Difference between revisions of "How friction diminishes at the nanoscale"

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{{stub}}
 
{{stub}}
  
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'''Wrong!''' you think? <br>
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While the total surface area per volume of bearings in nanomachinery rises
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Well yes, in the context of [[rising surface area]] friction really does rise when going down to the the nanoscale, but ...
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there are other factors that more than compensate for that
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* ... that is only if we'd fill up a whole macroscopic volume densely with nanomachinery (not necessary in [[convergent assembly]]) and
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* ... in other regards it shrinks.
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First there is [[superlubricity]], <br>
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but there are other perhaps more deep reasons for friction to diminish at the nanoscale.
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Its about the issue that in systems small enough
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* there are few degrees of freedom for energy to be dispersed into (thermalized/devaluated/dissipated) and
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* there can be the quantum effect of a minimum activation energy that needs to be overcome before a degree of freedom becomes available. <br>(This can be seem in the plots of heat capacity over temperature for polyatomic gases where steps represent the "quantum activation" of degrees of freedom).
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{{wikitodo|Elaborate on that here. A lot is in the as of yet unpublished ReChain zim-wiki}}
 
{{wikitodo|Elaborate on that here. A lot is in the as of yet unpublished ReChain zim-wiki}}
  
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== Related ==
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= Factors reducing friction of gemstone based nanomachinery =
 +
 
 +
The main (over)compensating factors for rise in friction from [[higher bearing surface area of smaller machinery]] are: <br>
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* (1) [[Convergent assembly]] or equivalently ...
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* (2) [[Higher throughput of smaller machinery]] and ...
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* (X) [[Superlubricity]]
 +
 
 +
== Falling friction from "[[convergent assembly]]" ==
 +
 
 +
* In first approximation all convergent assembly layers have the same total bearing area as the top macroscale one
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* There is no need for a large number of convergent assembly layers
 +
 
 +
And diverging from that first approximation: <br>
 +
A bottom layer stacked of chambers of the same size only further reduces friction
 +
 
 +
This trick gives a tuning parameter of: nanomachinery_operation_speed times bearing_area per chip_area. <br>
 +
{{wikitodo|elaborate on that}}
 +
 
 +
== Falling friction from "[[higher throughput of smaller machinery]]" ==
 +
 
 +
To reach practical levels of throughput <br>
 +
there is not no need to fill up the whole of the macroscale assembly chamber with nanomachinery. <br>
 +
The "volumetric throughput density" (how much product per time can be processed per how much volume of nanomachinery) of gemstone based nanomachinery is very high.
 +
 
 +
Note: ''This is the same effect as in the former section but in different formulation.'' <br>
 +
Basically tracing down [[convergent assembly]] one finds high volumetric throughput density.
 +
 
 +
== [[Superlubricity]] ==
 +
 
 +
This one is a bit of a mystery. <br>
 +
 
 +
=== Static friction or dynamic drag? ===
 +
 
 +
This is likely about static classical friction µ rather than dynamic drag.
 +
 
 +
Friction from dynamic drag (per unit of area) can actually be quite high when looking at higher speeds. <br>
 +
But is can become very low for low speeds. And low speeds are very affordable to choose, <br>
 +
because there is plenty of space for more nanomachinery.
 +
This just increases a nanoscale thickness layer to a microscale thickness layer at worst.
 +
 
 +
=== Low friction despite notches matching up with grooves ===
 +
 
 +
Even in cases where grooves and notches of shaft and sleeve match up (commensurate situation) <br>
 +
low friction can be present. It's just essential that the notches and grooves are stiff enough <br>
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* for the energy to be completely recuperated when going across a notch-facing-notch-barrier.
 +
* for there to be no [[snapback]]
 +
<small>(Technical formulation: one needs a conservative energy potential.")</small>
 +
 
 +
At the macroscale a strong waviness of potential over the turning angle <br>
 +
(like e.g. felt when turning a shaft of a stepper motor) <br>
 +
most definitely leads to higher dissipation. <br>
 +
Especially a light rotor does not turn long in face of strong waviness of potential.<br>
 +
But this dissipation mostly comes from a non stiff damping coupling of the sleve to the surrounding framework.
 +
Especially it this surrounding framework is a human Hand.
 +
 
 +
In [[Nanosystems]] dissipation from acoustic radiation has been analyzed and found to be not a dominant
 +
contributor for the targested operational speed range (~5mm/s).
 +
 
 +
Waviness of potential not necessarily meaning higher energy dissipation losses <br>
 +
is good news for molecular gears with tooth made up of single rows of atoms. <br>
 +
These are harder design to have get atom count incommensurability. <br>
 +
<small>(Well not impossible with herringbone style gears probably {{todo|design one}})</small>
 +
 
 +
= Misc =
 +
 
 +
There are other perhaps more deep reasons for friction to diminish at the nanoscale.
 +
It's about the issue that in systems small enough ...
 +
* there are few degrees of freedom for energy to be dispersed into (thermalized/devaluated/dissipated) and
 +
* there can be the quantum effect of a minimum activation energy that needs to be overcome before a degree of freedom becomes available. Likely only relevant for low temperature applications.<br>(This can be seem in the plots of heat capacity over temperature for polyatomic gases where steps represent the "quantum activation" of degrees of freedom).
 +
 
 +
= Related =
  
 
* [[Low speed efficiency limit]] {{wikitodo|maybe move stuff over to here?}} ''the interplanetary analogy'' ...
 
* [[Low speed efficiency limit]] {{wikitodo|maybe move stuff over to here?}} ''the interplanetary analogy'' ...

Revision as of 09:58, 17 September 2021

This article is a stub. It needs to be expanded. 
While the total surface area per volume of bearings in nanomachinery rises 
there are other factors that more than compensate for that

(wiki-TODO: Elaborate on that here. A lot is in the as of yet unpublished ReChain zim-wiki)

Factors reducing friction of gemstone based nanomachinery

The main (over)compensating factors for rise in friction from higher bearing surface area of smaller machinery are:

Falling friction from "convergent assembly"

  • In first approximation all convergent assembly layers have the same total bearing area as the top macroscale one
  • There is no need for a large number of convergent assembly layers

And diverging from that first approximation:
A bottom layer stacked of chambers of the same size only further reduces friction

This trick gives a tuning parameter of: nanomachinery_operation_speed times bearing_area per chip_area.
(wiki-TODO: elaborate on that)

Falling friction from "higher throughput of smaller machinery"

To reach practical levels of throughput
there is not no need to fill up the whole of the macroscale assembly chamber with nanomachinery.
The "volumetric throughput density" (how much product per time can be processed per how much volume of nanomachinery) of gemstone based nanomachinery is very high.

Note: This is the same effect as in the former section but in different formulation.
Basically tracing down convergent assembly one finds high volumetric throughput density.

Superlubricity

This one is a bit of a mystery.

Static friction or dynamic drag?

This is likely about static classical friction µ rather than dynamic drag.

Friction from dynamic drag (per unit of area) can actually be quite high when looking at higher speeds.
But is can become very low for low speeds. And low speeds are very affordable to choose,
because there is plenty of space for more nanomachinery. This just increases a nanoscale thickness layer to a microscale thickness layer at worst.

Low friction despite notches matching up with grooves

Even in cases where grooves and notches of shaft and sleeve match up (commensurate situation)
low friction can be present. It's just essential that the notches and grooves are stiff enough

  • for the energy to be completely recuperated when going across a notch-facing-notch-barrier.
  • for there to be no snapback

(Technical formulation: one needs a conservative energy potential.")

At the macroscale a strong waviness of potential over the turning angle
(like e.g. felt when turning a shaft of a stepper motor)
most definitely leads to higher dissipation.
Especially a light rotor does not turn long in face of strong waviness of potential.
But this dissipation mostly comes from a non stiff damping coupling of the sleve to the surrounding framework. Especially it this surrounding framework is a human Hand.

In Nanosystems dissipation from acoustic radiation has been analyzed and found to be not a dominant contributor for the targested operational speed range (~5mm/s).

Waviness of potential not necessarily meaning higher energy dissipation losses
is good news for molecular gears with tooth made up of single rows of atoms.
These are harder design to have get atom count incommensurability.
(Well not impossible with herringbone style gears probably (TODO: design one))

Misc

There are other perhaps more deep reasons for friction to diminish at the nanoscale. It's about the issue that in systems small enough ...

  • there are few degrees of freedom for energy to be dispersed into (thermalized/devaluated/dissipated) and
  • there can be the quantum effect of a minimum activation energy that needs to be overcome before a degree of freedom becomes available. Likely only relevant for low temperature applications.
    (This can be seem in the plots of heat capacity over temperature for polyatomic gases where steps represent the "quantum activation" of degrees of freedom).

Related

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