Misleading aspects in animations of diamondoid molecular machine elements
There are at least two quite misleading artifacts stemming from
very high simulation speeds of ~100m/s to ~1km/s or so
(possibly even exceeding the ~3km/s of the unsupported rotating ring speed limit)
Why simulate so fast:
Simulations need to make the time-steps smaller than thermal atomic wiggles.
Reasonably slow nanomachinery speed would mean unreasonably many time-steps to compute.
Thus molecular dynamic simulations of nanomachinery is typically simulated at unreasonably high speeds.
Contents
[hide]No, nanoscale diamondoid (and gem based) parts are not floppy and jelly-like (at the nanoscale).
Misleading jelly like floppiness.
The jelly like flyoppyness visible in molecular dynamics simulations is a misleading artifact of the high speeds that these simulations require.
See also page: A better intuition for diamondoid nanomachinery than jelly
The intuition that we have for expectable degrees of
bending and deflections from motions in machines (at certain speeds) can be 1:1 directly applied from macroscale.
This is due to the lesser nown scaling law that relative deflections from motions are scale invariant.
See: Same relative deflections across scales
– Given the in this secific case (not generally of course!!) scale transferable intuition and
– given that at the nanoscale we have the following:
- material: solid diamond (or some similarly good gemstone) – all stiffer than steel
- proposed speeds: mere few mm/s – slower than macroscale robots
The expectable relative deflections from machine motions for nanoscale robotics are way below even
the expectable relative deflections from machine motions we see in macroscale metal robots (typically few m/s and below speeds).
A side-note on the proposed slower speeds for nanomachinery (nano mm/s, macro m/s)
deviating a bit form "same absolute speeds for smaller machinery":
- a reason is to reduce (werless) friction power losses
- it's toleable not huring throughput too much due to an other
lesser known important scaling law: higher throughput of smaller machinery
Macroscale analogy #1 – How macromachines would (quickly self selfsedting) run in corresponding conditions
Reversely running macroscale robotics at the extreme speeds the molecular dynamics simulations run
would make even spring steel parts flex just as much as the visible wobble in the simulations when slammed together.
Actually it would wobble with quite a bit larger amplitudes because spring steel
(or say nitinol that is ~10% superelastic bendable similar to flawless nanodiamond) is much less stiff than diamond.
Not to speak of horrendous wear that would occure at the nanoscale.
There are machines at the macroscale rrunning at near sonic or even supersonic speeds like the rotors in turbomolecular pupmps.
But these are magnetically levitated well balanced and non recirprocative.
We are talking about macines with reciprocative motions and physical contact bearings here.
(wiki-TODO: For illustration: Add a hyper slow-mo-cam image frame of jelly like ripples in normally not at all jelly considered matrial. "Smarter Every Day" has some nice ones IIRC.)
Macroscale analogy #2 – Intuitive experience constraint mapped to macroscale
Here's a contrived analogy example:
If one only ever saw spring steel colliding as colliding rods at hundreds of meters per second in videos
and never ever saw macroscale machines our of steel operating at "normal" machine speeds (meters per second or less),
then of course one would likely be mistaken in thinking that steel always behaves like floppy jelly
and one would quite likely mistakenly conclude that spring steel is an awfully jelly soft matrial
that would not at all make for good machines. Let's stick with stick & stone as we know that works.
This could be spun furter but I'll better stop here before overstretching the analogy too much.
Caveat: Thermal motions
This does not apply to thermally excited deformations.
Goes to show how violent these are at the nanoscale.
Structures must be thick enough to not flail around from thermal motions.
Accidental heatpump dissipation mechanism?
Terminology accident
The choice of the term gem-gum for gemstone based metamaterials and gem-gum technology
may be a bit unfortunate potentially corroborating a false intuition here.
The author (of this wiki) will keep it, but maybe more consciously use it.
No, machine motions are not near thermal motions (causing strong coupling and high losses).
See: Stroboscopic illusion in animations of diamondoid molecular machine elements
Actually even though here the effort might be taken to simulate very many timesteps,
showing just random snapshots instead of doing a proper motion blur leads to its own problems.
(wiki-TODO: Find and link a specific work on "multi stage motion blur" for molecular motions)
Exceptions
Assuming …
– Very sharply pulsed in time and/or …
– just one single nano-device active in an otherwise inactive macroscale heat-conductor
As may occur i some rare exotic situations,
then in this special case extreme speeds may quite likely actually be possible
with all the jelly wobbling and massive losses being a real thing to accept.
Trying near km/s operating speeds with macroscale machinery it would just self-destruct as
there is no way to run it in a short enough pulse or run it isolated enough.
It is "too much for itself" already.
Macroscale physics just has a too small a surface to volume ratio for cooling for that.
Related
- Stroboscopic illusion in animations of diamondoid molecular machine elements
- A better intuition for diamondoid nanomachinery than jelly
- Intercrystolecular snapping modes – Violent unconstrained spaps are one exception case where speeds and forces can become high enough to cause intermittent jelly like wobble. Just like a steel plate wobbles like jelly in slow motion footage when hit by a bullet, but here (nanoscale gemstome like materials) the materials survives with zero damage so long it gets sufficient cooling as is possible with snaps being either sparse in time or sparse in space (or both).
