The Casimir Effect and Powering Nanotechnology

Updated on April 22, 2012

From early beginnings to achieve work using the Casimir effect, we can now experiment and move forward

The Casimir effect is a small attractive and/or repulsive force that acts between two close parallel uncharged conducting plates and for that matter, also on anything on the nanometre and smaller scale at the atomic-sub-atomic level. It is arises from the quantum vacuum fluctuations of the electromagnetic field.

The effect was predicted from equations worked out by the Dutch physicist Hendrick Casimir in 1948. According to quantum theory, the vacuum continually manifests virtual particles out of the Planck false vacuum, which is in a continuous state of random and chaotic fluctuation. Casimir conceived of an experiment and realized that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. This mirrors the idea of the photoelectric effect, but at much smaller and therefore more energetic levels. The energy density between the plates in his experiment decreases as the plates are moved closer together, which implies that there is a small force either between them drawing them together, or a greater force acting on the sides away from each other. It is actually a combination of both where the number of whole wavelengths between the plates decreases as they move together, while on the sides facing away from between them remains constant. This imbalance of forces is what moves the plates together and the closer they are, the greater the imbalance and the more the force applies. However, this is limited to extremely small distances, where two similarly small objects are close together.

The Casimir force between two plates of area A separated by a distance L can be calculated to be,

```                  π h c
F = ------- A 1
480 L4
```

Where h is Planck's constant and c is the speed of light.

h = 6.626068 × 10 -34 m 2 kg / s

c = 299,792,458 m/s = 1 Planck unit

The tiny Casimir force was measured in 1996 by Steven Lamoreaux in a specially designed experiment. The experimental results were in agreement with the theory to within an experimental uncertainty of plus or minus 5%.

Continually manifesting virtual particles other than the photon also contribute a small effect but only the photon force is measurable. All bosons such as photons produce a Casimir force while fermions make a repulsive contribution. These two opposing forces, when isolated can have profoundly usefal implications in the field of nanotechnology if mastered and we will shortly investigate that possibility. If electromagnetism was super-symmetric there would be fermionic photinos whose contribution would exactly cancel that of the photons and there would be no Casimir effect. The fact that the Casimir effect demonstratively exists shows that if super-symmetry exists in nature it must at least be a broken symmetry. A broken symmetry implies among other things, why matter predominates over anti-matter and allows for the existence of the cosmos.

According to the theory that now has the backing of experiment, the total zero point energy in the vacuum is infinite when summed over all the possible photon modes. The Casimir effect comes from a difference of energies in which the infinities cancel. The energy of the vacuum is a puzzle in theories of quantum gravity since it should act gravitationally and produce a large cosmological constant which would cause space-time to curl up infinitely small and not allow for the existence of the cosmos as we know it. The solution to the this inconsistency is expected to be found in a theory of quantum gravity. However, since we know that the Casimir effect has the energy to move things together or apart in the nanotechnology level, we may be able to use it to power very tiny machines as some experiments suggest as possible.

“Researchers have persuaded a force, called the Casimir effect, to slide tiny gold plates past each other. "This should help us exploit this fundamental force on a tiny scale," says Umar Mohideen, a physicist at UC, Riverside. The Casimir effect depends on the fact that on tiny scales, empty space isn't empty at all. Even a total vacuum is filled with a quantum froth of virtual particles that pop in and out of existence. They don't last long enough for us to detect them directly, but in 1948, Dutch physicist Hendrik Casimir predicted that if you put two parallel plates close enough together so the largest particles can't squeeze into the gap, then the net pressure from the extra particles outside would push the plates together. It took until 1996 for physicists to measure the effect directly demonstrating that bizarre quantum action can affect large scale objects in the "real world." But pushing plates together isn't much use to anyone, and the effect even threatens to jam up moving parts in micromachines. Then, in 1997, MIT physicist Mehran Kardar discovered the shape of the plates could have a startling effect. The Casimir force always acts perpendicular to the plane of the plate, so he reasoned that using corrugated plates should persuade the force to move them sideways past each other. Mohideen and his team announced they had measured this lateral force. They placed two corrugated gold plates a few hundred nanometers apart with their peaks and troughs aligned. When they moved the plates slightly out of alignment, they detected a force of a few piconewtons that pushed them back into position. At this point, you don't get out any more energy than you put in, but it's the first time that virtual particles have been cajoled into doing work in this way. The researchers are now trying to generate other effects such as a repulsive force and a dynamic Casimir effect that moves plates back and forth. The team's measurements could also pick up signs of other as yet undiscovered fundamental forces, as well as evidence of extra spatial dimensions that some theorists predict are curled up on a tiny scale. "We should be able to place limits on the size of these effects," says Mohideen.

Now for the exciting part! What if we designed corrugated plates that were always out of alignment while this force constantly attempts to align them. If we had two plates that were corrugated and fashioned where the corrugations were designed from a center point out and spiralled in opposing directions, this should create a motive force as the Casimir effect sought to bring them into an alignment as in the parallel corrugated plate experiment. Further, if these corrugations got wider from the center out, as we see in many natural patterns and the two plates were fixed as a set distance apart at the center, then we may be able to achieve a working nano-turbine that would do useful work based on the Casimir effect. By attaching a shaft to both outside surfaces, we could do one function on one side, and another on the opposite by tapping the opposite spins. We would in effect have a nano-technological dynamo run by the Casimer force and this in turn can propel a nano-machine or generate nano-current in a nano-circuit. This dynamo could directly power and move a micromachine.

Reference:

http://www.scientificamerican.com/article.cfm?id=what-is-the-casimir-effec

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