Biomedical Engineering Reference
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spacing) containing a simple monolayer of lying cylinders. Park
et al.
-PMMA copolymer
film on a Si substrate first coated with a thin, thermally evaporated
Ag layer [57]. The resulting template (PMMA UV photodegraded, or
alternatively P2VP selectively dissolved) was used as a mask to guide
the electrochemical etching (0.7 V vs Pt counterelectrode in 1%
demonstrated this approach with a P2VP-
b
vol
HNO
) of the exposed Ag substrate (Fig. 2.10). Electrodeposition
rather than etching could of course be used to produce conducting
or semi-conducting wires in a similar manner.
3(aq)
(a)
(b)
Electrochemical fabrication of in-plane nanowires. (a) 27 nm
thick porous PS-
Figure 2.10
-PVP template after selective dissolution of PVP in ethanol.
(b) Masked electrochemical etching of Ag silver nanowires produced from
the template in (a). Scale bar 200 nm. Reproduced with permission from
Ref. [57]. Copyright Wiley-VCH Verlag GmbH & Co. KGaA.
b
2.4.4.2 Standing nanowires arrays
Templating vertical nanowire arrays is generally more challenging
than in-plane wires since the cylindrical microphase must first be
persuaded to stand vertically on the substrate (see Section 2.3.1)
to produce film-spanning porosity on removal of the minority
domains. The method of applying an electric field across a substrate-
supported film devised by Thurn-Albrecht
remains the most
reliable: the copolymer film is incorporated into a simple parallel-
plate capacitor geometry while heating above the glass transition
temperature of both constituent blocks (shown schematically in
et al.
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