Biomedical Engineering Reference
In-Depth Information
This supercritical state is very sensitive to the process' parameters and tunable.
Methods using fl uids in such a unique state are now used for the synthesis of nano-
particles, exploiting the rapid expansion of the supercritical solution, and they are
also used for coating and fi lling nanostructures (Ye et al.
2004
) . The most common
reaction media used in this process are supercritical carbon dioxide (scCO
2
) and
water (scH
2
O) because they are nontoxic, nonfl ammable, inexpensive, and environ-
mentally benign. In addition, they ensure much higher reaction rates and an increased
selectivity. Although it has many advantages, supercritical fl uid synthesis remains
technically demanding, and it is still being adapted for large-scale production.
2
Conclusions
Top-down and bottom-up approaches are complementary in nanofabrication and
comprise a numerous set of techniques. Their use and development have been at the
center of material research for the past few decades, promising a wide range of
applications in (non)biologically related nanotechnology fi elds. The use of a par-
ticular approach is often dictated by the specifi c need for a particular characteristic,
shape, or composition of the nanomaterials for the different applications. Often,
methods are used in combination to complement each other.
This chapter presented a brief overview of the most common techniques used for the
fabrication of nanostructured bulk materials and nanomaterials with potential applica-
tions in biology and bioengineering fi elds. Most of the techniques described are continu-
ously evolving even as we write and they represent a wide and active area of research in
physics, chemistry, and engineering fi elds. A deep understanding of the mechanisms
behind all the nanofabrication methods requires a broad and profound knowledge of the
interdisciplinary aspects that regulate the properties of the materials and of the processes
used. The details of the chemistry, physics, and mechanics of these methods go beyond
the scope of this chapter and can be found in the related technical literature.
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