From: Crosby_M (Crosby_M@bls.gov)
Date: Thu Apr 24 1997 - 12:23:52 MDT
On Monday, April 21, 1997, Eugene Leitl forwarded a post that Anders
Sandberg made to sci.nanotech about nanodevices in regolith and how
these might be used to construct macro-scale devices such as
communication antennas. As Anders put it:
<Making the nanodevices build something macroscopic can probably be
done using chemical signals. A simple example could be that
assemblers are sensitive to the presence of waste products from other
assemblers, and tend to move away from them (increasing the spread
along the surface). One could implement many different chemical
signals such as "Assembler this way" (to make mining devices find the
assemblers) or "Build communications link" (produced by nanocomputers
with no links). This is the fun part, essentially what we need is a
system of chemical signals not unlike in an anthill combined with the
morphogenic chemicals used in early development to design the
macro-level structures. Any good ideas for suitable chemicals and
organisations of this system? >
Eugene subsequently forwarded a message from Ralph Merkle to the
Nanotechnology Study Group <NSG-d@world.std.com>, that suggested a few
URLs that might have been relevant to Anders' query.
However, a quick scan of Merkle's pages at Xerox didn't show anything
along the lines Anders was suggesting, just the orthodox
command-and-control nanotech approaches of 'positional control' and
'self-replication'. In fact, Merkle suggests (at
http://nano.xerox.com/nanotech/selfRep.html):
<The mechanical designs proposed for nanotechnology are more
reminiscent of a factory than of a living system. Molecular scale
robotic arms able to move and position molecular parts would assemble
rather rigid molecular products using methods more familiar to a
machine shop than the complex brew of chemicals found in a cell.
Although we are inspired by living systems, the actual designs are
likely to owe more to design constraints and our human objectives than
to living systems.>
In the same essay, Merkle later says:
<If artificial self replicating systems will only function in
carefully controlled artificial environments, how can we develop
applications of nanotechnology that function in complex environments,
such as the inside of the human body or a (rather messy) factory
floor? While self replicating systems are the key to low cost, there
is no need (and little desire) to have such systems function in the
outside world. Instead, in an artificial and controlled environment
they can manufacture simpler and more rugged systems that can then be
transferred to their final destination.>
Congratulations to Anders for coming up with a scenario that
challenges this approach.
More recently, Eugene posted >H FYI: NASA Explains How Molecular-Sized
Gears Might Work, a post by Bruce Mackenzie to the NSG forwarding a
NASA press release from those responsible for the NASA URL Merkle
mentioned:
<One practical use of nanotechnology would be to build a "matter
compiler," said Creon Levit, a Globus colleague at Ames. "We would
give this machine, made of nano parts, some raw materials, like
natural gas, for example. A computer program would specify an
arrangement of atoms, and the matter compiler would arrange the atoms
from the raw materials to make a macro-scale machine or parts," Levit
added.>
Later in this NASA press release, Globus is cited saying:
<"We would like to write computer programs that would enable
assembler/replicators to make aerospace materials, parts and machines
in atomic detail," he said. "Such materials should have tremendous
strength and thermal properties." Further information on these
materials can be obtained on the researchers' Internet page at URL:
http://www.nas.nasa.gov/nanotechnology. >
Well, I have to admit that I didn't take the time to look at these
NASA pages in any detail; but, somehow I doubt, from what the NASA
people have said above, that they have looked at the type of
approaches Anders was suggesting.
I don't want to restart the flame wars over whether 'positional
control' is practical for building macro-scale devices or not, and I
guess I'll just have to wait for Anders to finish his article, but I
would be very interested to know if he has found anyone working on the
chemical-signaling approach to nano-construction that he was
suggesting.
Mark Crosby
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