Biomedical Engineering Reference
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can be completely removed in an etching process, which leaves the
second component mechanically sound, acting as a self-supporting
mesoporous matrix. Second, the pore structure left by etching must
span the full thickness of the template from surface to substrate,
such that any electrolyte flowing into the pores is able to achieve
electronic contact with an underlying working electrode. That
relatively few further examples of high-aspect-ratio electrochemical
BCP replication exist owes much to the difficulties in satisfying this
condition. The following discussion is, therefore, largely dedicated
to describing important aspects of porous template formation in
diblock copolymers — the characteristics of thin film self-assembly,
microphase alignment techniques, selective degradation, and
suitability to large area electrochemical replication. Progress in
the patterning of standing and lying nanowire arrays and recent
replication of spontaneously bicontinuous networks using this
technique are reviewed. Finally, the first application of such highly
ordered nanostructures in functioning photovoltaic devices is
described in nanostructured solar cells based on electrochemically
synthesized titanium dioxide arrays.
bcp phase
separation
porous template
templated
functional array
freestanding
array
functional
material junction
Counter electrode
Ref
~ 10 nm
electrochemically
synthesized material
V
Conducting substrate
polymer
matrix
Figure 2.1
Schematic process of templating porous materials, highlighting
the film-based electrochemical replication of a porous template in a
standard electrochemical cell.
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