"One may now reasonably ask if it is possible to move and alter matter
predictably on an atomic scale we have evidence that we can remove
a portion of a pinned molecule, effectively performing transformations on
single molecules using the tunneling microscope," say John S. Foster,
Jane E. Frommer, and Patrick C. Arnett of IBM's
Almaden Research Center in a recent article in Nature.
The scanning tunneling microscope, as most of you know, is conceptually
quite simple. It uses a sharp, electrically-conductive needle to scan a
surface. The position of the tip of the needle is controlled to within 0.1
ångstrom (less than the radius of a hydrogen atom) using a voltage-controlled
piezo-electric drive. When the tip is within a few ångstroms of the
surface and a small voltage is applied to the needle, a tunneling current
flows from the tip to the surface. This tunneling current is then detected
and amplified, and can be used to map the shape of the surface, much as
a blind man's stick can reveal the shape of an object.
In the new work, the surface is atomically smooth graphite with a drop of
dimethyl phthalate (a liquid) on its surface. (The type of organic liquid
does not seem critical; many other compounds have been used.) The needle
is electrochemically etched tungsten, and is immersed in the liquid. Not
only can the graphite surface be imaged in the normal way, but a voltage
pulse applied to the needle (3.7 volts for 100 nanoseconds) can 'pin' one
of the organic molecules to the surface, where it can be viewed in the normal
fashion. A second voltage pulse applied at the same location can remove
the pinned molecule (though it often randomly pins other molecules in an
as-yet uncontrollable way). In some cases, the voltage pulse will remove
only part of the pinned molecule, leaving behind a molecularly altered fragment.
The first application that comes to mind is a very high density memory.
The minimum spot-size demonstrated in the new work is 10 ångstroms,
though a somewhat larger size might be required in practice. If we assume
that a single bit can be read or written into a 10 ångstrom square,
then a one square centimeter surface can hold 1014 bits. That's
one hundred terabytes. The 100 nanosecond pulse time sets a 10 megabit/second
maximum write rate, though this might be degraded for other reasons. At
this rate, it would take several months to a year of constant writing to
fill a one square centimeter memory. Access times will probably be limited
by the time needed to move the needle--which might be a significant fraction
of a second to travel one centimeter--giving access times similar to those
on current disk drives. The manufacturing cost of such a system is unclear,
but the basic components do not seem unduly expensive. It seems safe to
predict that someone in the not-too-distant future is going to build a low-cost
very large capacity secondary storage device (disk replacement)
based on this technology.
The larger implication of this work, however, is that it may put us on the
threshold of controlled molecular manipulation. While we can easily imagine
more powerful techniques than poking at objects with a sharpened stick (we
clearly want a pair of molecular-sized hands) the great virtue of this technique
is that we need not imagine it at all--it is real and is being pursued in
many laboratories. Even better, we can imagine incremental improvements
in this technique that ought to be achievable--using, perhaps, two
sharpened sticks (chopsticks, anyone?) and shaping the tip of the stick
in a more refined and controlled way. The tip, viewed at the atomic scale,
is rather rough and there seems no reason why we cannot do better--perhaps
by examining and modifying one stick with the other stick.
These larger implications have not been lost on the scientific community--in
an editorial on atomic-scale engineering in the same issue of Nature,
J. B. Pethica of the Oxford Department of Materials Science says that the
scanning tunneling microscope has " become one of the principle
gedanken tools for nanotechnology--the proposed direct manipulation
of matter, especially biological, on the atomic scale," and "The
work of Foster et al. represents a significant
attempt at the much more important and difficult problem of the direct manipulation
of the structure of biological materials."
Dr. Ralph Merkle's interests range from neurophysiology to computer security.
He currently works in the latter field at Xerox PARC.
"Molecular Manipulation using a Tunnelling
Microscope," by J. S. Foster, J. E. Frommer and P. C. Arnett; Nature,
Vol. 331, No. 28, 28 Jan. 1988, pp. 324-326.
"Atomic Scale Engineering," by J. B.
Pethica, op. cit. p. 301.
In a recent "Science Court" cover story in OMNI magazine,
writer Ed Regis asked prominent scientists to decide cases involving both
scientific or technological and ethical issues--the sorts of issues normally
decided by social norms, legislation, or a court of law. This mixing of
issues violates the most basic premise of the science court (SC) procedure,
developed by Arthur
Kantrowitz, which has as its ideal the separation of scientific and
technological questions from legal, ethical, and emotional ones.
The SC goal is not to permit scientists to make pronouncements on public
policy issues, but rather just the opposite: to enable society to extract
from expert communities their best available understanding of scientific
and technological facts, burdened by a minimum of personal opinion from
the technical people involved. This technical understanding could then be
used by legislators, judges, and other policymakers selected by society
in the usual ways. Proponents of the idea readily admit that perfect separation
of facts from values is not possible, but maintain that we as a society
could get a clearer understanding of technical realities by means of the
SC procedure than by means of media wars, secret committees, and congressional
The OMNI article features "decisions" from ten prominent
scientists including physicist Stephen Hawking, MIT's Seymour Papert, Edward
Teller, and computer scientist Joseph Weizenbaum. They were asked to make
legal or ethical pronouncements on surrogate motherhood, genetic engineering
in humans, alleged psychic powers, patenting genetically engineered animals,
and ownership of ancient human bones.
One scientist, the late Richard
Feynman, refused to participate on the excellent grounds that scientists
have no special ability to solve legal and ethical issues: "Suppose
I had one hundred percent access to the facts and one hundred percent knowledge
of the laws of nature. None of this would tell me whether a surrogate mother
should keep her baby or whether designer animals ought to be patented."
The other participants presumably were either unfamiliar with the original
SC concept or were unable to resist the temptation to mix their personal
ethical views with their scientific knowledge--a temptation the SC procedure
is designed to circumvent.
The SC is not a new proposal; it has been endorsed by various presidential
candidates in past elections. Originally seen as a function within government,
the idea has evolved into a procedure which could be used in a decentralized
way, for example at universities.
As stated by Arthur Kantrowitz (now a professor at Dartmouth) in his letter
of correction to OMNI, "There have been exercises at Berkeley
and Dartmouth which have helped in developing procedures. But the task is
difficult partially because some scientists prefer high priests' robes to
labcoats. Again some people prefer not having to stretch their minds enough
to deal with the moral and ethical problems posed by a science-based technology
which grows more and more powerful at an explosive rate. Those who would
control this force ... must get the scientific facts from the scientific
community. However, they must form their own moral and ethical judgments."
The confusion about the role of the science court is partly due to its name,
which was given to Dr. Kantrowitz's idea by the media. It implies a similarity
to a traditional court of law, which by its nature cannot confine itself
to matters of technical fact. The name gives the impression that the SC
could make public policy, just as today's courts of law effectively make
public policy by determining how laws are interpreted. Here at FI we substitute
the term "fact forum"; Dr. Kantrowitz now uses the term "scientific
Another problem the SC meme has faced is the difficulty of arranging in-person
meetings of busy technical people who, by definition, are adversaries on
some issue. FI believes that the establishment of hypertext publishing systems
will support online fact forum procedures. Meanwhile, existing software
such as DocuForum is being investigated; readers with suggestions on this
should contact FI.
For more on the SC/fact forum idea, see an account of the first three
trial SC procedures in a university setting, to be published by Roger Masters
and Arthur Kantrowitz in the upcoming book Technology and Politics
(ed. Michael Kraft and Norman Vig, Duke University, in press). A basic explanation
of the idea is available in Engines
of Creation (K. Eric Drexler, Doubleday, 1986).--Editor
When faced with something as novel as nanotechnology, it makes sense to
look for familiar analogies. Previous publications have compared nanomachines
to conventional macromachines, but in important ways nanomachines more closely
resemble software systems. Consider the properties of software and conventional
machines, then the parallels with assembler-built nanomachines.
Macromachines are made of parts which contain vast numbers of atoms in ill-defined
patterns. Having so many atoms, these parts can be made in what amounts
to a continuum of sizes and shapes, formed by continuous, analog techniques--molding,
cutting, grinding, etching, and so forth. These parts are always imprecise.
Machines are made by fitting parts together; in a good design, imprecisions
won't add up to exceed overall tolerances. In operation, parts typically
change shape slowly--they wear out and fail.
Software mechanisms differ radically. Their parts consist of discrete bits
in defined patterns--they do not form a continuum. There is no need to make
bits, as there is to make mechanical parts. The fabrication of bit-patterns
is a precise, digital process; it is either entirely correct or clearly
wrong, never "just a little off." The position of one bit with
respect to another is as precise as the mathematical position of "two"
with respect to "three."
The digital mechanisms which underlie this precision are made of imprecise
devices, but these devices have distinct patterns of interconnection and
distinct "on" and "off" states. Failures in the underlying
devices can cause sporadic errors in memory and logic, yet if the devices
operate within their design tolerances, errors (give or take an occasional
cosmic ray) will be completely absent. Digital precision emerges from imperfect
devices through a process like that of the automatic alignment found in
many computer graphics programs: a device in any state that is nearly-right
snaps into a neighboring state that is entirely-right. Each entirely-right
state follows from a previous entirely-right state, with no buildup of small
errors in, say, the size or alignment of the bits.
Nanomechanisms do have obvious similarities to conventional mechanisms.
Unlike software, they will be made of parts having size, shape, mass, strength,
stiffness, and so forth. They will often include gears, bearings, shafts,
casings, motors, and other familiar sorts of devices designed in accord
with familar principles of mechanical engineering. In most respects, nanomechanical
parts will resemble conventional parts, but made with far, far fewer atoms.
They will little resemble the algorithms and data structures of software.
And yet their similarity to software and digital mechanisms will be profound.
As software consists of discrete patterns of bits, so nanomechanisms will
consist of discrete patterns of atoms. Atoms, like bits, need not be made;
they are both flawless and available without need for manufacture. The parts
of nanomechanisms will not form a continuum of shapes, built by inaccurate
analog processes; they will instead be chosen from a discrete set of atom-patterns,
and (like bit patterns) these patterns will be either entirely correct or
clearly wrong. In stacking part on part there will be no buildup of small
errors, as there is in conventional systems.
As in digital circuits and computer graphics programs, a principle of automatic
alignment comes into play. When an assembler arm positions a reactive group
against a workpiece, forcing a reaction, imprecision of the arm's alignment
won't cause imprecision in the position of the added atoms. In making a
well-bonded object, molecular forces will snap the atoms either into the
proper position, or into a clearly wrong position. (As Marvin
Minsky remarks, quantum mechanics doesn't always make things more uncertain--quantum
states can be extraordinarily definite and precise.) Assembly can with high
reliability yield a perfect result.
And again like software, nanomechanisms won't wear out. So long as all the
atoms in a mechanism are present, properly bonded, and not in a distinct,
excited state, the mechanism is perfect. If an atom is missing or displaced
(say, by radiation damage) the mechanism isn't worn--it is broken.
In their shapes and functions, nanomechanisms will be much like ordinary
machines. But in their discreteness of structure and associated perfection--to
say nothing of their speed, accuracy, and replicability--nanomechanisms
will share some of the fundamental virtues of software.