From Wikipedia,
the free encyclopedia.
In
conventional chemical synthesis or
chemosynthesis, reactive
molecules encounter one another
through random thermal motion in a
liquid or vapor. In a hypothesized
process of mechanosynthesis,
reactive
molecules would be attached to
molecular mechanical systems, and
their encounters would result from
mechanical motions bringing them
together in planned sequences,
positions, and orientations. It is
envisioned that mechanosynthesis
would avoid unwanted reactions by
keeping potential reactants apart,
and would strongly favor desired
reactions by holding reactants
together in optimal orientations
for many molecular
vibration cycles.
Mechanosynthetic systems would be
designed to resemble some
biological mechanisms.
While the description of
mechanosynthesis given above has
not yet been achieved, primitve
mechanochemistry has been
performed at cryogenic
temperatures using
scanning tunneling scraping
electron microscopes). So far,
such devices provide the closest
approach to fabrication tools for
molecular engineering.
Broader exploitation of
mechanosynthesis awaits more
advanced technology for
constructing
molecular machine systems -
including a
molecular assembler or
precursors thereof.
It has been suggested, notably
by
K. Eric Drexler, that
mechanosynthesis will be
fundamental to
molecular manufacturing based
on
nanofactories capable of
building macroscopic objects with
atomic precision. The potential
for these has been disputed,
notably by
Nobel Laurate
Richard Smalley, leading to a
famous dispute between the two of
them - see
nanotechnology.
In part to resolve this and
related questions about the
dangers of
industrial accidents and
runaway events equivalent to
Chernobyl and
Bhopal, and the more remote
issue of
ecophagy,
grey goo and
green goo (various potential
disasters arising from runaway
replicators, which could be built
using mechanosynthesis) the
UK Royal Society and
UK Royal Academy of Engineering
in
2003 commissioned a study to
deal with these issues and larger
social and ecological
implications, led by
mechanical engineering
professor
Ann Dowling. This was
anticipated by some to take a
strong position on these problems
and potentials - and suggest any
development path to a general
theory of so-called
mechanosynthesis.
However, the
Royal Society's nanotech report
did not address molecular
manufacturing at all, except to
dismiss it along with gray goo.
Existing Work on Diamond
Mechanosynthesis
There is some peer-reviewed
research on synthesizing diamond
by mechanically depositing carbon
atoms (a process known as
mechanosynthesis).
For the paper by Mann, et al.,
the researchers used over 5 years
of CPU time to simulate a series
of "tool tips" which could be used
to place a pair of carbon atoms (a
dimer) onto a
diamond surface. The most
promising tip succeeded in placing
the carbon dimer onto the diamond
surface once in five simulations,
and it had to be positioned with
great accuracy to avoid bonding
the dimer incorrectly.
Furthermore, the tips were
difficult to recharge with a
second carbon dimer, and were only
stable in carefully controlled
environments.
Further research to consider
alternate tips will require
time-consuming
computational chemistry and
difficult laboratory work.
See also:
chemosynthesis
