Building Machines from the Atoms Up
Source: The Boston
Globe
July 25, 2000
The pop star physicist, Richard Feynman, had lots of clever ideas
in his lifetime, including a few that won him a Nobel Prize, but what he might
be best remembered for 100 years from now is something he tossed off almost in
passing back in 1959.
All artifacts of human technology, from Stone Age choppers to
automobiles, have been fashioned by taking a lump of preexisting amorphous
matter and chipping, carving, bending, or bashing it into shape.
But there's another way, suggested Feynman, and that's starting
from the bottom and assembling artifacts atom by atom. Back in 1959, it was hard
to imagine how this might be done, but there is no physical law that would
prevent it, he said.
Nowadays, Feynman's idea is all the rage. It's called
nanotechnology (from the nanometer, a unit of measurement a billionth of a meter
long). A recent story in US News & World Report hailed nanotechnology as the
''next industrial revolution.''
The magazine quotes Mihail Roco, a senior adviser for
nanotechnology at the National Science Foundation: ''Because of nanotech, we
will see more change in our civilization in the next 30 years than we did during
all of the 20th century.''
That's quite a claim, and we'll have to wait and see if it
happens. Granted, computer circuits continue to shrink, and gears and motors
have been devised that could fit on the head of a pin, but these have mostly
been created in the old-fashioned way, by etching a block of amorphous matter -
usually silicon.
Which is not to say that atom-by-atom fabrication is all talk.
Single atoms can be arranged on a flat surface with a device called a scanning
tunneling microscope. And three-dimensional structures, such as computer
circuits, can be built up by depositing successive layers of molecules that are
only a single molecule thick.
So how long until we see the famously predicted ''utility fog,'' a
mist of microscopically-small mechanical robots (nanobots), fabricated atom by
atom, that can assemble themselves in their teeming numbers into anything from a
comfy chair to a computer? How long until we inject nanobots into the
bloodstream by hypodermic to seek out cancer cells and disassemble them atom by
atom? How long until we send invisible clouds of nanobots into an enemy's
territory to disassemble everything and everybody into a ''gray goo?'' Longer, I
suspect, than the cheerleaders (or doom-mongers) of nanotech would have us
believe.
But, of course, Feynman was right: There is no law of physics to
keep it from happening. We know that incredibly sophisticated machines can be
fabricated molecule-by-molecule on a microscopic scale. Nature does it every
day.
As I write, a vast army of red spider mites is encamped outside my
window - on the sill and window panes. They are taking advantage of the dry,
bright weather to feast on the plants in the window box. At first glance, they
appear to be specks of red ink, about the size of the period at the end of this
sentence; but then you notice that the specks are moving. Under a magnifier they
become gorgeous scarlet animals, with six articulated legs and waving antennae.
Where did these little fellows come from? Certainly, nature didn't
carve them from an amorphous block of matter, the way we make arrowheads and
computer chips. Nature assembled them atom by atom - eyes, mouth, belly, anus,
genitals, heart, brain, nervous system - something like 10 quadrillion atoms in
all, every one in its proper place.
Red spider mites are visible to the unaided eye, if only barely.
The dust mites in my bed are too small to see without a microscope, but they are
there by the tens of thousands (don't smirk, they are in your bed, too).
Electron microscope photographs of dust mites show every bristle and hair. Quel
monstre! These all-natural nanocreatures go about their business, eating the
skin flakes that fall from our bodies, and there is almost nothing we can do
about them.
Will nanoengineers create mite-sized R2D2s - microscopic
mechanical robots that will go into our beds and do battle with dust mites? And
then, having cleared our beds of dust mites, and skin flakes, too, march out
onto the window sill to gang up on the spider mites and save the plants? That's
what the nanogurus are telling us.
Don't hold your breath. Maybe in 100 years, but not 30.
Meanwhile, we will certainly see nanocreatures doing useful things
by human design (we have them already). They won't be microscopic mechanical
robots assembled atom by atom with technologies like the scanning tunneling
microscope. Rather, they will be ordinary organisms, bacteria most likely, but
maybe dust mites, too, that have been genetically engineered to make them do
things we want them to do - like eat bad germs, clean up oil spills, or take up
residence in someone else's bed.
What nature does, we also can do - by borrowing nature's DNA
technology.
Chet Raymo is a professor of physics at Stonehill College and the
author of several books on science.
by
Chet Raymo
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