Difference between revisions of "Friction"

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This page is meant to be a brief overview covering friction in …
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* gemstone based nanotech (dedicated page: [[Friction in gem-gum technology]])
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* existing nanotech (2023)
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* macrsoscale tech
  
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== The issue ==
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__TOC__
  
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With shrinking size of machinery the surface area of this machinery rises.
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== Nanoscale friction ==
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Doubling the surface area doubles the friction (a [[scaling law]]).
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Extrapolating from speeds and friction levels of macroscale machinery leads to impractically high levels of waste heat generation.
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== In gemstone metamaterial technology ==
  
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This is one of the elephants in the room when introducing an audience to advanced APM.
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Despite [[higher bearing surface area of smaller machinery]] <br>
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the [[friction in gem-gum technology]] stays manageable. <br>
  
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Such an extrapolation is the first thing that any person knowledgeable in other micro- and nanotechnologies is likely do.
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'''Friction not being a show-stopper is due to:''' <br>
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Since this is not the only point where a first "quick" glance reveals a strongly discouraging result and experts usually are busy and have little time at hand to dig deeper, the situation sometimes leads these people to quickly deem all nanomachinery impossible, that looks superficially similar to macro scale cog-and-gear-machinery.
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* (1) The throughput density of nanomachinery. – See: [[Higher throughput of smaller machinery]]
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* (2) The fact that dynamic friction of [[atomically precise slide bearing|nanoscale bearing]] drops quadratically with slowdown. – See: [[Superlubricity]]
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There are dissipation mechanisms that scale linear with speed but these are specific to reciprocative motions only.  
  
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Especially using micro-machionery (tech term: MEMS micro-electro-mechanical systems) as scaling trend leads to hugely misleading results.
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=== (1) How nanomachineries innate high throughput density reduces friction ===
  
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== What makes it work despite the issue ==
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[[Higher throughput of smaller machinery]] leads to very little amount of nanomachinery needed <br>
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and thus to reasonably low bearing surface area within that.
  
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There are several effect working against this explosion of friction which are repeatedly overlooked.
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=== (2) How the dynamic character of nanobearing friction can be exploited to reduce friction ===
  
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=== Flawless surfaces drop friction significantly ===
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Given quadratic gains in efficiency one wants to do a [[deliberate slowdown at the lower assembly levels]]
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where this type of friction is present. <br>
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Keeping throughput constant this means one needs to compensate for the loss of throughput with more nanomachinery. <br>
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More nanomachinery means a linear increase in losses. Quadratic gains times linear losses equals linear gains. <br>
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Overall linear gains in efficiency are still good and worth pursue. <br>
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See: [[Increasing bearing area to decrease friction]]
  
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In contrast to etched micro-systems where the relative manufacturing error gets bigger with shrinking size.
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* '''Q:''' But is there enough space for accomodating more nanomachinery?
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Atomically precise machinery has no error
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* '''A:''' Yes, very much so. It's "[[Higher throughput of smaller machinery]]" again.
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allow superlubrication which drops friction at least three orders of magnitude
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=== One needs to slow down anyway to prevent an explosion of productivity ===
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=== Recycle to reduce friction (not applicable to first time production) ===
  
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Rising productivity allows to slow down motion speeds (e.g. to just few mm per second) while keeping throughput constant.  
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Also a good design averts the need to disassemble things down to nanoscopic parts if <br>
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Slowing down to halve the speed drops drops the fiction to a fourth (a quadratic [[scaling law]] – tech term: dynamic drag).
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only larger scale reconfigurations are needed. – See: [[Convergent assembly]] <br>
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This kind of aversion of frictive losses only applies to recycling though. <br>
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Making recycling all the more desirable end economically viable. Nice!
  
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Main article: "[[Higher productivity of smaller machinery]]".
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=== Further reading ===
  
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=== Dropping speeds further by smart arrangements ===
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'''See main page: [[Friction in gem-gum technology]]''' <smalL>This contains quantitaive estimations.</small>
  
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By dividing relative speeds up in several layers each taking a proportional part of the speed
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A bit more detailed but still brief exlanations to these effects/factors <br>
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area goes up, yes, but the drop in speed has a bigger effect.
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can be found on the page [[How friction diminishes at the nanoscale]].
  
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See main article: "[[Infinitesimal bearing]]s"
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== In existing nanotechnologies ==
  
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== Evolved molecular biology is not a proof that diffusion transport is the ideal solution with minimal losses ==
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=== Stiff ===
  
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With those aforementioned effects cog-and-gear nanomachinery could potential feature smaller losses than diffusion driven natural systems (more on that comparison further down). To quantify that more in depth investigations are needed.
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* Pretty much the only case where the above can already be experimentally tested (as of 2021) is in nested nanotubes and sliding graphene sheets.
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* At the microscale with [[MEMS]] there is the issue with [[stiction]]. Which may paint a misleading picture of how friction and wear scales when going down even further the sizescales.
  
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=== The issue ===
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=== Soft ===
  
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Nature is often (probably mostly out of psychological reasons) seen as unsurpassable.
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It's hard to talk about friction is systems that are akin to biological cells. <br>
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But actually it is completely unknowable whether nature as a whole will be "surpassed" by artificial technology in the far future ([[nature vs technology|get side-tracked]]).  
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It's obviously not that there are no energy dissipation losses. <br>
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Regardless of that, specific aspects of nature definitively can (and have been) surpassed by artificial technologies
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There necessarily are other energy devaluating mechanisms that are not "friction". <br>
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(there are [[technology exceeding nature in performance|countless examples]]).
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While in thermally driven diffusion transport there is no "friction" the energy needs to be "expended" at the "pitstops" instead. <br>
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This is necessary in order to prevent reactions and diffusion transports to run backwards. <br>
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Related: [[Arrow of time]].
  
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Evolution ended up with diffusion transport and not cog-and-gear-machinery.
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Stiff artificial nanosystems could be superior to soft nanosystems (natural and artificial) <br>
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Taken the former in to consideration that does by no means imply that this is the best or only solution.
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because they may allow for more complete [[energy recuperation]] <br>
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Actually evolution is facing severe [[Evolution#Limits_of_natural_evolution|limitations]] (lock-in-effect, incrementalism, ...).
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using [[dissipation sharing]]. That is the "energetic change money" is not lost. <br>
  
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(This is only one of the many cases where [[misconceptions|bio-analogies]] can have a problematic effect on perception.)
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Side-note: This only regards comparison of energy efficiency <br>
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not comparison of maximal performances and operational ranges which both <br>
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are clearly vastly superior in stiff nanosystems.
  
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=== Why cog-and-gear transport may be more efficient ===
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== Macroscale friction ==
  
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While diffusion transport features no friction during the transport process itself
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=== Classical friction ===
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diffusion transport is not at all lossless.
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At intermediate passing stations some energy always needs to be converted to heat (tech term: dissipated).
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Otherwise the chemical reactions would not have a preferred direction to go and all the molecular "machinery" would cease to do anything.
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Of course cog-and gear nanomachinery has exactly the same requirement.
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There is classical friction with the friction coefficient µ. <br>
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The big difference is that in biological systems energy often comes in discrete disconnected chunks.  
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Present e.g. in dry sliding sleeve bearings.
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If ther's more than needed the excess is dissipated without being used for some desired effect.
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* This type of friction is in first approximation independent of sliding (or rolling) speed
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In a crude analogy it's like being unable to accept the change money.
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* This type of friction is in first approximation independent of contact area
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* This type of friction is in dependent on normal force (load)
  
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In cog-and-gear nanomachinery everything is linked together in one big [[machine phase]]
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=== Dynamic drag ===
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There energy can be drawn in a continuous rather than discrete fashion.
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The dissipation necessary for forward moving operation (arrow of time) can be
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There is dynamic drag in liquids and gasses. <br>
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balanced and minimized further down to the absolutely unconditionally required minimum.  
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Present e.g. in hydrostatic and hydrodynamic bearings.
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See main article: "[[Low speed efficiency limit]]"
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* This type of friction is dependent on speed
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* This type of friction is dependent on contact area
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* there is dependence on normal force (load) but it requires an extended model.
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=== Macroscale bearings made form gemstone based nanomachinery ===
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This is about the [[gemstone based metamaterial]] that is [[infinitesimal bearing]]s. <br>
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Distributing the speed difference over many layers can give low friction per bearing area even for higher speeds. <br>
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The rising total bearing interface are is overcompensated by the drop in friction from dropping speed. <br>
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Overall '''doubling the thickness of the stack of bearing layers halves the friction'''. <br>
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A inverse proportional linear relationship.
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Practical bearings can have quite thin stacks of bearing layers. <br>
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Thin from the human scale perspective.
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'''Also related here is [[mesoscale friction]] and [[atomically precise roller gearbearing]]s.''' <br>
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Not roller bearings as friction may be too low for that. That is: Superlubricating rollers may slide rather than roll. <br>
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Going to [[atomically precise roller gearbearing]]s should lower friction quite a bit further judging from the per area friction loss levels of macroscale bearings. <br>
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But it also introduces voids and larger runway surface area per bearing eventually reintroducing gradual wear e.g. by radiation hits. <br>
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Atomically tight seals still can prevent any and all gunk from getting in from the outside. So only internal seed-damage can self-amplify. <br>
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Atomically tight seals need contact all around and thus remain a big contributor of friction. <br>
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Still they can be small in surface area compared to the gearbearings runway. <br>
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Runway only contributes to friction at and near the roller contacts. <br>
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'''Identifying a sweet spot for atomically precise gear-bearing size remains an open question.''' <br>
  
 
== Related ==
 
== Related ==
  
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* [[Superlubrication]]
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* '''[[Friction in gem-gum technology]]'''
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* [[Rising surface area]]
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* [[Reciprocative friction in gem-gum technology]]
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* [[Macroscale style machinery at the nanoscale]]
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* [[Friction in diffusion transport]]
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* [[Common misconceptions about atomically precise manufacturing]]
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* '''[[Superlubricity]] reducing friction'''
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* [[How friction diminishes at the nanoscale]]
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* [[Friction mechanisms]]
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* [[Rising surface area]] causing more friction
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* [[Macroscale style machinery at the nanoscale]] – [[Common misconceptions about atomically precise manufacturing]]
 
* [[Feynman path]] – A naive form of scaling down saw blades and drills to the nanoscale (infeasible)
 
* [[Feynman path]] – A naive form of scaling down saw blades and drills to the nanoscale (infeasible)
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* [[Pages with math]]
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* [[Evaluating the Friction of Rotary Joints in Molecular Machines (paper)]]
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* '''[[Mesoscale friction]]'''
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----
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* [[Losses from mechanochemical reactions]]
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* '''[[Wear]]'''
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[[Category:Pages with math]]
  
 
== External links ==
 
== External links ==
Line 86: Line 136:
 
* Evidence of misconception: See section: "Fundamental Concepts" [https://en.wikipedia.org/w/index.php?title=Nanoelectronics&diff=775073056&oldid=770052236 Wikipedia: Nanoelectronics (2017-04-12)] (common false negatives).
 
* Evidence of misconception: See section: "Fundamental Concepts" [https://en.wikipedia.org/w/index.php?title=Nanoelectronics&diff=775073056&oldid=770052236 Wikipedia: Nanoelectronics (2017-04-12)] (common false negatives).
 
* [https://web.archive.org/web/20160322114752/http://metamodern.com/2009/02/10/nanomachines-how-the-videos-lie-to-scientists/ Nanomachines: How the Videos Lie to Scientists] ([[metamodern blog archive|Eric Drexlers metamodern blog]] (archive) 2009-02-10)
 
* [https://web.archive.org/web/20160322114752/http://metamodern.com/2009/02/10/nanomachines-how-the-videos-lie-to-scientists/ Nanomachines: How the Videos Lie to Scientists] ([[metamodern blog archive|Eric Drexlers metamodern blog]] (archive) 2009-02-10)
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== Table of Contents ==
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__TOC__

Latest revision as of 13:27, 1 April 2024

This page is meant to be a brief overview covering friction in …

Nanoscale friction

In gemstone metamaterial technology

Despite higher bearing surface area of smaller machinery
the friction in gem-gum technology stays manageable.

Friction not being a show-stopper is due to:

There are dissipation mechanisms that scale linear with speed but these are specific to reciprocative motions only.

(1) How nanomachineries innate high throughput density reduces friction

Higher throughput of smaller machinery leads to very little amount of nanomachinery needed
and thus to reasonably low bearing surface area within that.

(2) How the dynamic character of nanobearing friction can be exploited to reduce friction

Given quadratic gains in efficiency one wants to do a deliberate slowdown at the lower assembly levels where this type of friction is present.
Keeping throughput constant this means one needs to compensate for the loss of throughput with more nanomachinery.
More nanomachinery means a linear increase in losses. Quadratic gains times linear losses equals linear gains.
Overall linear gains in efficiency are still good and worth pursue.
See: Increasing bearing area to decrease friction

Recycle to reduce friction (not applicable to first time production)

Also a good design averts the need to disassemble things down to nanoscopic parts if
only larger scale reconfigurations are needed. – See: Convergent assembly
This kind of aversion of frictive losses only applies to recycling though.
Making recycling all the more desirable end economically viable. Nice!

Further reading

See main page: Friction in gem-gum technology This contains quantitaive estimations.

A bit more detailed but still brief exlanations to these effects/factors
can be found on the page How friction diminishes at the nanoscale.

In existing nanotechnologies

Stiff

  • Pretty much the only case where the above can already be experimentally tested (as of 2021) is in nested nanotubes and sliding graphene sheets.
  • At the microscale with MEMS there is the issue with stiction. Which may paint a misleading picture of how friction and wear scales when going down even further the sizescales.

Soft

It's hard to talk about friction is systems that are akin to biological cells.
It's obviously not that there are no energy dissipation losses.
There necessarily are other energy devaluating mechanisms that are not "friction".
While in thermally driven diffusion transport there is no "friction" the energy needs to be "expended" at the "pitstops" instead.
This is necessary in order to prevent reactions and diffusion transports to run backwards.
Related: Arrow of time.

Stiff artificial nanosystems could be superior to soft nanosystems (natural and artificial)
because they may allow for more complete energy recuperation
using dissipation sharing. That is the "energetic change money" is not lost.

Side-note: This only regards comparison of energy efficiency
not comparison of maximal performances and operational ranges which both
are clearly vastly superior in stiff nanosystems.

Macroscale friction

Classical friction

There is classical friction with the friction coefficient µ.
Present e.g. in dry sliding sleeve bearings.

  • This type of friction is in first approximation independent of sliding (or rolling) speed
  • This type of friction is in first approximation independent of contact area
  • This type of friction is in dependent on normal force (load)

Dynamic drag

There is dynamic drag in liquids and gasses.
Present e.g. in hydrostatic and hydrodynamic bearings.

  • This type of friction is dependent on speed
  • This type of friction is dependent on contact area
  • there is dependence on normal force (load) but it requires an extended model.

Macroscale bearings made form gemstone based nanomachinery

This is about the gemstone based metamaterial that is infinitesimal bearings.
Distributing the speed difference over many layers can give low friction per bearing area even for higher speeds.
The rising total bearing interface are is overcompensated by the drop in friction from dropping speed.
Overall doubling the thickness of the stack of bearing layers halves the friction.
A inverse proportional linear relationship.

Practical bearings can have quite thin stacks of bearing layers.
Thin from the human scale perspective.

Also related here is mesoscale friction and atomically precise roller gearbearings.
Not roller bearings as friction may be too low for that. That is: Superlubricating rollers may slide rather than roll.
Going to atomically precise roller gearbearings should lower friction quite a bit further judging from the per area friction loss levels of macroscale bearings.
But it also introduces voids and larger runway surface area per bearing eventually reintroducing gradual wear e.g. by radiation hits.
Atomically tight seals still can prevent any and all gunk from getting in from the outside. So only internal seed-damage can self-amplify.
Atomically tight seals need contact all around and thus remain a big contributor of friction.
Still they can be small in surface area compared to the gearbearings runway.
Runway only contributes to friction at and near the roller contacts.
Identifying a sweet spot for atomically precise gear-bearing size remains an open question.

Related

External links

Table of Contents

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