Biomedical Engineering Reference
In-Depth Information
In a recent extensive discussion about a framework for
definitions presented to the European Commission, the nano-scale
has been defined as being of the order of 100 nm or less. Similarly,
a nanomaterial has been defined as “any form of a material that
is composed of discrete functional parts, many of which have one
or more dimensions of the order of 100 nm or less” [91]. Other
definitions logically follow this approach such as: a nanocrystalline
material is “a material that is comprised of many crystals, the
majority of which have one or more dimensions of the order of
100 nm or less” (normally, with presence of neither the micron-
sized crystals nor an intergranular amorphous phase) and a
nanocomposite is a “multi-phase material in which the majority of
the dispersed phase components have one or more dimensions of
the order of 100 nm or less” [89]. Similarly, nanostructured materials
are defined as the materials containing structural elements (e.g.,
clusters, crystallites or molecules) with dimensions in the 1-100 nm
range [92], nanocoatings represent individual layers or multilayer
surface coatings of 1-100 nm thick, nanopowders are extremely fine
powders with an average particle size in the range of 1-100 nm and
nanofibers are the fibers with a diameter within 1-100 nm [93, 94].
It also has been proposed to extend the lower size limit to 0.1 nm
[95], which would include all existing organic molecules, allowing
chemists to rightly claim they have been working on nanotechnology
for very many years [96].
Strictly speaking, there are serious doubts that the term
“nanomaterial” has a reasonable meaning. For example, let me
cite Prof. David F. Williams, the Editor-in-Chief of
:
“… some words which have no rational basis whatsoever become
part of everyday language so rapidly, even if so illogically, that it is
impossible to reverse the process and their common use has to be
accepted, or perhaps, accommodated. Nanomaterial is one such
word, where I have argued that it should not exist, but accept that
it does through common usage and have to recognize its existence
[89]. The discussion about nanomaterial provides a hint of the
analysis of a biomaterial that follows, since a prefix, which is an
indicator of scale, cannot specify the integer that follows (in this case
a material) unless that integer can be qualified by that scale. In other
words, it is very clear what a nanometer is because nano means
10
Biomaterials
−9
and a meter is a measure of length. In the case of nanomaterial,
what is it about the material that is 10
−9
. Is it the dimension of a
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