Nanotechnology
Last updated: June 21, 2010.
Imagine if you climbed out of the
shower only to discover you'd shrunk in the wash by about 1500 million times! If you
stepped into your living room, what you'd see around you would not be
chairs, tables, computers, and
your family but atoms, molecules, proteins, and cells. Shrunk down to the
"nanoscale," you'd not only see the atoms that everything is made
from—you'd actually be able to move them around! Now suppose you
started sticking those atoms together in interesting new ways, like
tiny Lego® bricks of nature. You could build all kinds of
fantastic materials, everything from brand new medicines to
ultra-fast computer chips. Making new things on this incredibly small
scale is called nanotechnology and it's one of the most exciting and
fast-moving areas of science and technology today.
Photo: Looking into the nanoworld: Sulfur atoms arranged on a layer of copper deposited onto a crystal of ruthenium. By courtesy of US Department of Energy/Brookhaven National Laboratory.
From nanoscience to nanotechnology
This is all very interesting and quite impressive,
but what use is it? Our lives have some meaning on a scale of meters,
but it's impossible to think about ordinary, everyday existence on a
scale 1000 times smaller than a fly's eye. We can't really think
about problems like AIDS, world poverty, or global warming, because
they lose all meaning on the nanoscale. Yet the nanoscale—the world
where atoms, molecules (atoms joined together), proteins, and cells rule the roost—is a
place where science and technology gain an entirely new meaning.
By zooming in to the nanoscale, we can figure out
how some of the puzzling things in our world actually work by seeing
how atoms and molecules make them happen. You've probably seen that
trick TV programs do with satellite photos, where they start off with
a picture of the green and blue Earth and zoom in really fast, at
ever-increasing scale, until you're suddenly staring at someone's
back garden. You realize Earth is green because it's made from a
patchwork of green grass. Keep zooming in and you'll see the
chloroplasts in the grass: the green capsules inside the plant cells
that make energy from sunlight. Zoom in some more and you'll
eventually see molecules made from carbon, hydrogen, and oxygen being
split apart
and recombined inside the chloroplasts. So the nanoscale is good
because it lets us do nanoscience: it helps
us understand why
things happen by studying them at the smallest possible scale. Once
we understand nanoscience, we can do some nanotechnology: we can put
the science into action to help solve our problems. That's what the
word "technology" means and it's how technology (applied science)
differs from pure science, which is about studying things for their
own sake.
What's so good about the nanoscale?
It turns out there are some very interesting
things about the nanoscale. Lots of substances behave very
differently in the world of atoms and molecules. For example, the
metal copper is transparent on the nanoscale while
gold, which is
normally unreactive, becomes chemically very active. Carbon, which is
quite soft in its normally occurring form (graphite), becomes
incredibly hard when it's tightly packed into a nanoscopic
arrangement called a nanotube. In other
words, materials can
have different physical properties on the
nanoscale even
though they're still the same materials! On the nanoscale, it's
easier for atoms and molecules to move around and between one
another, so the chemical properties of
materials can also be
different. Nanoparticles have much more surface area exposed to other
nanoparticles, so they are very good as catalysts (substances that
speed up chemical reactions).
Photo: Looking at the nanoscale with electron
holography.
By courtesy of US Department of Energy/Brookhaven National Laboratory.
One reason for these differences is that different
factors become important on the nanoscale. In our everyday world,
gravity is the most important force we encounter: it dominates
everything around us, from the way our hair hangs down around our
head to the way Earth has different seasons at different times of
year. But on the nanoscale, gravity is much less important than the
electromagnetic forces between atoms and molecules. Factors like
thermal vibrations (the way atoms and molecules store heat by
jiggling about) also become extremely significant. In short, the game
of science has different rules when you play it on the nanoscale.
How do you work on the nanoscale?
Your fingers are millions of nanometers long, so
it's no good trying to pick up atoms and molecules and move them
around with your bare hands. That would be like trying to eat your
dinner with a fork 300 km (186 miles) long! Amazingly, scientists
have developed electron microscopes
that allow us to "see" things on the
nanoscale and also manipulate them. They're called atomic force
microscopes (AFMs), scanning probe microscopes (SPMs), and scanning
tunneling microscopes (STMs).
Photo: The eight tiny probe tips on the
Atomic Force Microscope (AFM) built into NASA's Phoenix Mars Lander.
The tip enlarged in the circle is the same size as a smoke particle at its base (2 microns).
Photo by courtesy of NASA Jet Propulsion Laboratory (NASA-JPL).
The basic idea of an electron microscope is to use
a beam of electrons to see things that are too small to see using a
beam of light. A nanoscopic microscope uses electronic and quantum
effects to see things that are even smaller. It also has a tiny probe
on it that can be used to shift atoms and molecules around and
rearrange them like tiny building blocks. In 1989, IBM researcher Don
Eigler used a microscope like this to spell out the word I-B-M by
moving individual atoms into position. Other scientists have used
similar techniques to draw pictures of nanoscopic guitars, books, and
all kinds of other things. These are mostly frivolous exercises,
designed to wow people with nanopower. But they also have important
practical applications. There are lots of other ways of
working with nanotechnology, including molecular beam epitaxy,
which is a way of growing single crystals one layer of atoms at a time.
What can we use nanotechnology for?
Most of nanotechnology's benefits will happen
decades in the future, but it's already helping to improve our world
in many different ways. We tend to think of nanotechnology as
something new and alien, perhaps because the word "technology"
implies artificial and human-made, but life itself is an example of
nanotechnology: proteins, bacteria, viruses, and cells all work on
the nanoscopic scale.
Nanomaterials
It could be you're already using nanotechnology.
You might be wearing nanotechnology pants (that's "trousers" to
you in the UK), walking on a nanotechnology rug, sleeping on
nanotechnology sheets, or hauling nanotechnology luggage to the
airport. All these products are made from fabrics coated with
"nanowhiskers." These tiny surface fibers are so small that dirt
cannot penetrate into them, which means the deeper layers of material
stay clean. Some brands of sunscreens use
nanotechnology in a similar
way: they coat your skin with a layer of nanoscopic titanium dioxide
or zinc oxide that blocks out the Sun's harmful ultraviolet rays.
Nano-coatings are also appearing on scratch-resistant car bumpers,
anti-slip steps on vans and buses, corrosion resistant paints, and
wound dressings.
Carbon nanotubes are among the most exciting of
nanomaterials. These rod-shaped carbon molecules are roughly one
nanometer across. Although they're hollow, their densely packed
structure makes them incredibly strong and they can be grown into
fibers of virtually any length. NASA scientists have recently
proposed carbon nanotubes could be used to make a gigantic elevator
stretching all the way from Earth into space. Equipment and people
could be shuttled slowly up and down this "carbon ladder to the
stars," saving the need for expensive rocket flights.
Photo: Making an electric circuit with carbon
nanotubes.
A carbon nanotube (shown here in light blue at the top) is connected to
an electricity supply
using aluminum (shown in dark blue at the bottom).
Picture by courtesy of NASA Marshall Space Flight Center (NASA-MSFC).
Nanochips
One form of nanotechnology we all use is
microelectronics. The "micro" part of that word suggests computer
chips work on the microscopic scale—and they do. But since terms
like "microchip" were coined in the 1970s, electronic engineers
have found ways of packing even more transistor
switches into
circuits to make computers that are smaller, faster, and cheaper than
ever before. This constant increase in computing power goes by the
name of Moore's Law, and nanotechnology will
ensure it
continues well into the future. Everyday transistors in the early
21st-century are just 100-200 nanometers wide, but
cutting-edge experiments are already developing much smaller devices.
In 1998, scientists made a transistor from a single carbon nanotube.
Photo: Creatures of the nanoworld? This is what a
single molecule of the semiconductor material cadmium sulfide looks
like.
Nanoparticles like this could be used to make improved electronic
displays and lasers.
Picture by courtesy of NASA Marshall Space Flight Center (NASA-MSFC).
And it's not just the chips inside computers
that use nanotechnology. The displays on everything from iPods
and cellphones to laptops and flatscreen TVs are
shifting to
organic light-emitting diodes (OLEDs), made from plastic
films built on the nanoscale.
Nanomachines
One of the most exciting areas of nanotechnology
is the possibility of building incredibly small machines—things
like gears, switches,
pumps, or
engines—from individual atoms.
Nanomachines could be made into nanorobots (sometimes called
"nanobots") that could be injected into our bodies to carry out
repairs or sent into hazardous or dangerous environments, perhaps to
clean up disused nuclear power plants.
As is so often the case,
nature leads humans here. Scientists have already found numerous
examples of nanomachines in the natural world. For example, a common
bacteria called E.coli can build itself a
little
nanotechnology tail that it whips around like a kind of propeller to
move it closer to food. Making nanomachines is also known as
molecular manufacturing and
molecular nanotechnology (MNT).
Photo: The world's smallest chain drive.
An example of a nanomachine, this nanotechnology "bike chain" and gear
system was developed by scientists
at Sandia National Laboratory.
By courtesy of US Department of Energy/Sandia National Laboratory.
History of nanotechnology
Natural examples like this tell us that
nanotechnology is as old as life itself, but the concept of the
nanoscale, nanoscience we can study, and nanotechnology we can
harness are all relatively new developments. The brilliant American
physicist Richard Feynman (1918–1988) is widely credited with
kick-starting modern interest in nanotechnology. In 1959, in a famous
after-dinner speech called "There's plenty of room at the
bottom," the ever-imaginative Feynman speculated about an
incredibly tiny world where people could use tiny tools to rearrange
atoms and molecules. By 1974, Japanese engineering professor Norio
Taniguchi had named this field "nanotechnology."
Nanotechnology really took off in the 1980s. That
was when nanotech-evangelist Dr K. Eric Drexler first published his
groundbreaking book Engines of Creation: The
Coming Era of Nanotechnology. It was also the decade when microscopes appeared
that were capable of manipulating atoms and molecules on the
nanoscale. In 1991, carbon nanotubes were discovered by another
Japanese scientist, Sumio Iijima, opening up huge interest in new
engineering applications. The graphite in pencils is a soft form of
carbon. In 1998, some American scientists built themselves another
kind of pencil from a carbon nanotube and then used it, under a
microscope, to write the words "NANOTUBE NANOPENCIL" with letters
only 10 nanometers across.
Stunts like this captured the public imagination,
but they also led to nanotechnology being recognized and taken
seriously at the highest political levels. In 2000, President Bill
Clinton sealed the importance of nanotechnology when he launched a
major US government program called the National Nanotechnology
Initiative (NNI), designed to fund groundbreaking
research and inspire public interest.
The future of nanotechnology: nanodream or nano-nightmare?
Engineers the world over are raving about
nanotechnology. This is what scientists at one of America's premier
research institutions, the Los Alamos National Laboratory, have to
say: "The new concepts of nanotechnology are so
broad and
pervasive, that they will influence every area of technology and
science, in ways that are surely unpredictable.... The total societal
impact of nanotechnology is expected to be greater than the combined
influences that the silicon integrated circuit, medical imaging,
computer-aided engineering, and man-made polymers have had in this
century." That's a pretty amazing claim: 21st-century
nanotechnology will be more important than all the greatest
technologies of the 20th century put together!
Photo: These nanogears were made by attaching
benzene molecules (outer white blobs) to the outsides of carbon
nanotubes (inner gray rings).
By courtesy of Great Images in NASA.
Nanotechnology sounds like a world of great
promise, but there are controversial issues too that must be
considered and resolved. Some people have raised concerns that
nanoscale organisms or machines could harm human life or the
environment. One problem is that tiny particles can be extremely
toxic to the human body. No-one really knows what harmful effect new
nanomaterials or substances could have. Chemical pesticides were not
considered harmful when they were first used in the early decades of
the 20th century; it wasn't until the 1960s and 1970s
that their potentially harmful effects were properly understood.
Could the same happen with nanotechnology?
The ultimate nano-nightmare, the problem of "gray
goo," was first highlighted by Eric Drexler. What happens if
well-meaning humans create nanobots that run riot through the
biosphere, gobbling up all living things and leaving behind nothing
but a chewed-up mass of "gray goo"? Critics of nanotechnology
argue humans shouldn't meddle with worlds they don't understand,
but if we took that argument to its logical conclusion, we'd have
no inventions at all—no medicines, no transportation, no
agriculture, and no education—and we'd still be living in the
Stone Age. The real question is whether the promise of nanotechnology
is greater than any potential risks that go with it. And that will
determine whether our nano-future becomes dream—or
nightmare.
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