Physics change aware scale transposed prototyping

See also strongly related page: Applicability of macro 3D printing for nanomachine prototyping

This is about using macroscale manufacturing techniques to prototype and/or investigate
future (not yet buildable) atomically precise nanosystems made out of gemstone like compounds.
For this not to be pointless and the results to have at least some semblance of actual future nanosystems
one must be attentive to the changes of physics that occur at these much smaller nanoscales.

For why this makes sense at all despite
natures life (for the most part) not doing cogs-n-gears at the nanoscale
see pages: Macroscale style machinery at the nanoscale & Why gemstone metamaterial technology should work in brief

Under-engineering & over-engineering

(wiki-TODO: Venn diagram of what applies to macroscale what applies to nanoscale and what applies to both scales.)

Avoid under-engineering (forcing macroscale over-engineering)

• small scale limit (i.e. nothing can be smaller than atoms) => e.g. avoid small screws with even finer threads
• effect of thermal motions on mechanical deflections (shouldn't be too much of an issue - so long no mechanosynthesis is involved)
• atomic corrugations (hard to account for, but should be ignorable in many cases - see superlubricity)
• absence of friction (replaced at nanoscale by corrugation sticking - that alone could suffice for positive locking against fall-apart)
• blurry surfaces (but not soft - see next section)
• …

Tolerate over-engineering (as macroscale under-engineering just does not work)

Example #1 (vdW force):
There is no way around over-engineering some parts that otherwise just wouldn't work at the macroscale.
One can at bets try to play some tricks. E.g. absence of the tremendously useful vdW force as on the macroscale can be faked …

• very poorly by gravity (unidirectional and constant long range force vs omnidirectional short range force)
• semi-decently by magnets (requires the integration of magnets - manual prefabrication with what is vitamins in RepRec context)
• perhaps decently by an sufficiently air sucking end-effector

Example #2 (stiffness):
Also one cannot avoid massively over-engineer in strurdiness and bulkiness,
due to macroscale actually being worse for cog-n-gear style machiners than nanoscale in terms of the stiffness aspects.
but to understand this one needs some important context as presented below in the next section.
More discussion on this in section after next.

Important context - right intuition on stiffness

The nominal operation speed scaled effective stiffness of nanosystems
is vastly higher than in macroscale systems due to …

• diamond being vastly stiffer than even the best steel
• proposed operating speeds being ~1000x slower than macroscale robotic motions
• these two effects multiply

It is way too easy to get thoroughly misled on this nanoscale physics aspect for at least two reasons …

• (1) there's a scaling law that says that absolute stiffness actually falls with size
• (2) molecular dynamics simulations show diamondoid machine element mechanisms jiggle around like jelly.

But …

• (1) What actually matters is the lesser known scaling law of same relative deflections across scales
• (2) MD simulations are necessarily run at excessively high speeds …

See page: Misleading aspects in animations of diamondoid molecular machine elements
And page: A better intuition for diamondoid nanomachinery than jelly

(wiki-TODO: Eventually define nominal operation speed scaled effective stiffness mathematically precisely! Using the same relative deflections across scales law.)

Macroscale systems can't be made anywhere near as filigree as nanosystems (and micro-systems) could be made

No matter what macroscale material one picks,
macroscale materials are soft like jelly compared to systems made out of crystolecules operated at proposed speeds.
adding to that are gravitational loads present on the slightly larger (meters) macroscale that need to be counteracted against.

---

Caveat: For nanosystems that are supposed to do mechanosynthesis one still will
want to stay bulky in order to keep thermal motion amplitudes minimal.

Manufacturing methods for the prototyping - PROs & CONs

Shoestring budget DIY home accessible:

• FFF/FDM 3D printing (CON bigger parts & less accurate layers, PRO more strong plastics options)
• SLA (resin) 3D printing (PRO smaller parts & more accurate layers parts, CON lesser strong plastics options)
• plastic injection molding (there are some affordable DIY machines around by now 2025,
  (PRO some tough plastics can be used that hardly can be printed as they do not stick well HDPE, POM, PTFE, PP, PA, … ~ 3D printer filament printability)
• casting resin (G27 2compunent PU - EU legal access restrictions for private customers?, CON lesser strong plastics options)
• Meh: laser-cutting (via maker-space, mostly way too restrictive in possible geometries)

Industrial:

• industrial metal 3D printing (too expensive, cheapest most viable: aluminum)
• subtractive CNC milling (too expensive)
• Aluminum die casting

Exotic:

• Galvanic methods like (electroforming) …
• DIY Solvent evaporation casting?
• DIY compression molding?

Neither fish nor fowl - multi application case issue

Prototypes systems may turn out to potentially also be useful in other contexts such as e.g. …

• robotic in space systems and
• local DIY home robotic systems

… but this will put a forcing function on
culling back on intentional over-engineering for nanoscale compatibility.

Calling for the integration of "vitamins" like e.g.
small screws that'd become subatomic in size when scaled down.

Calling for the removal of some things.
(wiki-TODO: Remember what I had in mind here.)

Allowed types of cheating

Adding in metal ball/roller bearings where, when scale transposed down to nanoscale, the balls/rollers would become smaller than atoms may actually be an OK case as such ball bearings could be replaced by a sliding sleeve bearing. Basically replacing the ball/roller bearing with nothing. Some cost in friction but still no wear for the AP nanoscale system.

The macroscale system may critically need a bearing as just sliding friction under gravitational loads alone may be on a quickly self-destructive level. At least for FDM/FFF plastic 3D printed structures that can most certainly be the case. Author speaking from experience.

This is a disallowed vitamin from a RepRec local at home DIY self relicating pick-n-place robot though. So a slight conflict of interest here. Relating to the "neither fish nor fowl" topic section.

Related

• Applicability of macro 3D printing for nanomachine prototyping

External links

• https://en.wikipedia.org/wiki/Injection_moulding (de "Spritzgießen" translates to "injectioncasting")
• https://en.wikipedia.org/wiki/Die_casting (de "Druckguss" translates to "presscast")
• https://en.wikipedia.org/wiki/Compression_molding (de "Frompressen" translates to "shapepressing")