaction is found to be weaker than the attractive. However, in both cases the magnitude of the force increases with decreasing surface separation. Repulsive Casimir–Lifshitz forces could allow quantum levitation of objects in a fluid and lead to a new class of switchable nanoscale devices with ultra-low static friction.