Biomedical Engineering Reference
In-Depth Information
electrodeposited by the same strategy [80]. They were first prepared
by electrodepositing nanowires of a conductive metal oxide such
as NiO, Cu
2
. Nanowires of the parent metal were then
obtained by reducing the metal oxide nanowires in hydrogen at
an elevated temperature. Nanowires with diameters in the range
15 nm to 750 nm were obtained by electrodeposition onto the step
edges present on the surface of highly oriented pyrolytic graphite
electrode. After embedding the nanowires in a polymer film, arrays
of nanowires could be lifted off the graphite surface, thereby
facilitating the incorporation of these arrays in devices such as
sensors. Vertical arrays of metal nanowire hold promise for making
chemical and biological sensors in addition to electron emitters
in field-emission displays. The difficulty of growing well-defined
arrays has kept these technologies at bay. However, electrochemical
nanofabrication using crystalline protein masks solved such
problem [82]. A simple and robust method was developed to
fabricate nanoarrays of metals and metal oxides over macroscopic
substrates using the crystalline surface layer (S-layer) protein of
deinococcus radiodurans
O, and MoO
2
as an electrodeposition mask. Substrates
are coated by adsorption of the S-layer from a detergent-stabilized
aqueous protein extract, producing insulating masks with 2-3 nm
diameter solvent-accessible openings to the deposition substrate.
The coating process can be controlled to achieve complete or
fractional surface coverage. The general applicability of the
technique was demonstrated by forming arrays of Cu
O, Ni, Pt,
Pd, and Co exhibiting long-range order with the 18 nm hexagonal
periodicity of the protein openings. This protein-based approach
to electrochemical nanofabrication should permit the creation of a
wide variety of two-dimensional inorganic structures.
2
1.4 ELECTROCHEMICAL NANOLITHOGRAPHY
In addition to its well-known capabilities in imaging and spectroscopy,
scanning probe microscopy (SPM) has shown great potentials for
patterning of material structures in nanoscales with precise control
of the structure and location. Electrochemical nanolithography
using SPM, which includes scanning tunneling microscopy (STM)
and atomic force microscope (AFM), has been used to fabricate
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