significance of casimir force
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Casimir Rack and Pinion R amin Golestanian Department of Physics and Astronomy University of Sheffield. Significance of Casimir Force. Tiny at Micron-scale It took 50 years to be verified! Dominant at Nano-scale Strongest distance dependence unwanted effects: stiction - PowerPoint PPT PresentationTRANSCRIPT
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Casimir Rack and Pinion
Ramin GolestanianDepartment of Physics and Astronomy
University of Sheffield
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Significance of Casimir Force
• Tiny at Micron-scaleIt took 50 years to be verified!
• Dominant at Nano-scaleStrongest distance dependence
unwanted effects: stiction
harnessed for good use: novel NEMS
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Geometry Challenge
• Practical AspectRealistic ``machine parts’’
• Fundamental AspectPair-wise summation?
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Geometry Challenge
• Expansion in Dielectric Contrast
R. Golestanian, Phys. Rev. Lett. 95, 230601 (2005)
Not so easy …
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Geometry Challenge
• Convergence properties
R. Golestanian, Phys. Rev. Lett. 95, 230601 (2005)
CM:
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Normal Casimir Force
• Is it practical in making nano-mechanical devices?
Not really …
• Repulsive Casimir Force: does it exist?
Alchemy of nano-mechanics …
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Lateral Casimir Force
• Theoretical Prediction
``Josephson-like’’ force between corrugated surfaces
R. Golestanian & M. Kardar, Phys. Rev. Lett. 78, 3421 (1997)
T. Emig, A. Hanke, R. Golestanian & M. Kardar, Phys. Rev. A 67, 022114 (2003)
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Lateral Casimir Force
• Experimental Verification
F. Chen, U. Mohideen, G. L. Klimchitskaya, &V. M. Mostepanenko, Phys. Rev. Lett. 88, 101801 (2002)
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Rack and Pinion
A. Ashourvan, M.F. Miri, & R. Golestanian, Phys. Rev. Lett. 98, 140801 (2007)
Powered by Quantum Vacuum
Force transduction with no contact could potentially solve wear problem in nano-mechanical systems
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Equation of Motion
R
x=R
y
W
H
y
x
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Equation of Motion
Relevant parameters:
Uniformly moving rack:
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No Dissipation
The equation is integrable: nonlinear pendulum
Skipping Velocity:
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No Dissipation
Pinion Velocity vs Rack Velocity and initial Offset
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No Dissipation
The effect of external load on the skipping transition
similar to solid friction
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Weak Dissipation
The skipping transition boundary
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Weak Dissipation
Pinion Velocity vs Rack Velocity and Load
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Strong Dissipation
Pinion Velocity vs Rack Velocity and Load
Stall Force
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Vibrating Rack and Pinion
A. Ashourvan, M.F. Miri, & R. Golestanian, Phys. Rev. E 75, 040103 (R)(2007)
Is it possible to rectify a symmetric oscillatory motion?
See also: T. Emig, Phys. Rev. Lett. 98, 160801 (2007)
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Vibrating Rack and Pinion
Equation of motion:
Pinion Velocity:
Solution:
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Vibrating Rack and Pinion
Basin of attraction for forward motion
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Vibrating Rack and Pinion
Parameter values for forward motion
Stall Force:
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Feasibility
Realistic values for the lateral Casimir force amplitude
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Feasibility
Realistic values for skipping velocity
Not so small after all …
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Conclusion
Casimir forces are dominant at nano-scale ☺
Knowledge of Casimir forces can be used to avoid unwanted effects in NEMS
They can be used to design nano-mechanical devices: mechanical engineering with quantum vacuum fluctuation forces!
Non-contact lateral force transduction can solve the wear problem
Despite expectation, the Casimir grip can be strong
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THANK YOU
Collaborators:
A. Ashourvan (IASBS, Zanjan)M.F. Miri (IASBS, Zanjan)
Acknowledgement: