Secret of Levitation - Reverse Friction

[Justforfun000]

Scientists reveal secret of levitation

Mon Aug 6, 9:27 AM ET

Scientists have discovered a ground-breaking way of levitating ultra small objects, which may revolutionise the design of micro-machines, a new report says.

Physicists said they can create "incredible levitation effects" by manipulating so-called Casimir force, which normally causes objects to stick together by quantum force.

The phenomenon could be used to improve the performances of everyday devices ranging from car airbags to computer chips, say Professor Ulf Leonhardt and Dr Thomas Philbin from Saint Andrews University.

Casimir force -- discovered in 1948 and first measured in 1997 -- can be seen in a gecko's ability to stick to a surface with just one toe.

Now the British scientists say they can reverse the Casimir force to cause an object to repel rather than attract another in a vacuum.

"The Casimir force is the ultimate cause of friction in the nano world, in particular in some micro-electromechanical systems," said Leonhardt, writing in the August issue of New Journal of Physics.

"Micro or nano machines could run smoother and with less or no friction at all if one can manipulate the force," he added.

And he added: "In order to reduce friction in the nanoworld, turning nature's stickiness into repulsion could be the ultimate remedy. Instead of sticking together, parts of micromachinery would levitate."

Leonhardt stressed that the practise is possible only for micro-objects.

But he underlined that, although in principle it may one day be possible to levitate humans, that day is a long way off.

"At the moment, in practice it is only going to be possible for micro-objects with the current technology, since this quantum force is small and acts only at short ranges," he said.

"For now, human levitation remains the subject of cartoons, fairytales and tales of the paranormal."

Their research was to be published in the New Journal of Physics.

http://news.yahoo.com/s/afp/20070806/wl ... Ko4bX9xg8F

[SirNitram]

As someone who argued you couldn't use the Cashimir Effect to push, only to pull....

Coolest egg on face, ever.

[Molyneux]

But...HOW do they manipulate the Casimir force? The article doesn't say!

[Gigaliel]

But...HOW do they manipulate the Casimir force? The article doesn't say!

In the most abstract sense possible, put two things really, really close together. That's about it. The geometries involved determine whether it's attractive/repulsive/weird. Two electrically neutral plates gets you an attractive force when put really, really close to each other (gravity is ludicrously weak on nanoscales, so it can be safely ignored).

[Winston Blake]

It's probably related to this:

Perfect lens could reverse Casimir force

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.
Hamamatsu

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."

I don't know anything about this stuff, but a negative index of refraction means the phase velocity of light between the plates is going to be greater than c. Now v = f*wavelength, so if we assume that the frequency of a given standing-wave mode stays the same, and the velocity increases, then the wavelength must decrease.

Since the Casimir effect is supposed to happen because you can't fit large wavelengths between the plates, then in my naive imagination this mechanism would be a way of 'shrinking' all the wavelengths so you can fit more in. If you pack in 'more' than exist outside the plates, then you'd get a repulsive force.

[Winston Blake]

Crap, it must be the other way around - wavelength staying constant while frequency is increased. The gap between the plates limits the wavelength, so if you allow higher frequencies then you can fit more modes in. Blergh.

[Howedar]

It's exceedingly likely that this is one of those cool-in-the-lab things that has no actual application in the real world.

[Academia Nut]

Actually, one of the big things that pose a difficulty for nanotech is something they like to colloquially call "sticktion", which is the nanoscale interaction of molescules and friction. Sometimes you will get two parts to a micromachine too close together and due to the Casimir effect they will slam together and then form permanent inter-atomic bonds, permanently fucking up what you were trying to assemble. This could have big benefits for nanotechnology in the long run.

[Molyneux]

It's exceedingly likely that this is one of those cool-in-the-lab things that has no actual application in the real world.

Like what?

[Darth Holbytlan]

It's exceedingly likely that this is one of those cool-in-the-lab things that has no actual application in the real world.

So far, it sounds more like one of those cool-on-paper things that has no actual application in the lab...

[Zixinus]

To me, it sounds one of those theoretical musings that sounds cool but turns out to not work, revealing a more complex mechanism of the universe that offers a much greater potential use.

[sketerpot]

It's exceedingly likely that this is one of those cool-in-the-lab things that has no actual application in the real world.

According to the physicsworld article, this could be very useful in MEMS technology -- and it has yet to be observed in the lab.

[Howedar]

Yes, I know. It's 100% prediction on my part, not 50%.