Biomedical Engineering Reference
In-Depth Information
Fig. 5
System model for
nanocomposites produced by
sol-gel (modifi ed from
Luther
2004
)
Dissolved
Reaction
Drying
Precursor
Sol
Gel
Aerogel
Thin Film
Coating
Powders
Xerogel
Fig. 6
Basic fl ow of a sol-gel process (modifi ed from Madou
2002
)
very cost-effective and versatile. It has been further developed in last year for the
production of advanced nanomaterials and coatings but also in bio-MEMS appli-
cation for the production of piezoelectrics, such as lead-zirconium-titanate (PZT)
(Madou
2002
) or membranes (Guizard et al.
1992
). Sol-gel processes are well-
adapted for oxide nanoparticles (Lakshmi et al.
1997
) and composite nanopowder
synthesis as well as for access to organic-inorganic materials. A summary of all
the possible interlinked combination of organic and inorganic nanocomposites
that are produced by the sol-gel method is provided in Fig.
5
.
The basic fl ow of the sol-gel process is described in Fig.
6
. The “sol” is prepared
by mechanically mixing a liquid alkoxide precursor (such as tetramethoxysilane,
TMOS, or tetraethoxysilane, TEOS), water, a cosolvent, and an acid or base catalyst
at room temperature. During this step, the alkoxide groups are removed by the acid- or
