I received the September issue of Scientific American today. This is
the special issue on nanotech, with some of the articles available
online at http://www.sciam.com/2001/0901issue/0901quicksummary.html.
Here are some excerpts from the article by Richard Smalley. Smalley is
a Nobel prize winning chemist (discoverer of buckminsterfullerene) and
nanotech researcher. The article does not really have anything new for
those who are familiar with Smalley's criticisms of nanotech.
Of Chemistry, Love and Nanobots
by Richard E. Smalley
How soon will we see the nanometer-scale robots envisaged by K. Eric
Drexler and other molecular nanotechnologists? The simple answer
In recent years, it has become popular to imagine tiny robots
(sometimes called assemblers) that can manipulate and build things
atom by atom. Imagine a single assembler: working furiously, this
hypothetical nanorobot would make many new bonds as it went about
its assigned task, placing perhaps up to a billion new atoms in the
desired structure every second.
But how realistic is this notion of a self-replicating nanobot?
Let's think about it. Atoms are tiny and move in a defined and
circumscribed way - a chemist would say that they move so as to
minimize the free energy of their local surroundings. The electronic
"glue" that sticks them to one another is not local to each bond but
rather is sensitive to the exact position and identity of all the
atoms in the near vicinity. So when the nanomanipulator arm of our
nanobot picks up an atom and goes to insert it in the desired place,
it has a fundamental problem. It also has to somehow control not only
this new atom but all the existing atoms in the region. No problem,
you say: our nanobot will have an additional manipulator arm for each
one of these atoms. Then it would have complete control of all the
goings-on that occur at the reaction site.
But remember, this region where the chemistry is to be controlled
by the nanobot is very, very small - about one nanometer on a side.
That constraint leads to at least two basic difficulties. I call
one the fat fingers problem and the other the sticky fingers problem.
Because the fingers of a manipulator arm must themselves be made out
of atoms, they have a certain irreducible size. There just isn't
enough room in the nanometer-size reactive region to accomodate
all the fingers of all the manipulators necessary to have complete
control of the chemistry. In a famous 1959 talk that has inspired
nanotechnologists everywhere, Nobel physicist Richard Feynman memorably
noted, "There's plenty of room at the bottom." But there's not *that*
Manipulator fingers on the hypothetical self-replicating nanobot
are not only too fat; they are also too sticky: the atoms of the
manipulator hands will adhere to the atom that is being moved. So it
will often be impossible to release this miniscule building block in
precisely the right spot.
Both these problems are fundamental, and neither can be avoided.
Self-replicating, mechanical nanobots are simply not possible in
our world. To put every atom in its place - the vision articulated
by some nanotechnologists - would require magic fingers. Such a
nanobot will never become more than a futurist's daydream.
This archive was generated by hypermail 2b30 : Fri Oct 12 2001 - 14:40:14 MDT