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MEMS Researchers Hope To Exploit Casimir Effect
smartalix writes "Researchers at Purdue University's School of Science are examining the Casimir effect (a phenomenon that explains Max Planck's and Werner Heisenberg's quantum vacuum fluctuation theory) and its impact on nanostructures in MEMS devices. At the distances these structures such as gear teeth, actuators, and such) will be operating from one another, the Casimir force may become something to reckon with, potentially forcing a limit to the level of miniaturization possible. The Purdue team is not only confirming Casimir's original theory, it is exploring possible ways to harness the effect in micromachines."
Here's the on-topic part of my comment, (for moderation purposes), NIGGERS.
It's spelled C-A-S-H-M-E-R-E.
Wouldn't a better use of the casmir force be instantanoius communication.
Well, someone had to say it!
I have no idea what Heisenberg's Quantum Vacuum Fluctuation Theory is. I'm pretty sure there's no such thing. And the Casimir Effect is more a consequence of quantum field theory which was largely pioneered by workers after Heisenberg. Vanilla quantum mechanics itself doesn't predict the Casimir effect.
And going along with what Feynman had to say about miniaturization: the Casimir effect doesn't set limits. On the contrary it is another force that engineers can work with to get what they want done. Forces are good - they give interactions between parts. No interactions, no machine. It does mean you have to throw out even more of your classical mechanics intuition and replace it with a quantum one. That can only be good.
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Did anyone else go back throught the story description and read it like John Moshitta used to do in the Micro Machines commercials?
MicroMachinesMicroMachinesMicroMachines!!!
--"The perfect example of the man of action is the suicide." - William Carlos Williams
the Casimir effect (a phenomenon that explains Max Planck's and Werner Heisenberg's quantum vacuum fluctuation theory)
:) Quantum theory is full of such unhelpful infinities -- it was working out how to get rid of them ("renormalisation") that won Feynman his Nobel prize.
Whoa there, you've got it all backwards. The Casimir effect is EXPLAINED BY quantum vacuum fluctuations, though the description of the effect in the original article is so bad that I can forgive your misunderstanding.
First, let's get the names right. It was Heisenberg and Schrodinger (not Planck) who came up with the first quantum theory to predict vacuum energy. However the idea of this energy coming from virtual particles (or "spontaneously appearing and disappearing particles and photons" as the article puts it) comes from Dirac's theory of quantum electrodynamics, as perfected by Feynman, Tomonaga and Schwinger. There's no independent "quantum vacuum fluctuation theory".
Second, let's have a closer look at the physics. The article gets the basic idea right: two parallel plates close together are pushed together because there are less virtual particles between the plates than outside them. The detail, though, is wrong - photons do not "pile up" outside the plates. It's much simpler than that. In an (infinite) vacuum, photons can exist with any wavelength. But between two plates, photons can only exist with wavelengths that are simple multiples of the distance between the plates -- just like vibrations on a finite string. (So it's not simply a case of only longer wavelenths being excluded--shorter ones are too, unless they're the right length) Both inside and outside, each permitted wavelength will on average be occupied by the same number of "virtual" photons caused by vacuum fluctuations. Because there are less wavelengths permissible between the plates than outside them, there's overall a greater energy density outside, which translates into a higher pressure.
The more perspicacious reader will have noted that there's an infinite number of possible wavelengths outside, and a (smaller) infinity of permitted wavelengths inside, with the difference between the two being infinite. Since each wavelength carries the same (finite) amount of vacuum energy, doesn't this mean that the energy density of the vacuum is infinite and that the force between the two plates is infinite... Well, yes and no. It depends what you mean by infinity
One interested but little-known point about the Casimir effect is that it's not always attractive -- depending on the geometry of the components involved it can also be repulsive. However working out the result except in the most simple geometries is a VERY difficult problem...
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This talk of "virtual" photons is pretty fictitious. The Casimir effect is computed from the zero-point field ie. the lowest energy state for each wavelength. Ie. it's computed assuming no real photons. But I don't see where "virtual" photons come in either. You don't need to do any Feynman diagram computations to get the result. "Virtual" photons are just labels given to edges in Feynman graphs. No perturbation, no need to talk of "virtual" photons.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
I stopped reading the EE Times article after this stupid mistake:
As computer chips increasingly make use of photons (instead of electrons) to carry data...
Computer chips don't use electrons to carry data; they use photons. If getting a bit from one side of the chip to the other required moving an electron, we'd be hearing about Intel's new 4 Hertz processor next week.
Computer chips don't use electrons to carry data; they use photons.
Yes they do use electrons you dork.
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The only Casimir effect i've heard of nearly lobotomized a whole generation of french kids 25 years ago !
There are some nice write ups on it at everything2. Just take a look there.
-><- no
You are correct, but I doubt many people will realize it unless you explain it (or they think long and hard). For the non-physics majors out there:
Electrons have mass, and thus move very slowly compared to photons, which don't have mass and thus move at the speed of light. Among their other duties, photons carry the replusive and attractive forces we associate with charged objects such as ellections (as most of us had to memorize at some point, opposites attract and like-charges repel).
So how does this move data? To grossly oversimplify, when an electron moves down a wire (or through a semiconductor, or whatever) it emits a photon that goes rushing on ahead, and eventually encounters an other electron, which (because of the repulsive force of the electron coming towards it) starts moving in the same direction. The process continues all the way down the wire, with almost all of the distance being covered by the travel of photons. Thus we see the signal moving (via the photons) at a significant fraction of the speed of light even though the electrons themselves are poking along much more slowly.
-- MarkusQ
It's worth noting that many problems can be solved perturbatively in different ways leading to completely different sets of Feynman diagrams and hence different virtual particles. A good example is the use of ghost particles in gauge theory.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
Isn't the Casimir Effect supposed to be unexploitable for useful work (or net work)? Because if you could exploit it, you'd violate Carnot's Law, and create a perpetual motion machine... violating the laws of thermodynamics.
Unlike that lightsail argument before, this really would be a heat engine, exploiting ambient energy / zero point energy.
...who modded that down to -1, Interesting.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
Interestingly, the Casimir effect also occurs in biological systems. Proteins embedded in a lipid membrane restrict the fluctuations of the membrane and therefore decrease the entropy in the region between the proteins. Since thermal systems evolve toward maximum entropy, the proteins move toward each other. Here the fluctations are thermal instead of quantum mechanical, and the medium is the membrane instead of the vacuum, but the principle is the same.
If you google for "casimir membrane" you'll find a lot of papers on the subject.
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