Stiffness
the less soft the nanomachinery the less imprecise the mechanosynthesis
Sufficient stiffness (more precisely: lattice scaled stiffness) is necessary …
- … for sufficient suppression of thermal vibration amplitudes.
- … to archive atomically precise positioning capability not just topological atomic precision
- … for making force applying mechanosynthesis possible
Also sufficient stiffness is …
- one reason for the choice of gemstone like compounds as good base material / far term target material
- an enabler for machine phase as a basis/enabler for fuhrer capabilities like …
- … dissipation sharing (an/the efficiency trick that soft molecular biology nanotechnology can't pull) and …
- … exothermy offloading (same)
Contents
[hide]Pathway perspectives
Direct path perspective:
Already starting out with high stiffness.
There are only some (but not none) stiffness challenges in the beginning.
The main challenge is rather becomes scaling up the essential system complexity many orders of magnitude.
See: Early diamondoid nanosystem pixel (direct path)
Incremental path perspective:
Gradually introducing sufficient stiffness into atomically precise structures
is of key importance for bootstrapping the far term goal of advanced nanofactories
through a series of earlier increasingly more powerful atomically precise productive nanosystems.
Amplitudes of thermally excited motions:
- First sufficiently below the size of pre-produced atomically precise blocks and self-alignment/self-centering slots.
- Later sufficiently below atom to atom distance to exponentially suppress misplacement errors.
Stiffness & mechanosynthesis
Two approaches to reduce misplacement error rates in mechanosynthesis:
- Higher stiffness of the structures for placement (kinematic loop, structure near tip apex)
=> exponential drop in error rates - Cooling locally the site of mechanosynthesis
=> linear drop in error rates, then nonlinear - eventual quantum freezout of phonon modes even
Related: Averting locally exoergic/exothermic reactions (this may not be that much of an issue, TBD)
Sufficient lattice scaled stiffness for early low stiffness systems
Usage of self assembled atomically precise base parts (aka "vitamins") allow for less stringent conditions on stiffness.
Only the lattice scaled stiffness must be sufficient for block based self centering assembly (which is not really callable "mechanosynthesis" yet).
(wiki-TODO: Add external link to lattice scaled stiffness explanation page - Eric Drexlers blog on internet archive.)
There's also: stiffness focusing / foldamer technology stiffness nesting
How stiffness scales with size
The scaling law for stiffness is such that smaller structures have lower stiffness ("softer").
See (with a big caveat below): Lower stiffness of smaller machinery
There's a better intuition for diamondoid nanomachinery than jelly!
Big caveat: This is actually quite misleading. What mostly matters instead is that
deflections from scale natural nanomachine motion frequencies
(assuming scale invariant constant speeds) stay the same.
See: Same relative deflections across scales
Or even drop with a bit due to some intentional slowdown for speeds at the nanoscale
Slowdown in speeds being compensated by higher throughput of smaller machinery!
Intentional slowdown to reduce (wearless) dynamic friction losses.
Trivia: Weird coincidence from Lower stiffness of smaller machinery:
Nanoscale diamond e.g. has a compliance that, when interpreted at the macroscale,
lies in a very intuitively understandable range.
See: The feel of atoms#Softness
Influence of stiffness on manipulator design
The choice of geometric design of nano-manipulators must be taken such
that the compliance of the material is compensated for.
Long skinny serial mechanics robotic arms (like many industry robots on the macroscale)
are a bad choice for the deep nanoscale. These will increase error rates in mechanosynthesis.
Bulky parallel mechanic manipulators are a good choice.
In advanced gem-gum factories this may be mostly an issue for
structures in building chambers doing mechanosynthesis.
I.e. mostly the very many highly specialized molecular mills in assembly level 1.
And some very few (much slower and much more inefficient) special general purpose post processing stations.
Note: Low temperatures (deep cryo) can help as a complementary factor.
I.e for low temperatures and decently stiff base structures
(excliding e.g. 3D structural DNA nanotechnology, including cryctolecule based stsructures)
somewhat filigree structures may work even at deep nanoscale.
Influence of stiffness on friction
More stiffness causes less or harder to excite degrees of freedom for thermal motion.
This allow for lower levels of friction.
See: Friction in gem-gum technology
Also to a particularly lack of stiffness related dissipation mechanism to investigate: Accidental heatpump
The limit to zero stiffness in early incremental path aka foldamer systems
Unfolded foldamers basically have zero stiffness (or rather the concept of stiffness breaks down) due to
their chains of single bonds allowing for quite unconstrained freedom of rotation.
They can attain stiffness when they fold up though by formation of internal bonds like
hydrogen bonds, dative bonds, Van der Waals bonds, and sometimes even covalent crosslinking bonds.
Some for this property optimized de-novo proteins can attain quite significant stiffness.
Structural DNA nanotechnology is an interesting case. Even after assembly locally there is practically zero stiffness. On a larger scale there is stiffness albeit quite low one.
Consequences of this include:
- Structural DNA nanotechnology features topological atomic precision but no positional atomic precision.
- Structural DNA nanotechnology can on it's own position something to positional atomic precision only over a time average.
- Structural DNA nanotechnology may be able to position something to positional atomic precision …
via Foldamer technology stiffness nesting/stiffness focusing i.e.
via integration of stiffer structural nanotechnologies
General
- The SI unit of (material specific) stiffness is newtons per square meter (N/m2 = Pa) (Young modulus tensor)
- The inverse of stiffness is called compliance. Not softness which would be the inverse of hardness.
- Unit of simple geometry specific stiffness is N/m (Hooks law applies)
Related
- The defining traits of gem-gum-tec
- Macroscale style machinery at the nanoscale
- Lattice scaled stiffness
- Mechanosynthesis
- Gemstone like compound
- High pressure
- Energy, force, and stiffness
- Lower stiffness of smaller machinery – an among experts known scaling law
- Same relative deflections across scales – an (even among experts) not well known scaling law
- Sloppy finger problem
External links
Related pages from
Eric Drexler's blog: Metamodern – The Trajectory of Technology
Recovered with the internet archives wayback machine.
(More recovered pages from this blog can be found here: Eric Drexler's blog partially dug up from the Internet Archive)
- Blogpost 2009-02-20: [1]
"Nanomachines, Nanomaterials, and Klm"
Subtitle: "Toward Advanced Nanotechnology: Nanomaterials (5)" - Blogpost 2009-02-15: [2].
"Nanostructures, Nanomaterials, and Lattice-Scaled Stiffness"
Subtitle: "Toward Advanced Nanotechnology: Nanomaterials (4)"
(Note: the uncrecovered direct link [3] works for this specific post BUT
many internal links are broken. Database damage presumably?)
Wikipedia
Some of the German pages seem better as of 2022:
- Stiffness – Steifigkeit
- Spring constant – Federkonstante
- Elastic modulus – Elastizitätsmodul
