| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
03 May 2007 10:49:55 PM |
| Object: |
Casimir force could drive tiny ratchets |
Casimir force could drive tiny ratchets (May 2)
http://physicsweb.org/article/news/11/5/4
A physicist in France claims that the Casimir force between two neutral
surfaces could be exploited to create tiny ratchets that could someday
drive machines built at the micrometre scale. Thorsten Emig of the
Université Paris-Sud has designed a ratchet based on surfaces with
special corrugations that can be made to slide past each other in only
direction. Emig claims that Casimir ratchets, *which have yet to* be
built, could be superior to current microratchets, which are based on
the electrostatic forces between charged objects (Phys. Rev. Lett. 98
160801).
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| User: "Uncle Al" |
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| Title: Re: Casimir force could drive tiny ratchets |
04 May 2007 09:52:12 AM |
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Sam Wormley wrote:
Casimir force could drive tiny ratchets (May 2)
http://physicsweb.org/article/news/11/5/4
A physicist in France claims that the Casimir force between two neutral
surfaces could be exploited to create tiny ratchets that could someday
drive machines built at the micrometre scale. Thorsten Emig of the
Université Paris-Sud has designed a ratchet based on surfaces with
special corrugations that can be made to slide past each other in only
direction. Emig claims that Casimir ratchets, *which have yet to* be
built, could be superior to current microratchets, which are based on
the electrostatic forces between charged objects (Phys. Rev. Lett. 98
160801).
Optical fabrication of the ratchet pair is trivial: A laser-generated
diffraction grating and a blazed diffraction grating. Do it on two
small flat silicon wafers, stick one atop the other, and see if the
top one spontaneously translates. Easy.
However... yer gonna need nasty small spacing. If "d" is the flat
surface separation in microns, Casimir force is (0.01300
dyne/cm^2)/d^4. A 500 nm gap (green light) gives 0.208 dyne/cm2 It
is rather worse than that because the surfaces are not 100% reflective
planar superconductors.
Dimensioning ratchets that small will also suffer form the grnaularity
of matter - it's atoms and voids not jellium.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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