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Nanotech Scenario Series
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We present here an excerpt from
Unbounding the Future, by Eric Drexler and Chris Peterson, with Gayle
Pergamit...
Exploring the
Molecular World
In a scenario in the last chapter,
we saw Joel Gregory manipulating molecules in the virtual reality of a simulated
world using video goggles, tactile gloves, and a supercomputer. The early
twenty-first century should be able to do even better. Imagine, then, that today
you were to take a really long nap, oversleep, and wake up decades later in a
nanotechnological world.
In the twenty-first century, even
more than in the twentieth, it's easy to make things work without
understanding them, but to a newcomer much of the technology seems like magic,
which is dissatisfying. After a few days, you want to understand what
nanotechnology is, on a gut level. Back in the late twentieth century, most
teaching used dry words and simple pictures, but now—for a topic like
this—it's easier to explore a simulated world. And so you decide to explore a
simulation of the molecular world.
Looking through the brochure, you
read many tedious facts about the simulation: how accurate it is in describing
sizes, forces, motions, and the like; how similar it is to working tools used
by both engineering students and professionals; how you can buy one for your
very own home, and so forth. It explains how you can tour the human body, see
state-of-the-art nanotechnology in action, climb a bacterium, etc. For
starters, you decide to take an introductory tour: simulations of real
twentieth-century objects alongside quaint twentieth-century concepts of
nanotechnology.
After paying a small fee and
memorizing a few key phrases (any variation of "Get me out of here!" will do
the most important job), you pull on a powersuit, pocket a Talking Tourguide,
step into the simulation chamber, and strap the video goggles over your eyes.
Looking through the goggles, you seem to be in a room with a table you know
isn't really there and walls that seem too far away to fit in the simulation
chamber. But trickery with a treadmill floor makes the walk to the walls seem
far enough, and when you walk back and thump the table, it feels solid because
the powersuit stops your hand sharply at just the right place. You can even
feel the texture of the carvings on the table leg, because the suit's gloves
press against your fingertips in the right patterns as you move. The
simulation isn't perfect, but it's easy to ignore the defects. On the table is
(or seems to be) an old 1990s silicon computer chip. When you pick it up, as
the beginners' instructions suggest, it looks like Figure 1A. Then you say,
"Shrink me!", and the world seems to expand.
FIGURE 1: POWER OF TEN
Frame (A) shows a hand holding a computer chip. This is shown magnified
100 times in (B). Another factor of 100 magnification (C) shows a living
cell placed on the chip to show scale. Yet another factor of 100
magnification (D) shows two nanocomputers beside the cell. The smaller
(shown as block) has roughly the same power as the chip seen in the first
view; the larger (with only the corner visible) is as powerful as
mid-1980s mainframe computer. Another factor of 100 magnification (E)
shows an irregular protein from the cell on the lower right, and a
cylindrical gear made by molecular manufacturing at top left. Taking a
smaller factor of 10 jump, (F) shows two atoms in the protein, with
electron clouds represented by stippling. A final factor of 100
magnification (G) reveals the nucleus of the atom as a tiny speck.
Vision and
Motion
You feel as though you're falling
toward the chip's surface, shrinking rapidly. In a moment, it looks roughly
like Figure 1B, with your thumb still there holding it. The world grows
blurrier, then everything seems to go wrong as you approach the molecular
level. First, your vision blurs to uselessness—there is light, but it becomes
a featureless fog. Your skin is tickled by small impacts, then battered by
what feel like hard-thrown marbles. Your arms and legs feel as though they are
caught in turbulence, pulling to and fro, harder and harder. The ground hits
your feet, you stumble and stick to the ground like a fly on flypaper,
battered so hard that it almost hurts. You asked for realism, and only the
built-in safety limits in the suit keep the simulated thermal motions of air
molecules and of your own arms from beating you senseless.
"Stop!" gives you a rest from the
suit's yanking and thumping, and "Standard settings!" makes the world around
you become more reasonable. The simulation changes, introducing the standard
cheats. Your simulated eyes are now smaller than a light wave, making focus
impossible, but the goggles snap your vision into sharpness and show the atoms
around you as small spheres. (Real nanomachines are as blind as you were a
moment ago, and can't cheat.) You are on the surface of the 1990s computer
chip, between a cell and two blocky nanocomputers like the ones in Figure 1D.
Your simulated body is 50 nanometers tall, about 1/40,000,000 your real size,
and the smaller nanocomputer is twice your height. At that size, you can "see"
atoms and molecules, as in Figure 1E.
The simulation keeps bombarding
you with air molecules, but the standard settings leave out the sensation of
being pelted with marbles. A moment ago you were stuck tight to the ground by
molecular stickiness, but the standard settings give your muscles the
effective strength of steel—at least in simulation—by making everything around
you much softer and weaker. The tourguide says that the only unreal features
of the simulation have to do with you—not just your ability to see and
to ignore thermal shaking and bombardment, but also your sheer existence at a
size too small for anything so complex as a human being. It also explains why
you can see things move, something about slowing down everything around you by
a factor of 10 for every factor of 10 enlargement, and by another factor to
allow for your being made stronger and hence faster. And so, with your greater
strength and some adjustments to make your arms, legs, and torso less sticky,
you can stand, see, feel, and take stock of the situation.
Molecular
Texture
The ground underfoot, like
everything around you, is pebbly with atom-sized bumps the size of your
fingertips. Objects look like bunches of transparent grapes or fused marbles
in a variety of pretty but imaginary colors. The simulation displays a view of
atoms and molecules much like those used by chemists in the 1980s, but with a
sharper 3-D image and a better way to move them and to feel the forces they
exert. Actually, the whole simulation setup is nothing but an improved version
of systems built in the late 1980s—the computer is faster, but it is
calculating the same things. The video goggles are better and the whole-body
powersuit is a major change, but even in the 1980s there were 3-D displays for
molecules and crude devices that gave a sense of touching them.
The gloves on this suit give the
sensation of touching whatever the computer simulates. When you run a
fingertip over the side of the smaller nanocomputer, it feels odd, hard to
describe. It is as if the surface were magnetic—it pulls on your fingertip if
you move close enough. But the result isn't a sharp click of contact, because
the surface isn't hard like a magnet, but strangely soft. Touching the surface
is like touching a film of fog that grades smoothly into foam rubber, then
hard rubber, then steel, all within the thickness of a sheet of corrugated
cardboard. Moving sideways, your fingertip feels no texture, no friction, just
smooth bumps more slippery than oil, and a tendency to get pulled into
hollows. Pulling free of the surface takes a firm tug. The simulation makes
your atom-sized fingertips feel the same forces that an atom would. It is
strange how slippery the surface is—and it can't have been lubricated, since
even a single oil molecule would be a lump the size of your thumb. This
slipperiness makes it obvious how nano-scale bearings can work, how the parts
of molecular machines can slide smoothly.
But on top of this, there is a
tingling feeling in your fingers, like the sensation of touching a working
loudspeaker. When you put your ear against the wall of the nanocomputer, you
flinch back: for a moment, you heard a sound like the hiss of a
twentieth—century television tuned to a channel with no broadcast, with
nothing but snow and static—but loud, painfully loud. All the atoms in the
surface are vibrating at high frequencies, too fast to see. This is thermal
vibration, and it's obvious why it's also called thermal noise.
Gas and Liquid
Individual molecules still move
too quickly to see. So, to add one more cheat to the simulation, you issue the
command "Whoa!", and everything around seems to slow down by a factor of ten.
On the surface, you now can see
thermal vibrations that had been too quick to follow. All around, air
molecules become easier to watch. They whiz about as thick as raindrops in a
storm, but they are the size of marbles and bounce in all directions. They're
also sticky in a magnet-like way, and some are skidding around on the wall of
the nanocomputer. When you grab one, it slips away. Most are like two fused
spheres, but you spot one that is perfectly round—it is an argon atom, and
these are fairly rare. With a firm grip on all sides to keep it from shooting
away like a watermelon seed, you pinch it between your steel-strong fingers.
It compresses by about 10 percent before the resistance is more than you can
overcome. It springs back perfectly and instantly when you relax, then bounces
free of your grip. Atoms have an unfamiliar perfection about them, resilient
and unchanging, and they surround you in thick swarms.
At the base of the wall is a
churning blob that can only be a droplet of water. Scooping up a handful for a
closer look yields a swarm of molecules, hundreds, all tumbling and bumbling
over one another, but clinging in a coherent mass. As you watch, though, one
breaks free of the liquid and flies off into the freer chaos of the
surrounding air: the water is evaporating. Some slide up your arm and lodge in
the armpit, but eventually skitter away. Getting rid of all the water
molecules takes too much scraping, so you command "Clean me!" to dry off.
Too Small and
Too Large
Beside you, the smaller
nanocomputer is a block twice your height, but it's easy to climb up onto it
as the tourguide suggests. Gravity is less important on a small scale: even a
fly can defy gravity to walk on a ceiling, and an ant can lift what would be a
truck to us. At a simulated size of fifty nanometers, gravity counts for
nothing. Materials keep their strength, and are just as hard to bend or break,
but the weight of an object becomes negligible. Even without the
strength-enhancement that lets you overcome molecular stickiness, you could
lift an object with 40 million times your mass—like a person of normal size
lifting a box containing a half-dozen fully loaded oil tankers. To simulate
this weak gravity, the powersuit cradles your body's weight, making you feel
as if you were floating. This is almost like a vacation in an orbital theme
park, walking with stickyboots on walls, ceilings, and whatnot, but with no
need for anti-nausea medication.
On top of the nanocomputer is a
stray protein molecule, like the one in Figure 1E. This looks like a cluster
of grapes and is about the same size. It even feels a bit like a bunch of
grapes, soft and loose. The parts don't fly free like a gas or tumble and
wander like a liquid, but they do quiver like gelatin and sometimes flop or
twist. It is solid enough, but the folded structure is not as strong as your
steel fingers. In the 1990s, people began to build molecular machinery out of
proteins, copying biology. It worked, but it's easy to see why they moved on
to better materials.
From a simulated pocket, you pull
out a simulated magnifying glass and look at the simulated protein. This shows
a pair of bonded atoms on the surface at 10 times magnification, looking like
Figure 1F. The atoms are almost transparent, but even a close look doesn't
reveal a nucleus inside, because it's too small to see. It would take 1,000
times magnification to be able to see it, even with the head start of being
able to see atoms with your naked eye. How could people ever confuse big,
plump atoms with tiny specks like nuclei? Remembering how your steel-strong
fingers couldn't press more than a fraction of the way toward the nucleus of
an argon atom from the air, it's clear why nuclear fusion is so difficult. In
fact, the tourguide said that it would take a real-world projectile over a
hundred times faster than a high-powered rifle bullet to penetrate into the
atomic core and let two nuclei fuse. Try as you might, there just isn't
anything you could find in the molecular world that could reach into the
middle of an atom to meddle with its nucleus. You can't touch it and you can't
see it, so you stop squinting though the magnifying glass. Nuclei just aren't
of much interest in nanotechnology.
Puzzle Chains
Taking the advice of the
tourguide, you grab two molecular knobs on the protein and pull. It resists
for a moment, but then a loop comes free, letting other loops flop around
more, and the whole structure seems to melt into a writhing coil. After a bit
of pulling and wrestling, the protein's structure becomes obvious: It is a
long chain—longer than you are tall, if you could get it straight—and each
segment of the chain has one of several kinds of knobs sticking off to the
side. With the multicolored, glassy-bead portrayal of atoms, the protein chain
resembles a flamboyant necklace. This may be decorative, but how does it all
go back together? The chain flops and twists and thrashes, and you pull and
push and twist, but the original tight, solid packing is lost. There are more
ways to go wrong in folding up the chain than there are in solving Rubik's
Cube, and now that the folded structure is gone, it isn't even clear what the
result should look like. How did those twentieth-century researchers ever
solve the notorious "protein folding problem"? It's a matter of record that
they started building protein objects in the late 1980s.
This protein molecule won't go
back together, so you try to break it. A firm grip and a powerful yank
straightens a section a bit, but the chain holds together and snaps back.
Though unfolding it was easy, even muscles with the strength of steel—the
strength of Superman—can't break the chain itself. Chemical bonds are
amazingly strong, so it's time to cheat again. When you say, "Flimsy world—one
second!" while pulling, your hands easily move apart, splitting the chain in
two before its strength returns to normal. You've forced a chemical change,
but there must be easier ways since chemists do their work without tiny
superhands. While you compare the broken ends, they thrash around and bump
together. The third time this happens, the chain rejoins, as strong as before.
This is like having snap-together parts, but the snaps are far stronger than
welded steel. Modern assembler chemistry usually uses other approaches, but
seeing this happen makes the idea of molecular assembly more understandable:
Put the right pieces together in the right positions, and they snap together
to make a bigger structure.
Remembering the "Whoa!" command,
you decide to go back to the properly scaled speed for your size and strength.
Saying "Standard settings!," you see the thrashing of the protein chain speed
up to hard-to-follow blur.
Nanomachines
At your feet is a ribbed, ringed
cylindrical object about the size of a soup can—not a messy, loosely folded
strand like the protein (before it fell apart), but a solid piece of modern
nanotechnology. It's a gear like the one in Figure 1E. Picking it up, you can
immediately feel how different it is from a protein. In the gear,
everything is held in place by bonds as strong as those that strung
together the beads of the protein chain. It can't unfold, and you'd have to
cheat again to break its perfect symmetry. Like those in the wall of the
nanocomputer, its solidly attached atoms vibrate only slightly. There's
another gear nearby, so you fit them together and make the atomic teeth mesh,
with bumps on one fitting into hollows on the other. They stick together, and
the soft, slick atomic surfaces let them roll smoothly.
Underfoot is the nanocomputer
itself, a huge mechanism built in the same rigid style. Climbing down from it,
you can see through the transparent layers of the wall to watch the inner
works. An electric motor an arm-span wide spins inside, turning a crank that
drives a set of oscillating rods, which in turn drive smaller rods. This
doesn't look like a computer; it looks more like an engineer's fantasy from
the nineteenth century. But then, it is an antique design–the tourguide said
that the original proposal was a piece of exploratory engineering dating from
the mid-1980s, a mechanical design that was superseded by improved electronic
designs before anyone had the tools to build even a prototype. This simulation
is based on a version built by a hobbyist many years later.
The mechanical nanocomputer may
be crude, but it does work, and it's a lot smaller and more efficient than the
electronic computers of the early 1990s. It's even somewhat faster. The rods
slide back and forth in a blur of motion, blocking and unblocking each other
in changing patterns, weaving patterns of logic. This nanocomputer is a
stripped-down model with almost no memory, useless by itself. Looking beyond
it, you see the other block—the one on the left in Figure 1D—which contains a
machine powerful enough to compete with most computers built in 1990. This
computer is a millionth of a meter on a side, but from where you stand, it
looks like a blocky building looming over ten stories tall. The tourguide says
that it contains over 100 billion atoms and stores as much data as a room full
of books. You can see some of the storage system inside: row upon row of racks
containing spools of molecular tape somewhat like the protein chain, but with
simple bumps representing the 1s and 0s of computer data.
These nanocomputers seem big and
crude, but the ground you're now standing on is also a computer—a single chip
from 1990, roughly as powerful as the smaller, stripped-down nanocomputer at
your side. As you gaze out over the chip, you get a better sense for just how
crude things were a few decades ago. At your feet, on the smallest scale, the
chip is an irregular mess. Although the wall of the nanocomputer is pebbly
with atomic-scale bumps, the bumps are as regular as tile. The chip's surface,
though, is a jumble of lumps and mounds. This pattern spreads for dozens of
paces in all directions, ending in an irregular cliff marking the edge of a
single transistor. Beyond, you can see other ridges and plateaus stretching
off to the horizon. These form grand, regular patterns, the circuits of the
computer. The horizon—the edge of the chip—is so distant that walking there
from the center would (as the tourguide warns) take days. And these
vast pieces of landscaping were considered twentieth-century miracles of
miniaturization?
Cells and
Bodies
Even back then, research in
molecular biology had revealed the existence of smaller, more perfect machines
such as the protein molecules in cells. A simulated human cell–put here
because earlier visitors wanted to see the size comparisons—its on the chip
next to the smaller nanocomputer. The tourguide points out that the simulation
cheats a bit at this point, making the cell act as though it were in a watery
environment instead of air. The cell dwarfs the nanocomputer, sprawling across
the chip surface and rearing into the sky like a small mountain. Walking the
nature trail around its edge would lead across many transistor-plateaus and
take about an hour. A glance is enough to show how different it is from a
nanocomputer or a gear: it looks organic, it bulges and curves like a
blob of liver, but its surface is shaggy with waving molecular chains.
Walking up to its edge, you can
see that the membrane wrapping the cell is fluid (cell walls are for
stiff things like plants), and the membrane molecules are in constant motion.
On an impulse, you thrust your arm through the membrane and poke around
inside. You can feel many proteins bumping and tumbling around in the cell's
interior fluid, and a crisscrossing network of protein cables and beams.
Somewhere inside are the molecular machines that made all these proteins, but
such bits of machinery are embedded in a roiling, organic mass. When you pull
your arm out, the membrane flows closed behind. The fluid, dynamic structure
of the cell is largely self healing. That's what let scientists perform
experimental surgery on cells with the old, crude tools of the twentieth
century: They didn't need to stitch up the holes they made when they poked
around inside.
Even a single human cell is huge
and complex. No real thinking being could be as small as you are in the
simulation: A simple computer without any memory is twice your height, and the
larger nanocomputer, the size of an apartment complex, is no smarter than one
of the submoronic computers of 1990. Not even a bendable finger could be as
small as your simulated fingers: in the simulation, your fingers are only one
atom wide, leaving no room for the slimmest possible tendon, to say nothing of
nerves.
For a last look at the organic
world, you gaze out past the horizon and see the image of your own, full-sized
thumb holding the chip on which you stand. The bulge of your thumb rises ten
times higher than Mount Everest. Above, filling the sky, is a face looming
like the Earth seen from orbit, gazing down. It is your own face, with cheeks
the size of continents. The eyes are motionless. Thinking of the tourguide's
data, you remember: the simulation uses the standard mechanical scaling rules,
so being 40 million times smaller has made you 40 million times faster. To let
you pull free of surfaces, it increased your strength by more than a factor of
100, which increased your speed by more than a factor of 10. So one second in
the ordinary world corresponds to over 400 million here in the simulation. It
would take years to see that huge face in the sky complete a single eyeblink.
Enough. At the command "Get me
out!", the molecular world vanishes, and your feeling of weight returns as the
suit goes slack. You strip off the video goggles—and hugely, slowly, blink.
The Silicon Valley Faire
The tour of the molecular world showed some
products of molecular manufacturing, but didn't show how they were made. The
technologies you remember from the old days have mostly been replaced—but how
did this happen? The Silicon Valley Faire is advertised as "An authentic theme
park capturing life, work, and play in the early Breakthrough years." Since
"work" must include manufacturing, it seems worth a visit.
A broad dome caps the park — "To fully capture
the authentic sights, sounds, and smells of the era," the tourguide politely
says. Inside, the clothes and hairstyles, the newspaper headlines, the
bumper-to-bumper traffic, all look much as they did before your long nap. A
light haze obscures the buildings on the far side of the dome, your eyes burn
slightly, and the air smells truly authentic.
The Nanofabricators, Inc., plant offers the
main display of early nanotechnology. As you near the building, the tourguide
mentions that this is indeed the original manufacturing plant, given landmark
status over twenty years ago, then made the centerpiece of the Silicon Valley
Faire ten years later, when . . . With a few taps, you reset the pocket
tourguide to speak up less often.
Pocket Libraries
As people file into the Nanofabricator plant,
there's a moment of hushed quiet, a sense of walking into history.
Nanofabricators: home of the SuperChip, the first mass-market product of
nanotechnology. It was the huge memory capacity of SuperChips that made
possible the first Pocket Library.
This section of the plant now houses a series of displays, including working
replicas of early products. Picking up a Pocket Library, you find that it's
not only the size of a wallet, but about the same weight. Yet it has enough
memory to record every volume in the Library of Congress—something like a
million times the capacity of a personal computer from 1990. It opens with a
flip, the two-panel screen lights up, and a world of written knowledge is at
your fingertips. Impressive.
"Wow, can you believe these things?" says another tourist as he fingers a
Pocket Library. "Hardly any video, no 3-D–just words, sound, and flat
pictures. And the cost! I wouldn't have bought `em for my kids at that
price!"
Your tourguide quietly states the price: about what you remember for a
top-of-the-line TV set from 1990. This isn't the cheap manufacturing promised
by mature nanotechnology, but it seems like a pretty good price for a library.
Hmm . . . how did they work out the copyrights and royalties? There's a lot
more to this product than just the technology . . .
Nanofabrication
The next room displays more technology. Here
in the workroom where SuperChips were first made, early nanotech manufacturing
is spread out on display. The whole setup is surprisingly quiet and ordinary.
Back in the 1980s and 1990s, chip plants had carefully controlled clean rooms
with gowns and masks on workers and visitors, special workstations, and
carefully crafted air flows to keep dust away from products. This room has
none of that. It's even a little grubby.
In the middle of a big square table are a half-dozen steel tanks, about the
size and shape of old-fashioned milk cans. Each can has a different label
identifying its contents: MEMORY BLOCKS, DATA-TRANSMISSION BLOCKS, INTERFACE
BLOCKS. These are the parts needed for building up the chip. Clear plastic
tubes, carrying clear and tea-colored liquids, emerge from the mouths of the
milk cans and drape across the table. The tubes end in fist-sized boxes
mounted above shallow dishes sitting in a ring around the cans. As the
different liquids drip into each dish, a beater like a kitchen mixer swirls
the liquid. In each dish, nanomachines are building SuperChips.
A Nanofab "engineer," dressed in period clothing complete with name badge, is
setting up a dish to begin building a new chip. "This," he says, holding up a
blank with a pair of tweezers, "is a silicon chip like the ones made with
pre-breakthrough technology. Companies here in this valley made chips like
these by melting silicon, freezing it into lumps, sawing the lumps into
slices, polishing the slices, and then going through a long series of chemical
and photographic steps. When they were done, they had a pattern of lines and
blobs of different materials on the surface. Even the smallest of these blobs
contained billions of atoms, and it took several blobs working together
to store a single bit of information. A chip this size, the size of your
fingernail, could store only a fraction of a billion bits. Here at Nanofab, we
used bare silicon chips as a base for building up nanomemory. The picture on
the wall here shows the surface of a blank chip: no transistors, no memory
circuits, just fine wires to connect up with the nanomemory we built on top.
The nanomemory, even in the early days, stored thousands of billions of
bits. And we made them like this, but a thousand at a time–" He places the
chip in the dish, presses a button, and the dish begins to fill with liquid.
"A few years latter," he adds, "we got rid of the silicon chips entirely"—he
props up a sign saying THIS CHIP BUILD BEGAN AT: 2:15 P.M., ESTIMATED
COMPLETION TIME: 1:00 A.M.—" and we sped up the construction process by a
factor of a thousand."
The chips in the dishes all look pretty much the same except for color. The
new chip looks like dull metal. The only difference you can see in the older
chips, further along in the process, is a smooth rectangular patch covered by
a film of darker material. An animated flowchart on the wall shows how layer
upon layer of nanomemory building blocks are grabbed from solution and laid
down on the surface to make that film. The tourguide explains that the energy
for this process, like the energy for molecular machines within cells, comes
from dissolved chemicals—from oxygen and fuel molecules. The total amount of
energy needed here is trivial, because the amount of product is trivial: at
the end of the process, the total thickness of nanomemory structure—the memory
store for a Pocket Library—amounts to one-tenth the thickness of a sheet of
paper, spread over an area smaller than a postage stamp.
Molecular Assembly
The animated flowchart showed nanomemory
building blocks as big things containing about a hundred thousand atoms apiece
(it takes a moment to remember that this is still submicroscopic). The build
process in the dishes stacked these blocks to make the memory film on the
SuperChip, but how were the blocks themselves built? The hard part in this
molecular-manufacturing business has got to be at the bottom of the whole
process, at the stage where molecules are put together to make large, complex
parts.
The Silicon Valley Faire offers simulations of this molecular assembly
process, and at no extra charge. From the tourguide, you learn that modern
assembly processes are complex; that earlier processes—like those used by
Nanofabricators, Inc.—used clever-but-obscure engineering tricks; and that the
simplest, earliest concepts were never built. Why not begin at the beginning?
A short walk takes you to the Museum of Antique Concepts, the first wing of
the Museum of Molecular Manufacturing.
A peek inside the first hall shows several people strolling around wearing
loosely fitting jumpsuits with attached goggles and gloves, staring at nothing
and playing mime with invisible objects. Oh well, why not join the fools'
parade? Stepping through the doorway while wearing the suit is entirely
different. The goggles show a normal world outside the door and a molecular
world inside. Now you, too, can see and feel the exhibit that fills the hall.
It's much like the earlier simulated molecular world: it shares the standard
settings for size, strength, and speed. Again, atoms seem 40 million times
larger, about the size of your fingertips. This simulation is a bit less
thorough than the last was—you can feel simulated objects, but only with your
gloved hands. Again, everything seems to be made of quivering masses of fused
marbles, each an atom.
"Welcome," says the tourguide, "to a 1990 concept for a
molecular-manufacturing plant. These exploratory engineering designs were
never intended for actual use, yet they demonstrate the basics of molecular
manufacturing: making parts, testing them, and assembling them."
Machinery fills the hall. Overall, the sight is reminiscent of an automated
factory of the 1980s or 1990s. It seems clear enough what must be going on:
Big machines stand beside a conveyor belt loaded with half-finished-looking
blocks of some material (this setup looks much like Figure 2); the machines
must do some sort of work on the blocks. Judging by the conveyor belt, the
blocks eventually move from one arm to the next until they turn a corner and
enter the next hall.
FIGURE 2: ASSEMBLER
WITH FACTORY ON CHIP
A
factory large enough to make over 10 million nanocomputers per day would fit
on the edge one of today's integrated circuits. Inset shows an assembler arm
together with workpiece on a conveyor belt.
Since nothing is real, the exhibit can't be damaged, so you walk up to a
machine and give it a poke. It seems as solid as the wall of the nanocomputer
in the previous tour. Suddenly, you notice something odd: no bombarding air
molecules and no droplets of water—in fact, no loose molecules anywhere. Every
atom seems to be part of a mechanical system, quivering thermal vibration, but
otherwise perfectly controlled. Everything here is like the nanocomputer or
like the tough little gear; none of it resembles the loosely coiled protein or
the roiling mass of the living cell.
The conveyor belt seems motionless. At regular intervals along the belt are
blocks of material under construction: workpieces. The nearest block is about
a hundred marble-bumps wide, so it must contain something like 100 x 100 x 100
atoms, a full million. This block looks strangely familiar, with its rods,
crank, and the rest. It's a nanocomputer—or rather, a block-like part of a
nanocomputer still under construction.
Standing alongside the pieces of nanocomputer on the conveyor belt, dominating
the hall, is a row of huge mechanisms. Their trunks rise from the floor, as
thick as old oaks. Even though they bend over, they rear overhead. "Each
machine," your tourguide says, "is the arm of a general-purpose molecular
assembler.
One assembler arm is bent over with its tip pressed to a block on the conveyor
belt. Walking closer, you see molecular assembly in action. The arm ends in a
fist-sized knob with a few protruding marbles, like knuckles. Right now, two
quivering marbles—atoms—are pressed into a small hollow in the block. As you
watch, the two spheres shift, snapping into place in the block with a quick
twitch of motion: a chemical reaction. The assembler arm just stands there,
nearly motionless. The fist has lost two knuckles, and the block of
nanocomputer is two atoms larger.
The tourguide holds forth: "This general-purpose assembler concept resembles,
in essence, the factory robots of the 1980s. It is a computer-controlled
mechanical arm that moves molecular tools according to a series of
instructions. Each tool is like a single-shot stapler or rivet gun. It has a
handle for the assembler to grab and comes loaded with a little bit of
matter—a few atoms—which it attaches to the workpiece by a chemical reaction."
This is like the rejoining of the protein chain in the earlier tour.
Molecular Precision
The atoms seemed to jump into place easily
enough; can they jump out of place just as easily? By now the assembler arm
has crept back from the surface, leaving a small gap, so you can reach in and
poke at the newly added atoms. Poking and prying do no good; when you push as
hard as you can (with your simulated fingers as strong as steel), the atoms
don't budge by a visible amount. Strong molecular bonds hold them in place.
Your pocket tourguide—which has been applying the power of a thousand 1990s
supercomputers to the task of deciding when to speak up—remarks, "Molecular
bonds hold things together. In strong, stable materials atoms are either
bonded, or they aren't, with no possibilities in between. Assemblers work by
making and breaking bonds, so each step either succeeds perfectly or fails
completely. In pre-breakthrough manufacturing, parts were always made and put
together with small inaccuracies. These could add up to wreck product quality.
At the molecular scale, these problems vanish. Since each step is perfectly
precise, little errors can't add up. The process either works, or it doesn't."
But what about those definite, complete failures? Fired by scientific
curiosity, you walk to the next assembler, grab the tip, and shake it. Almost
nothing happens. When you shove as hard as you can, the tip moves by about
one-tenth of an atomic diameter, then springs back. "Thermal vibrations can
cause mistakes by causing parts to come together and form bonds in the wrong
place," the tourguide remarks. "Thermal vibrations make floppy objects bend
further than stiff ones, and so these assembler arms were designed to be thick
and stubby to make them very stiff. Error rates can be kept to one in a
trillion, and so small products can be perfectly regular and perfectly
identical. Large products can be almost perfect, having just a few
atoms out of place." This should mean high reliability. Oddly, most of the
things you've been seeing outside have looked pretty ordinary—not slick,
shiny, and perfect, but rough and homey. They must have been manufactured
that way, or made by hand. Slick, shiny things must not impress anyone
anymore.
Molecular Robotics
By now, the assembler arm has moved by several
atom-widths. Through the translucent sides of the arm you can see that the arm
is full of mechanisms: twirling shafts, gears, and large, slowly turning rings
that drive the rotation and extension of joints along the trunk. The whole
system is a huge, articulated robot arm. The arm is big because the smallest
parts are the size of marbles, and the machinery inside that makes it move and
bend has many, many parts. Inside, another mechanism is at work: The arm now
ends in a hole, and you can see the old, spent molecular tool being retracted
through a tube down the middle.
Patience, patience. Within a few minutes, a new tool is on its way back up the
tube. Eventually, it reaches the end. Shafts twirl, gears turn, and clamps
lock the tool in position. Other shafts twirl, and the arm slowly leans up
against the workpiece again at a new site. Finally, with a twitch of motion,
more atoms jump across, and the block is again just a little bit bigger. The
cycle begins again. This huge arm seems amazingly slow, but the standard
simulation settings have shifted speeds by a factor of over 400 million. A few
minutes of simulation time correspond to less than a millionth of a second of
real time, so this stiff, sluggish arm is completing about a million
operations per second.
Peering down at the very base of the assembler arm, you can get a glimpse of
yet more assembler-arm machinery underneath the floor: Electric motors spin,
and a nanocomputer chugs away, rods pumping furiously. All these rods and
gears move quickly, sliding and turning many times for every cycle of the
ponderous arm. This seems inefficient; the mechanical vibrations must generate
a lot of heat, so the electric motors must draw a lot of power. Having a
computer control each arm is a lot more awkward now than it was in
pre-breakthrough years. Back then, a robot arm was big and expensive and a
computer was a cheap chip; now the computer is bigger than the arm. There must
be a better way—but then, this is the Museum of Antique Concepts.
Building-Blocks into
Buildings
Where do the blocks go, once the assemblers
have finished with them? Following the conveyor belt past a dozen arms, you
stroll to the end of the hall, turn the corner, and find yourself on a balcony
overlooking a vaster hall beyond. Here, just off the conveyor belt, a block
sits in a complex fixture. Its parts are moving, and an enormous arm looms
over it like a construction crane. After a moment, the tourguide speaks up and
confirms your suspicion: "After manufacturing, each block is tested. Large
arms pick up properly made blocks. In this hall, the larger arms assemble
almost a thousand blocks of various kinds to make a complete nanocomputer.
The grand hall has its own conveyor belt, bearing a series of partially
completed nanocomputers. Arrayed along this grand belt is a row of grand arms,
able to swing to and fro, to reach down to lesser conveyor belts, pluck
million-atom blocks from testing stations, and plug them into the grand
workpieces, the nanocomputers under construction. The belt runs the length of
the hall, and at the end, finished nanocomputers turn a corner—to a
yet-grander hall beyond?
After gazing at the final-assembly hall for several minutes, you notice that
nothing seems to have moved. Mere patience won't do: at the rate the smaller
arms moved in the hall behind you, each block must take months to complete,
and the grand block-handling arms are taking full advantage of the leisure
this provides. Building a computer, start to finish, might take a terribly
long time. Perhaps as long as the blink of an eye.
Molecular assemblers build blocks that go to block assemblers. The block
assemblers build computers, which go to system assemblers, which build
systems, which–at least one path from molecules to large products seems clear
enough. If a car were assembled by normal-sized robots from a thousand pieces,
each piece having been assembled by smaller robots from a thousand smaller
pieces, and so on, down and down, then only ten levels of assembly process
would separate cars from molecules. Perhaps, around a few more corners and
down a few more ever-larger halls, you would see a post-breakthrough car in
the making, with unrecognizable engine parts and comfortable seating being
snapped together in a century-long process in a hall so vast that the Pacific
Ocean would be a puddle in the corner . . .
Just ten steps in size; eight, starting with blocks as big as the ones made in
the hall behind you. The molecular world seems closer, viewed this way.
Molecular Processing
Stepping back into that hall, you wonder how
the process begins. In every cycle of their sluggish motion, each molecular
assembler gets a fresh tool through a tube from somewhere beneath the floor,
and that somewhere is where the story of molecular precision begins.
And so you ask, "Where do the tools come from?", and the tourguide replies,
"You might want to take the elevator to your left."
Stepping out of the elevator and into the basement, you see a wide hall full
of small conveyor belts and pulleys; a large pipe runs down the middle. A
plaque on the wall says, "Mechanochemical processing concept, circa 1990." As
usual, all the motions seem rather slow, but in this hall everything that
seems designed to move is visibly in motion. The general flow seems to be away
from the pipe, through several steps, and then up through the ceiling toward
the hall of assemblers above.
After walking over to the pipe, you can see that it is nearly transparent.
Inside is a seething chaos of small molecules: the wall of the pipe is the
boundary between loose molecules and controlled ones, but the loose molecules
are well confined. In this simulation, your fingertips are like small
molecules. No matter how hard you push, there's no way to drive your finger
through the wall of the pipe. Every few paces along the pipe a fitting juts
out, a housing with a mechanically driven rotating thing, exposed to the
liquid inside the pipe, but also exposed to a belt running over one of the
pulleys, embedded in the housing. It's hard to see exactly what is happening.
The tourguide speaks up, saying, "Pockets on the rotor capture single
molecules from the liquid in the pipe. Each rotor pocket has a size and shape
that fits just one of the several different kinds of molecule in the liquid,
so the process is rather selective. Captured molecules are then pushed into
the pockets on the belt that's wrapped over the pulley there, then—"
"Enough," you say. Fine, it singles out molecules and sticks them into this
maze of machinery. Presumably, the machines can sort the molecules to make
sure the right kinds go to the right places.
The belts loop back and forth carrying big, knobby masses of molecules. Many
of the pulleys—rollers?—press two belts together inside a housing with
auxiliary rollers. While you are looking at one of these, the tourguide says,
"Each knob on a belt is a mechanochemical-processing device. When two knobs on
different belts are pressed together in the right way, they are designed to
transfer molecular fragments from one to another by means of a mechanically
forced chemical reaction. In this way, small molecules are broken down,
recombined, and finally joined to molecular tools of the sort used in the
assemblers in the hall above. In this device here, the rollers create a
pressure equal to the pressure found halfway to the center of the Earth,
speeding a reaction that –"
"Fine, fine," you say. Chemists in the old days managed to make amazingly
complex molecules just by mixing different chemicals together in solution in
the right order under the right conditions. Here, molecules can certainly be
brought together in the right order, and the conditions are much better
controlled. It stands to reason that this carefully designed maze of pulleys
and belts can do a better job of molecule processing than a test tube full of
disorganized liquid ever could. From a liquid, through a sorter, into a mill,
and out as tools: this seems to be the story of molecule processing. All the
belts are loops, so the machinery just goes around and around, carrying and
transforming molecular parts.
Beyond Antiques
This system of belts seems terribly simple and
efficient, compared to the ponderous arms driven by frantic computers in the
hall above. Why stop with making simple tools? You must have muttered this,
because the tourguide speaks up again and says, "The Special-Assembler Exhibit
shows another early molecular-manufacturing concept that uses the principles
of this molecule-processing system to build large, complex objects. If a
system is building only a single product, there is no need to have computers
and flexible arms move parts around. It is far more efficient to build a
machine in which everything just moves on belts at a constant speed, adding
small parts to larger ones and then bringing the larger ones together as you
saw at the end of the hall above."
This does seem like a more sensible way to churn out a lot of identical
products, but it sounds like just more of the same. Gears like fused marbles,
belts like coarse beadwork, drive shafts, pulleys, machines and more machines.
In a few places, marbles snap into new patterns to prepare a tool or make a
product. Roll, roll, chug, chug, pop, snap, then roll and chug some more.
As you leave the simulation hall, you ask, "Is there anything important I've
missed in this molecular manufacturing tour?"
The tourguide launches into a list: "Yes—the inner workings of assembler arms,
with drive shafts, worm gears, and harmonic drives; the use of Diels-Alder
reactions, interfacial free-radial chain reactions, and dative-bond formation
to join blocks together in the larger-scale stages of assembly; different
kinds of mechanochemical processing for preparing reactive molecular tools;
the use of staged-cascade methods in providing feed-molecules of the right
kinds with near-perfect reliability; the differences between efficient and
inefficient steps in molecular processing; the use of redundancy to ensure
reliability in large systems despite sporadic damage; modern methods of
building large objects from smaller blocks; modern electronic nanocomputers;
modern methods for—"
"Enough!" you say, and the tourguide falls silent as you pitch it into a
recycling bin. A course in molecular manufacturing isn't what you're looking
for right now; the general idea seems clear enough. It's time to take another
look at the world on a more normal scale. Houses, roads, buildings, even the
landscape looked different out there beyond the Faire dome—less crowded,
paved, and plowed than you remember. But why? The history books (well, they're
more than just books) say that molecular manufacturing made a big
difference; perhaps now the changes will make more sense. Yes, it's time to
leave.
As you toss your goggled, gloved jumpsuit into another bin, a striking
dark-haired woman is taking a fresh one from a rack. She wears a jacket
emblazoned with the name "Desert Rose NanoManufacturing."
"How'd you like it?" she asks with a smile.
"Pretty amazing," you say.
"Yes," she agrees. "I saw this sim back when I was taking my first
molecular-manufacturing class. I swore I'd never design anything so clunky! This
whole setup really brings back the memories—I can't wait to see if it's as crude
as I remember." She steps into the simulation hall and closes the door.
© 1991 by K.
Eric Drexler, Chris Peterson, and Gayle Pergamit. All rights reserved.
If you enjoyed this
excerpt, read the complete book online
here.
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