
Drexler–Smalley debate on molecular nanotechnology - luu
https://en.wikipedia.org/wiki/Drexler%E2%80%93Smalley_debate_on_molecular_nanotechnology
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mannykannot
There is something ironic in Drexler's invocation of biology to defend the
plausibility of his vision, as it also suggests that biochemical and
biologically-inspired methods might well be more appropriate than his approach
of attempting to scale down human-scale machinery to a size where molecular
forces and quantum effects are significant. So far, it is the former, and only
the former, that has demonstrated progress.

Drexler's approach seems akin to building a computer by using micro-
fabrication techniques to create a network of tiny relays.

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vilhelm_s
A computer made of nanoscale mechanical latches, made using nano-fabricators,
was in fact one of the examples Drexler proposed. Supposedly it would perform
better than transistor-based ones.
[[http://www.halcyon.com/nanojbl/NanoConProc/nanocon2.html](http://www.halcyon.com/nanojbl/NanoConProc/nanocon2.html)]

But isn't current computers an example of microscale fabrication that worked
without being biochemical or biologically-inspired? They are made using
optical etching, completely different from anything biology does.

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mannykannot
> But isn't current computers an example of microscale fabrication that worked
> without being biochemical or biologically-inspired? They are made using
> optical etching, completely different from anything biology does.

Yes, and as such, this is another example suggesting that the road to nano-
technology is not through the shrinking of macro-scale machinery.

This may be moot, however, as this is not a self-replicating technology,
unlike either Drexler's hypothetical or biology's actual molecular assemblers.

Drexler's claims about the feasibility, let alone the performance, of his
proposed computer strike me as highly speculative and sometimes self-serving
(see, for example, the section on thermodynamic reversibility.) Furthermore,
computer performance has made huge advances since the devices (Z80, Motorola
68000) he was comparing to.

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williamjennings
Smalley was obviously right because Drexler thought that nanotechnology would
eventually become something like mechanical engineering. That does not work,
because quantum mechanics are the default nanoscale rules.

However, Drexler was able to contradict himself enough to make an interesting
point about molecular assembly in ribosomes; it just does not have the same
atomic precision as peptide synthesis. Therefore, nanotechnology is now firmly
in the discipline of chemical engineering.

In that article, I can find one quote from Smalley which was certainly untrue
at the time:

"biology is wonderous in the vast diversity of what it can build, but it can't
make a crystal of silicon, or steel, or copper, or aluminum, or titanium, or
virtually any of the key materials on which modern technology is built."

Shellfish nucleate crystals of silicon, and bacteria nucleate magnetic
nanoparticles of iron. That much was obvious to geologists during Smalley's
lifetime, but one could still construe chemical skepticism.

May the victor of the debate rest in peace; and let K. Eric Drexler correct
himself as much as he wants.

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murbard2
> Smalley was obviously right because Drexler thought that nanotechnology
> would eventually become something like mechanical engineering. That does not
> work, because quantum mechanics are the default nanoscale rules.

Non sequitur. First off, quantum mechanics apply at all scales, not just the
nanoscale. The question is whether one can model these those machines using
classical models instead of the much more computationally intensive quantum
mechanical models. Part of the reason the proposals focus on diamondoid
structures is that the rigidity of the bonds greatly limits the degrees of
freedoms, making molecular mechanics approach accurate enough to model various
designs.

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williamjennings
Talk about Non sequitur!

It does not seem like you understand my use of the word 'default'; because
scales are nested, the nanoscale is everywhere. One can design molecular
machines using classical models; but those models are chemical rather than
mechanical. The diamondoid structures are the fruit of carbon research; and
the molecular mechanics has gotten much computationally cheaper, especially
with regards to biomolecules. The motivation for using carbon is the
modularity, not rigidity; albeit biomolecules are even more modular than
carbon alone.

~~~
murbard2
The rigidity buys you a lot. It's not just easier modelling, it's also higher
reliability. If your bond is rigid, you don't have to worry too much about
heat causing errors in the synthesis.

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williamjennings
The rigidity is the expensive part. Modeling has gotten easier with parallel
distributed computing. Reliability is of qualia that I would only attribute to
platinum group metals. If heat causes errors in an organic synthesis, then
that reaction mechanism is not selective enough for the desired purpose. The
flexible bonds in biopolymers serve as counterpoint to the notion that bond
rigidity is essential to stochastic nanotechnology. On the contrary, self-
assembly requires some bond flexibility.

~~~
murbard2
Rigidity helps you for the same reason using a jointed arm is easier than
controlling a tentacle. Limiting the number of degrees of freedom can make
things a whole lot easier.

Yes, there are interesting designs with biopolymers, but they probably cannot
get you the type of atomically precise manufacturing that you need for most
"cool" MNT applications.

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williamjennings
It isn't fundamentally easier to control an arm than a tentacle; That is human
intuition based on the fact that we have arms. Limiting the number of degrees
of freedom is something done at the level of experimental design for the
production of chemical libraries. DNA is already a programmable medium for
nanorobotics, and skilled genetic engineers can do atomically precise peptide
biosynthesis for the sake of NMR spectroscopy. It does not seem as though you
are informed of bionanotechnology in the present.

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murbard2
Octopuses beg to differ
[http://www.ncbi.nlm.nih.gov/pubmed/16631583](http://www.ncbi.nlm.nih.gov/pubmed/16631583)

~~~
williamjennings
Octopodes do not beg to differ, they tergiversate to genuflect.

The thing to recognize is that tentacles predate arms, legs, or fins by
millennia. Jellyfish tentacles have fewer kinds of parts than any arm, hence
they constitute simpler machines.

In the paper you cite, humans are describing cephalopods with a model based on
their own anatomy; it is not the other way around, as you claim.

