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Nanoscale Science
“Marvels of an invisible world” was how a recent article on nanotechnology in the
German Manager Magazin depicted one of the great hopes in the area of novel technological
developments. But what’s behind it? What is nanotechnology and what are nanoscale sciences? And why is
this seen as one of the key technologies for the future?
It’s the little things that count in research
Nanoscale science and nanotechnology deal literally with the small things in life. One million of the
objects studied would fit onto the dot on this “i”. Unimaginable? Invisible? Impossible to comprehend? Not
at all. Objects of such tiny proportions can be observed, measured, analyzed and modified. Around the
world, nanoscientists are using ever more sensitive instruments. And they are now able to detect and
manipulate atoms which have a diameter of about 0.3nm.
Breakthrough with new materials and microscopes
The rapid advances being made today in nanoscale science were only made possible by new materials
(e.g. carbon nanotubes) and the development of a
special microscope, for which its inventors were awarded the Nobel prize. In 1981, a group of IBM scientists
led by Gerd Binning, Heinrich Rohrer and Christoph Gerber invented the scanning tunneling microscope, which
enabled the individual atoms of a surface to be visualized for the first time. This microscope is based on
principles quite different from those of the light or electron microscopes that were known hitherto. In the
scanning tunneling microscope, the surface of a sample is scanned in minute detail by a fine measuring probe
to produce an accurate image of this surface. The laws of physics ensure that a far higher resolution is
achieved than was possible using a light or electron microscope. The invention of the scanning tunneling
microscope was followed by further developments based on a similar principle (e.g. AFM, atomic force microscope),
all of which are described as scanning probe microscopes.
Wide range of applications
In addition to their high resolution, scanning probe microscopes also offer the crucial advantage that
they do not require any major sample preparation, so that biomolecules can be analyzed in their natural
environment. And in the process they not only provide exact images of surfaces, with their aid various
physical and chemical properties can also be measured. In addition, scanning probe microscopes can also be
used as tools and selectively modify samples. The tip of an atomic force microscope, for example, can be made
to vibrate like a miniature pneumatic hammer and etch information into a surface. Scanning tunneling
microscopes can also be used for writing by “packing” and shifting individual atoms.
The beginning of the nano age
As our understanding of the laws and principles of the nano world grows, so nanoscale science will be
applied to nanotechnology, which will bring about changes in many aspects of our lives. And we are
already starting to benefit from its achievements. Sun protection factors in suncreams and special color
effects in car paints are based on nano particles; antireflection coatings on glasses and contact lenses
are being optimized thanks to nanotechnology; blood filters of dialysis patients can today be reused for
the benefit of patients with the added bonus of reducing costs, on the basis of nanotechnological
studies, and new nanotechnology-based dosage forms for medicines are also coming onto the market. In the
future, nanotechnology will have a major influence on many different areas of information and communications
technology and life sciences, as well as on the sustainable use of resources. New nanomaterials and storage
media, atomic switches, nano robots for the human body, artificial mechanical noses and ears – these are
examples of developments which scientists around the world are already working on. Further innovations will
come in the next few years and show why nanotechnology is being described today as a key technology of the
future. As Nobel prize laureate Gerd Binning observed “the nano age has only just begun”.
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What does nano mean?
The term “nano” comes from the Greek “nanos” meaning “dwarf”. Now, nanoscientists do not
deal with dwarfs, elves or trolls, but with objects which measure just a few nanometers across. In
this context, “nano” denotes one thousand millionth or one billionth. As a unit of length,
therefore, 1 nanometer is billionth of a meter (0.000'000'001m) or one millionth of a
millimeter. By the same token, for example, a nanogram is one billionth of a gram, and a nanosecond
is one billionth of a second.
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Nanometer world
The world of structures that measure just a few nanometers, or millionths of a millimeter, are not
detectable either by the human eye or by light microscopes. Yet these are the dimensions
of the building blocks of matter – atoms and molecules. Their visualization and analysis offer
scientists important new insights, because the function of an object is often determined in the fine
detail of its structure. At the level of atoms and molecules, we see a blurring of boundaries between
the classical disciplines such as physics, biology and chemistry. So only through the work of
interdisciplinary teams can the laws governing the nanoworld be researched.
The dimensions in which nanoresearch operates are illustrated by the following example:
If an atom were inflated to the size of an apple, the size of the apple itself would increase to that
of the planet, assuming the same degree of magnification.
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Scanning probe microscopes
The most important scanning probe microscopes are scanning tunneling and atomic force microscopes.
Scanning tunneling microscope (STM)
If metals or semiconductors are to be studied, the conductive properties can be exploited for imaging
purposes. If a voltage is applied between two electrical conductors, then an electrical current flows
between the two. This current does not only flow when the two bodies touch but also when they are very
close to each other. The intensity of this “tunneling current” is strongly dependent on the distance
between the two bodies. An increase in the distance by the diameter of one atom (0.3 nm) is enough to
produce a 1000-fold reduction in the tunneling current.
A fine tip of conductive material now scans the likewise conductive sample in the scanning tunneling
microscope. The tunneling current is measured and allows conclusions to be drawn on the distance
between the probe and the sample and thus on the nature of the surface.
Atomic force microscope (AFM)
In the scanning or atomic force microscope (AFM), non-conductive materials can also be studied. In
this case, the probe is attached to a fine cantilever. As the sample is scanned, the deflection of the
cantilever is measured. This may occur, for example, by means of a laser beam which is focused on the
cantilever and its deflection then measured. Computers are then used to “translate” these data into
images in which the surface of the sample is reconstructed.
Do you want to know more about AFM and STM? Then please read:
Nanometer Scale Science and Technology - The Impact of STM and AFM
by M. Hegner and H.-J. Güntherodt, 2001
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