Incremental path

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Technology levels and steps of the incremental path
Level 0 side products
Introduction of total positional control xxx
Level I side products
switch-over to stiffer materials xxx
Level II side products
introduction of practically perfect vacuum xxx
Level III basis for products
advanced products
maybe-products

Up: Pathways to advanced APM systems

The incremental path towards advanced APM systems describes a desired process of slowly increasing technological capabilities (tools making better tools) with avoidance of loss of a strong orientation towards the far term goal of the stiff nanomachinery in gem-gum technology. This translates into starting off by using soft nanomachines to the fullest to get away from soft nanomachines ASAP.

The incremental path towards advanced APM systems is complementary to the direct path. The direct path to advanced APM systems in comparison describes a desired process of jumping to the advanced far term goal ASAP without significant detours. It is specifically focused on early usage of scanning probe microscopy for mechanosynthesis of diamond (or silicon) with throughput levels that are significant enough for the bootstrapping of a gem-gum factory. Following the direct path alone may be problematic.

  • Sometimes a direction that on first inspection looks like it would lead fast to the goal actually does lead to it very slowly (or even not at all).
  • Sometimes a direction that on first inspection looks as if it would lead only very slowly to the goal actually would lead to the goal fastest (which might still be slow).

This was the reason for the introduction of the distinction between direct path and incremental path.
Details on the critics towards the direct path will be located on the "direct path"-page.

High level map for the incremental path

Possible map for the incremental path.

This map here plots:

  • technology levels by use/control of material and means of assembly against ...
  • assembly levels as in the degree to which hierarchical selfassembly has been achieved.

The starting-point of technological development/progression is the bottom-most asterisk-star.
Green asterisks mark ares where some results have already been achieved.

The window of escape

The argument this map-diagram here is trying to justify is that there might be kind of a
window of escape between the blockades in pathways of development (red, orange, and yellow) .

Blockades:

  • The red, orange, and yellow stars tagged with "redundant" mean:
    Everything that positional assembly can do here selfassembly can do equally well (yellow) or better (red).
  • The red, orange, and yellow stars tagged with "too big to diffuse" means:
    Thermally driven selfassembly faces increasing problems due larger parts moving slower.

Starting out to the left right away is both

  • technically hardly possible (noncomposable primitive selfassemblies hardly can introduce positional assembly) and
  • economically not at all motivatable (due to the positional assembly redundancy blockade mentioned above)

Degree of directness of the indirect path

Note that there is kind of a degree of directness in the indirect path.
Directness in the sense of:

Depending on the directness of the indirect path further sub approaches of the indirect path can be identified:

Self-assembly – Climbing selfassembly levels

State of progress

A good place to look at is foldamer R&D specifically structural DNA nanotechnology.
Several noteworthy milestones have already been reached.

Metrics for progress

Bad metrics for progress (superficially impressive):

  • symmetry of self-assembles
  • size of self-assemblies

Good metrics for progress (more subtle):

Pushing against the limits of artificial self-assembly

What are the limitations to scaling up selfassembly?

  • (A) many blocks taking more time to find each other
  • (B) bigger blocks diffusing more slowly – The diffusion slowdown blockade
  • (C) limits in implementability of sets of complementary interfaces where correct pair bind well but wrong pairs do not
  • (D) wrong assembles not coming apart again – kinetic traps
  • ... and certainly more

Counterstrategies:

Base material – Climbing technology levels

The recently developed self assembling structural DNA nanotechnology and similar reliably designable foldamer structures might be a good starting point from technology level 0.

This very crude temporal outline is by no means the only possible way to go to eventually arrive at positional atomic precision.
There may be shortcuts or other paths. (See: Direct path)

Literature

In Appendix II of the book "Radical Abundance" [1] it is proposed to go through several levels of APM technology to reach advanced (positional atomic precision & diamondoid) APM. These levels will serve as a rough guideline for the structuring of this Wiki. In "Nanosystems" [2] technology stages are mentioned beginning with section 16.5.2. (written before the emergence of structural DNA nanotechnology).

Combining the best of different selfassembly technologies

Left: Adding small inserts that can be made stiffer in a lower stiffness background framework that can be made bigger. Right: Application of such a combining of self-assembly technologies technology demonstrated in the context of the foldamer printer concept.

Combining self assembly technologies could perhaps boost progress.
See main page: Combining advantages of different selfassembly technologies

Why positional control must be introduced before switchover to stiffest materials

For water synthesizable gemstone materials every crystal site looks exactly the same. Sites are featureless.
So to add atoms (or AP groups thereof) to such a crystal at desired locations (and there only),
the one single option available is positional assembly.
The same holds for materials made out of many identical small organic molecules.

Details:

... this is because stiffer materials cannot afford to encode the position of their constitute parts within the shape of their constitute parts which is what selfassembly mandates as fundamental prerequisite.
Such position in shape encoding forces a minimum size of constitute parts and bonds weak enough to be suitable for thermal annealing averting kinetic traps.

But what about Biomineralization?
Does it not work without positional assembly?

In biology biomineralization is likely not atomically precise. Bones & teeth (apatite or calcium-phosphate), shells (calcite or calcium-carbonate), diatoms (silica) all have no need to be atomically precise. Variously sized batches of phosphate, carbonate, silicate, sulfate, ions are probably just dumped in the general location to push the concentration locally to levels of where percipitation starts happening.
(TODO: verify lack of AP in biomineralization)

Yes, there is biomineral with atomic precision in the active center of some proteins, but this is usually just a few unit-cells.
The protein provides a one-off specialized solution for this exact nano-crystal.

Atomically precise positional control requires positional atomic precision

Attaining positional control mandates going from mere topological atomic precision (no errors in what links to what) to actual proper positional atomic precision (sub building block sized resolution – possibly subatomic resolution).

Weaker: Placing super-atomar blocks (small molecules, stiff compact de-novo-proteins) only requites block level precision.
See: Lattice scaled stiffness

Terminology

Since a nanofactory at the endpoint of an incremental path will inherit the capability of handling at least the materials of one generation before it,
it may be better to call the products gemoid instead of diamondoid this terminology would make it more clear that gemstone like bio-minerals like quartz are included.

Paths that are treated separately because its harder to find a concrete goal for them

Note that the behavior of mobile electrons at the nanoscale is not as easily predictable as the behavior of mechanics at the same scale thus there's less exploratory engineering for nanoelectronics than nanomechanics. See:

[Todo: improve article quality]

Terminology for early systems

In Erics blog (2018-11-10) early foldamer based systems were referred to as:
"modular molecular composite nanosystems (MMCNs)"
One could also perhaps call them:
"coarse-block atomically precise systems"

Related

External links

  • Slides: "Toward Modular Molecular Composite Nanosystems" -- K. Eric Drexler, PhD -- U.C. Berkeley -- 26 April 2009 -- [1]

References

  1. Radical Abundance: How a Revolution in Nanotechnology Will Change Civilization - by K. Eric Drexler
  2. Nanosystems: Molecular Machinery, Manufacturing, and Computation - by K. Eric Drexler