Biomedical Engineering Reference
In-Depth Information
General Characteristics of Nanomaterials
Nanomaterials are defined as species with one or more dimensions less than 100 nm [1]. This
size limit has a vital effect on their properties. Consequently, the prefix “nano” applied to the
word “material” does not just imply that the object is “1000 times smaller than micro”
(or its size is nine orders of magnitude less than the basic meter unit), it signifies unique qual-
ities of nanospecies. A nanomaterial notably benefits by shrinking its size towards atomic-
molecular dimensions. As a result, characteristics of such species are entirely different from
those of its bulk counterpart [2-6]. Obviously, there is potential for significant advancement
when advantage is taken of the properties of nanomaterials. Nanotechnology represents
much more than just a reduction of microtechnology dimensions to smaller sized objects; it
creates entirely new phenomena that open various innovative prospects for materials that are
manufactured at the nanoscale. It is quite impressive that the developments achieved in
research laboratories are very quickly taken up by industry and ultimately transferred into
improved goods containing nanocomponents that are ultimately available for consumers.
Size is an obvious important feature associated with nanomaterials, which governs their
unique surface characteristics: their surface-area/volume ratio is huge because a large
fraction of atoms remains on the surface [2, 5, 7]; a combination of surface effects, the
quantum-size effect and macroscopic quantum tunneling effect often results in remarkable
physical and chemical properties of nanomaterials. It is important to mention that
properties of nanomaterials are very different from those associated with their larger coun-
terparts of the same chemical composition. Some unique properties of nanomaterials
include greater hardness, rigidity, higher thermal stability, yield strength, flexibility, and
ductility [5, 8-10]. These characteristics facilitate commercial, technological, and
therapeutic applications of a broad group of artificial nanomaterials. Other unique char-
acteristics of nanomaterials include improved electromagnetic, catalytic, and pharmacoki-
netic properties. These properties are important when nanomaterials are used in medicine
and pharmacy. The associated applications are based on biosensing, magnetic resonance
imaging, optical detection, and the possible role of selected nanostructures in novel
approaches to the drug-delivery processes [11-16].
The list of consumer goods developed and manufactured using nanotechnology is con-
stantly increasing. After more than 20 years of basic and applied research, nano-based prod-
ucts are gaining a vital position in commercial use. According to a current analysis, 1317
different products containing nanomaterials were marketed as of March 2011 [17]. The
consumer goods include sunscreens, toothbrushes, dental bonding, paints, textiles, plastic
wrap, cordless power tools, waterless car wash, corrosion-resistance, guitar strings, golf clubs,
tennis rackets, washing machines, refrigerators, solar batteries, catalyzers, computer chips,
cell phones, and other electronics. According to the Project on Emerging Nanotechnologies
(http://www.nanotechproject.org/inventories/consumer/), three to four new nanotechnology-
based consumer products are introduced weekly onto the market. By 2014, the economic
impact of nanotechnology worldwide is expected to exceed $2.7 trillion [18]. This also corre-
sponds to a large tonnage of nanomaterials to be manufactured by industry, which is esti-
mated at about 58,000 tons in year 2020. Figures 5.1 and 5.2 illustrate the growth of consumer
products during the period 2005-2010, and also the distribution of these products in different
categories [19].
Nanomaterials are not new to our planet: they have been part of the Earth system since
its earliest stages. Natural nanospecies originate from various sources and processes,
including volcanic eruptions, erosion, and combustion, but human activities have added
another component - anthropogenic materials; for example, they are released as soot during
burning, with perhaps automobile exhaust being responsible for a large fraction of such
