Revision as of 14:55, 22 June 2023

Depicted: The (dated) concept of replicating diamondoid molecular assemblers. Here two free floating assemblers are in the process of copying themselves. Screencap from BBC Horizon doku "Nanoutopia" (1995)

Artistic depiction of a mobile assembler unit capable of self replication (linked to a "crystal" of assemblers and thus not free floating). An outdated idea.

Note: The concept of advanced molecular assemblers for diamondoid materials is outdated!
The current concept for advanced productive nanosystems of the "in-vacuum gem-gum technology" type are atomically precise small scale factories.

The three main problems with molecular assemblers are that they are:

• inefficient
• hard to reach
• undesirable

But molecular assemblers are:

• not fundamentally impossible

Molecular assemblers may emerge as esoteric products of advanced nanofactories (among other more useful "nanobots").
Molecular assemblers are member of the class of mobile nanoscale robotic devices ("nanobots") or even more generally Mobile robotic device.
It's important to be aware of these other nanobot (and microbot) concepts and not mix them up. Or give them new names in case concepts are mixed intentionally.

The idea

The idea is a machine which packages all the functionality to produce useful products and also make copies of itself (directly with diamondoid mechanosynthesis). This way one gets an exponential rate of replication and one can produce macroscopic goods in reasonable amounts of time.

Small size / ultra-comact self-replication

In the case of proto-assemblers these machines need to be very compact.
Due to the harsh limitations in scanning probe microscopy.
Typically suggested are one to a few hundred nanometers in side-lengths.

I the case of of molecular assemblers as advanced productive nanosystem (outdated) such limitations from scanning probe microscopy are absent though
a typical assumption is one active site for mechanosynthesis per assembler (and no convergent assembly) also posing harsh limits on assembler size for reasonable levels of throughput.

Overall molecular assemblers are highly compressed ultra compact replicators by definition.
Giving a very restricted and difficult design space.

Assembler hype hiding progress to nanofactoies

The assembler concept was a natural and obvious bioanalogy to introduce initially.
Continued refinement with exploratory engineering quickly led away from it though but this went almost unnoticed.
Initially no clear distinction was made between systems for bootstrapping and far term target systems as thee not yet was any deeper analysis.

The combination of their appearance (legs or other mechanisms to move about) with their very tightly packed capability of self replication in their vacuum "belly" that seem akin to a "whomb" was one factor in leading to the situation that the public started to perceive this technology as swarms of tiny life like nano-bugs that could potentially start uncontrollable and unstoppable self replication.

Why this is a rather miss-informed perception can be read up here and here.

• Dystopian SiFi fantasy anchored the idea of assemblers in the public perception (at least in USA and UK).
• Nanofactories coming close to the newer detailed concepts remain yet to be seen in fiction.

Partial design aspects of molecular assemblers that remain applicable

Many considerations about assemblers are still relevant:

• methods for movement e.g. for the transport of microcomponents and self repair by microcomponent replacement in the higher assembly levels of nanofactories. The legged block mobility design is also known from the concept of (speculative) utility fog but has other design priorities in a manufacturing context like more rigidity and less "intelligence".
• methods for gas tight sealing and locking parts out
• and many more ...
• the design of robotic mechanosyntesis cores

Old assembler designs

Quite a bit of thought was put into the assembler model (wiki-TODO: link relevant parts in KSRM). Either they where supposed to swim about in a solution or there was some form of movement mechanism in a machine phase scaffold crystal envisioned like:

• sliding cubes (wiki-TODO: TODO add references)
• legged blocks (wiki-TODO: TODO add references)

The ribosome and similar artificial biomimetic nano"machines"

These are also often called molecular assembler although they:

• are not capable of independent self replication
• are critically dependent on brownian motion / diffusion transport
• can only assembles floppy linear chain molecules which again need brownian motion to fold into something useful

Block placing assembler linkage

Unlike "diamondoid molecular assemblers" this idea is not outdated.
Atomically precise building blocks from structural DNA nanotechnology that are pre-produced by self assembly could be assembled to passive block manipulator linkages by those same passive block manipulator linkages after a first one was put together manually.
Actuation could be from a chips surface (see technology level I) and self replication could work in the form of exponential assembly.

• Crystolecule assembly robotics might become capable of more or less compact self replication with predelivered "vitamin" pasts from the mechanosynthesis cores.
• Wikipedia: Clanking replicator. A term to distinguish macroscale selfreplication from nanoscale selfreplication. But crystolecule level self replication is very similar to macroscale self replication. So the meaning can be dragged back. A clanking nano replicator so to say.
  (Sidenote: Actual clanking "sounds" should be avoided. Sound emission = loss of energy = inefficient operation = need for waste heat removal)

Possible exceptions

Occasions where somewhat molecular assembler like designs may not yet be completely outdated.

The only place where the slow and inefficient molecular assembler concept may be practically usable is for
self repair situations where the demand on product throughput rate is exceptionally low.
Like fixing low rates of damage from natural background radiation.
See: Self repairing system#In place self-repair

But even there a multi part system is more practical and likely.
So it would not operate alone but rather in conjunction with microcomponent maintenance units.

Microcomponent mainenance units ≠ Molecular assemblers

Main page: Microcomponent maintenance unit

Molecular assemblers are not to confuse with microcomponent maintenance units.
These are also relatively small and compact but they are incapable of mechanosynthesis.
More abstractly they have no manufacturing or demontage capabililities on the lowest assembly level.
Just like a microcomponent recomposer device.
But a microcomponent recomposer device is a macroscopic device whereas a microcomponent maintenance unit is a microscopic one.

Molecular assemblers in the technical book Nanosystems

There aren't any. They are not mentioned.
The closest thing to molecular assemblers in Nanosystems is Section 16.3.6. Minimal diamondoid-material systems and
it starts with: >>Any attempt to describe a "minimal" system must be considered speculative.<<

There is no proposal to build a diamondoid proto-system with a scanning probe tool (of macro- or microscale).
Scanning probe tools are only mentioned (subsection f. Summary.) as tools for analysis:
>>Molecilar probes can be used to determine the outcome of operations within a single device, ...<<

If anything this is rather meant as a later stage in the technical development ladder
that one likely will finds better/other solutions for (e.g. a less compact system).

Also there is no mention about mobility and free-floating non-mountedness.
A trait that is often ascribed to molecular assemblers and
a trait necessary for the grey goo scenario to sound plausible.

Related

• No nanobots
• Mobile robotic device
• Fractal growth speedup limit
• In place assembly and in place mechanosynthesis
• The better alternative that is now instead targeted: Gemstone metamaterial on chip factories
• Still quite compact but less compact self replication by adding one additional assembly level: Second assembly level self replication
  This would likely be a system of more or less mobile components on a surface or chip.

(wiki-TODO: add image of dividing cells illustrating the analogy - use it on other related pages too - goo)

• proto-assembler

• gemstone metamaterial on-chip factory – Identified as promising far term target via exploratory engineering

External links

• "Nanobots Not Needed" - March 2005