Nanotechnology, also shortened to nanotech, is
the use of matter on an atomic, molecular, and
supramolecular scale for industrial purposes. The
earliest, widespread description of nanotechnology
referred to the particular technological goal of
precisely manipulating atoms and molecules for
fabrication of macroscale products, also now referred
to as molecular nanotechnology.
 A more
generalized description of nanotechnology was
subsequently established by the National
Nanotechnology Initiative, which defined
nanotechnology as the manipulation of matter with at
least one dimension sized from 1 to 100 nanometers.
This definition reflects the fact that quantum mechanical effects are important at this quantum-realm
scale, and so the definition shifted from a particular technological goal to a research category
inclusive of all types of research and technologies that deal with the special properties of matter
which occur below the given size threshold. It is therefore common to see the plural form
“nanotechnologies” as well as “nanoscale technologies” to refer to the broad range of research and
applications whose common trait is size.
Nanotechnology as defined by size is naturally broad, including fields of science as diverse as surface
science, organic chemistry, molecular biology, semiconductor physics, energy storage,
 and molecular engineering.
 The associated research and
applications are equally diverse, ranging from extensions of conventional device physics to
completely new approaches based upon molecular self-assembly,
from developing new materials
with dimensions on the nanoscale to direct control of matter on the atomic scale.
Scientists currently debate the future implications of nanotechnology. Nanotechnology may be able to
create many new materials and devices with a vast range of applications, such as in nanomedicine,
nanoelectronics, biomaterials energy production, and consumer products. On the other hand,
nanotechnology raises many of the same issues as any new technology, including concerns about the
toxicity and environmental impact of nanomaterials, and their potential effects on global
economics, as well as speculation about various doomsday scenarios. These concerns have led to a
debate among advocacy groups and governments on whether special regulation of nanotechnology is
Nanotechnology is the engineering of functional systems at the molecular scale. This covers both
current work and concepts that are more advanced. In its original sense, nanotechnology refers to the
projected ability to construct items from the bottom up, using techniques and tools being developed
today to make complete, high-performance products.
One nanometer (nm) is one billionth, or 10−9
, of a meter. By comparison, typical carbon-carbon bond
lengths, or the spacing between these atoms in a molecule, are in the range 0.12–0.15 nm, and a DNA
double-helix has a diameter around 2 nm. On the other hand, the smallest cellular life-forms, the
bacteria of the genus Mycoplasma, are around 200 nm in length. By convention, nanotechnology is
taken as the scale range 1 to 100 nm following the definition used by the National Nanotechnology
Initiative in the US. The lower limit is set by the size of atoms (hydrogen has the smallest atoms,
which are approximately a quarter of a nm kinetic diameter) since nanotechnology must build its
devices from atoms and molecules. The upper limit is more or less arbitrary but is around the size
below which the phenomena not observed in larger structures start to become apparent and can be
made use of in the nano device. These new phenomena make nanotechnology distinct from
devices which are merely miniaturised versions of an equivalent macroscopic device; such devices are
on a larger scale and come under the description of microtechnology.
To put that scale in another context, the comparative size of a nanometer to a meter is the same as
that of a marble to the size of the earth. Or another way of putting it: a nanometer is the amount
an average man’s beard grows in the time it takes him to raise the razor to his face.
Two main approaches are used in nanotechnology. In the “bottom-up” approach, materials and
devices are built from molecular components which assemble themselves chemically by principles of
 In the “top-down” approach, nano-objects are constructed from larger
entities without atomic-level control.
Areas of physics such as nanoelectronics, nanomechanics, nanophotonics and nanoionics have
evolved during the last few decades to provide a basic scientific foundation of nanotechnology.
Several phenomena become pronounced as the size of the system decreases. These include statistical
mechanical effects, as well as quantum mechanical effects, for example the “quantum size effect”
where the electronic properties of solids are altered with great reductions in particle size. This effect
does not come into play by going from macro to micro dimensions. However, quantum effects can
become significant when the nanometer size range is reached, typically at distances of 100
nanometers or less, the so-called quantum realm. Additionally, a number of physical (mechanical,
electrical, optical, etc.) properties change when compared to macroscopic systems. One example is
the increase in surface area to volume ratio altering mechanical, thermal and catalytic properties of
materials. Diffusion and reactions at nanoscale, nanostructures materials and nanodevices with fast
ion transport are generally referred to nanoionics. Mechanical properties of nanosystems are of
interest in the nanomechanics research. The catalytic activity of nanomaterials also opens potential
risks in their interaction with biomaterials.