Difference between revisions of "Superlubricity"
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| − | '''Superlubrication''' is a state of extremely low friction that occurs when two atomically precise surfaces slide along each other in such a way that the "atomic bumps" do not mesh or more precisely when the lattices distances projected in the direction of movement are maximally incommensurate. | + | '''Superlubrication''' is a '''state of extremely low friction''' that occurs when '''two atomically precise surfaces slide along each other''' in such a way that the '''"atomic bumps" do not mesh''' or more precisely when the lattices distances projected in the direction of movement are maximally incommensurate. |
exapmples: | exapmples: | ||
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If the surface pressure isn't extremely high the characteristic thermal energy k<sub>B</sub>T can become a lot higher than the bumps energy barriers. | If the surface pressure isn't extremely high the characteristic thermal energy k<sub>B</sub>T can become a lot higher than the bumps energy barriers. | ||
Thus the friction becomes so low that e.g. an unconstrained [[diamondoid molecular elements|DMME]] bearing can be activated thermally and may starts turning randomly in a [https://en.wikipedia.org/wiki/Brownian_motion Brownian] fashion. | Thus the friction becomes so low that e.g. an unconstrained [[diamondoid molecular elements|DMME]] bearing can be activated thermally and may starts turning randomly in a [https://en.wikipedia.org/wiki/Brownian_motion Brownian] fashion. | ||
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| + | Note that there is not a sharp cutoff like in superconductivity. | ||
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| + | Interestingly Van der Waals forces allow for stable designs in which the axle in [[diamondoid molecular elements|DMME]] bearings is pulled outward in all directions instead of compressed inward | ||
Revision as of 16:16, 16 December 2013
Superlubrication is a state of extremely low friction that occurs when two atomically precise surfaces slide along each other in such a way that the "atomic bumps" do not mesh or more precisely when the lattices distances projected in the direction of movement are maximally incommensurate.
exapmples:
- two coplanar sheets of graphene relatively rotated to one another
- two appropriately chosen coaxial nanotubes
- diamondoid molecular bearings and other DMEs with sliding interfaces.
If AP surfaces surfaces are designed or aligned to not mesh the "perceived bumps" become lower and their spacial frequency becomes higher. If the surface pressure isn't extremely high the characteristic thermal energy kBT can become a lot higher than the bumps energy barriers. Thus the friction becomes so low that e.g. an unconstrained DMME bearing can be activated thermally and may starts turning randomly in a Brownian fashion.
Note that there is not a sharp cutoff like in superconductivity.
Interestingly Van der Waals forces allow for stable designs in which the axle in DMME bearings is pulled outward in all directions instead of compressed inward
