Biomedical Engineering Reference
In-Depth Information
Complete filling of the template was acheived in a standard
manner by monitoring the electrochemical cell current under
potentiostatic operation as shown in Figs. 2.22 and 2.23.
Electrochemical replication of gyroid templates can be extended
to rather thick layers (in comparison to the characteristic unit cell
dimension); the network voids retain uniform porosity from the
film surface to the underlying substrate for arrays at least several
microns thick. The remarkable continuity of the network through
thick template layers is seen in Fig. 2.24, showing the cross section of
a ∼4 μm thick replicated network. Clearly the array grows uniformly
through the template, and grains of ∼1 μm are visible, with complete
connectivity. The implication is that all parts of the pore network
are in electrical contact with the underlying substrate throughout
replication. By extension, the template matrix phase is also fully
continuous, so that any material later infiltrated into the array will
have complete access to every part of the network.
Figure 2.24
SEM image of thick gyroid template replication in TiO
.
2
A ∼
array demonstrates that the gyroid template remains
fully porous in much thicker films, enabling deposition of thick arrays which
grow uniformly upward from the underlying substrate. Reproduced with
permission from Ref. [61].
4
μm thick TiO
2
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