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Casimir force used by MEMS, will affect nanotech

from the top-down-pathway dept.
ScienceExpress, an online preprint service (login req'd) of Science magazine, published on Feb. 8 a report from Bell Labs/Lucent that MEMS can exploit the Casimir force. Coauthor Federico Capasso was quoted in the Feb. 10 Science News: "Capasso speculates that makers of MEMS and even tinier nanoelectromechanical systems may find ways to harness the Casimir force in 5 to 15 years…the experiment also indicates that the Casimir effect may become problematic for designers of tiny machines, says Paul J. McWhorter of MEMX…" CP: What's problematic to some may be a fun challenge to others — anyone care to give their view on this? Read more for the abstract. Abstract from ScienceExpress:

"The Casimir force is the attraction between uncharged metallic surfaces due to quantum mechanical vacuum fluctuations of the electromagnetic field. We demonstrate the Casimir effect in microelectromechanical systems using a micromachined torsional device. Attraction between a polysilicon plate and a spherical metallic surface results in a torque that rotates the plate about two thin torsional rods. The dependence of the rotation angle on the separation between the surfaces is in agreement with calculations of the Casimir force. Our results show that quantum electrodynamical effects play a significant role in such microelectromechanical systems when the separation between components is in the nanometer range."

3 Responses to “Casimir force used by MEMS, will affect nanotech”

  1. Enon Says:

    Nanosystems

    I don't have a copy of Nanosystems at the moment, but I believe Drexler addressed this issue, perhaps under the name of van der Walls or London dispersion force. (I'm not sure of the technical difference, if any, between these and the Casimir force. Any experts out there?) These forces seem to be extraordinarily small compared to other forces at work in a nano-device, so they shouldn't be showstoppers. For the same reason they seem unlikely to lead to attractive energy storage methods. The Casimir force has never been shown to be anything but conservative so they won't be a source of energy as some have speculated .

  2. MarkGubrud Says:

    Casimir forces

    Casimir and Van der Waals forces are both manifestations of corrlated charge density fluctuations; the difference is mainly geometry and context. Van der Waals attraction between molecules (small dipoles) varies roughly as the sixth power of separation, while Casimir attraction between flat conducting plates (charge patches) varies as the fourth power of separation.

    Van der Waals forces are very important at the molecular scale, while Casimir forces are insignificant at the micron scale of current MEMS, so one can immediately infer that these forces must become significant at some intermediate length scale, probably in the low nanometer range.

    In any case, it's hard to see an argument why this consideration would be a showstopper for nanotech at any scale. I also don't see any particularly clever uses for it. Robert Forward proposed a Casimir-effect battery some years ago, mainly to argue that one could, in principle, extract "vacuum energy", albeit only once before you have to recharge the battery. Based on Forward's numbers, I calculated that a Casimir D cell would weigh about 30 tons.

  3. guybar Says:

    Re:Nanosystems

    If I'm not mistaken, van-der-vaals force is due to temporary electric-dipole moment in an atom (molecule) inducing another such at a neighbour atom, it is a chemical phenomena. The casimir effect is a pure QED effect, caused the vacuum state being "not empty", i.e. even in the vacuum there's a non-zero probability of EM fluctuations, it is AFAIK unrelated with charge distribution.

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