Biomedical Engineering Reference
In-Depth Information
exhibit properties distinctively dif erent from their bulk and molecular
counterparts. h e properties of these materials are characterized by their
nanometer dimensions. h ey are considered to be the building blocks for
nanotechnology and are referred to particles with at least dimension of
100 nm. A nanometer is approximately 100,000 times smaller than the
diameter of a human hair. Some nanomaterials occur naturally but some
of these materials are designed and already being used in many commer-
cial products such as sunscreens, cosmetics, sporting goods, stain-resistant
clothing, tires, electronics as well as many other everyday items and are
used in medicine for purposes of diagnosis, imaging and drug delivery [5].
If the physical size of the material is reduced below this nanometer
scale, its properties change and become sensitive to its size and shape [6].
Surfaces and interfaces are important in explaining nanomaterials behav-
ior [7]. h e reason for variation of properties with size of the materials is
due to extremely high surface to volume ratio. In bulk materials, only a
relatively small percentage of atoms will be at or near a surface or inter-
face but in nanomaterials, the small feature size ensures that many atoms
will be near interfaces. Number of surface atoms increases with decreas-
ing particle size. For example, in a cube of edge size 1 cm, the percentage
of surface atoms would be 10
-5
% of the bulk atoms, for a cube of edge
size 10 nm, percentage of surface atoms would be 10 % of the bulk atoms
whereas for a cube of edge 1 nm every atom can be a surface atom.
Surface properties such as energy levels, electronic structure and reactiv-
ity can be quite dif erent from interior states and give rise to dif erent mate-
rial properties. Reducing the size of nanoparticles has a profound ef ect on
the energy level spacing as the system becomes more coni ned. Particles in
these size ranges have been used by several industries and humankind for
thousands of years; however, there has been a recent resurgence because of
the ability to synthesize and manipulate such materials.
Nanomaterials i nd use in a variety of dif erent areas, such as electronic,
magnetic and optoelectronic, biomedical, pharmaceutical, cosmetic,
energy, environmental, catalytic and materials applications. h ere are novel
UV-blocking coatings on glass bottles which protect beverages from dam-
age by sunlight and longer-lasting tennis balls using butyl rubber/nano-
clay composites. Many i nds application in cosmetics, sun-block creams,
self-cleaning windows and nanoscale silica is being used as i ller in a range
of products, including cosmetics and dental i llings. Major emphasis is also
being put on ensuring broader social improvements and sustainable devel-
opment [8]. Nanomaterials are not simply another step in miniaturization,
but a dif erent area entirely. h e nanoworld lies midway between the scale
of atomic and quantum phenomena, and the scale of bulk materials.
