Biomedical Engineering Reference
In-Depth Information
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FIGURE 4.2
Schematic of nanowires-based detection. Nanowire device modified with antibodies (
Left
). Specific binding of
targets on the nanowires produces a response change (
Right
) characteristic of the surface charge of the targets on
the nanowire. When the target unbinds from the surface, the response return to the baseline value.
from different laboratories and discuss how we have attempted to address these limitations.
We then continue to discuss the functionalization and assembly of these 1-D nanostructures.
We demonstrate how they have been used for label-free detection of various biological mole-
cules and how such devices have enabled the achievement of extremely high sensitivity and
low detection limits. Finally, we conclude by highlighting some of the challenges we face in
the 1-D nanostructured materials research arena and also predict the direction toward which
future research on this area might be directed.
4.2
Fabrication of One-Dimensional Conducting Polymer Nanostructures
The ability to synthesize, pattern, and write conducting polymers (CPs) is one of the tar-
get areas for fabrication of organic electronic devices. Several techniques such as photo-
chemical lithography [8,9], micromoulding [10], electropolymerization using modified
electrodes [10], deposition using scanning electrochemical microscopy [11], and printing
techniques [12] have been successfully applied to fulfill the micrometer and submicrome-
ter dimension. There is, however, increased demand for miniaturization of CPs to the
nanometer scale. Among the methods that have been used to fabrication CPs to the
nanometer scale are electrochemical dip-pen lithography, mechanical stretching [13], elec-
trospinning [14,15], and polymer-templated electrochemical synthesis [16].
4.2.1
Dip-Pen Nanolithography
Invented by Mirkin and coworkers, Dip-Pen nanolithography (DPN) is a scanning probe
nanopatterning technique in which an atomic force microscopy (AFM) tip is used
