Biomedical Engineering Reference
In-Depth Information
21.2 NANOMATERIALS
Nanomaterials have been categorized as those materials which have structured components with at
least one dimension less than 100 nm. Materials that have one dimension in the nanoscale (and are
extended in the other two dimensions) are layers, such as thin films or surface coatings. Some of the
features on computer chips come under this category. Materials that are nanoscale in two dimensions
(and extended in one dimension) include nanowires and nanotubes. Materials that are nanoscale in
three dimensions are particles, e.g., precipitates, colloids, and quantum dots (tiny particles of semi-
conductor materials). Nanocrystalline materials, made up of nanometer-sized grains, also fall into this
category. The nanomaterial field includes subfields which study or develop materials having unique
properties arising from their nanoscale dimensions [2] :
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Interface and colloid science has given rise to many materials which may be useful in nanotech-
nology such as carbon nanotubes and other fullerenes and various nanoparticles and nanorods.
Nanomaterials with fast ion transport are also related to nanoionics and nanoelectronics.
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Progress has been made in using these materials for medical applications.
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Nanoscale materials are sometimes used in solar cells which combat the cost of traditional silicon
solar cells.
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Development of applications incorporating semiconductor nanoparticles to be used in the next
generation of products, such as display technology, lighting, solar cells, and biological imaging.
21.2.1 Applications of Nanomaterials
Most current applications represent evolutionary developments of existing technologies: e.g., the
reduction in size of electronics devices.
21.2.1.1 Sunscreens and Cosmetics
Nanosized titanium dioxide and zinc oxide are currently used in some sunscreens, as they absorb and
reflect ultraviolet (UV) rays and yet are transparent to visible light and so are more appealing to the
consumer.
21.2.1.2 Composites
Nanoparticles and nanotubes are used in composites, materials that combine one or more separate
components and which are designed to exhibit better overall properties than each of components.
21.2.1.3 Clays
Clays containing naturally occurring nanoparticles have long been important as construction materi-
als and are undergoing continuous improvement. Clay-particle-based composites—containing plas-
tics and nanosized flakes of clay—are also finding applications such as use in car bumpers.
21.2.1.4 Coatings and Surfaces
Coatings with thickness controlled at the nano- or atomic scale have been in routine production for
some time. Recent applications include the self-cleaning window, which is coated in highly activated
titanium dioxide, engineered to be highly hydrophobic (water repellent) and antibacterial, and coat-
ings based on nanoparticulate oxides that catalytically destroy chemical agents.
 
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