Biomedical Engineering Reference
In-Depth Information
Electrochemical polymerization at low and constant current levels
was used to fabricate 10 nanoframework-electrode junctions
simultaneously with uniform diameter (ca. 40 to 80 nm) PANI
nanowires intertwined to nanoframeworks. Electropolymerization
was carried in an aqueous solution containing 0.5 M aniline and
1.0 M HCl. First, a constant current (50 nA) was applied for ca.
30 min to introduce the PANI nuclei onto the Pt working junction
electrodes. The current was then reduced to 25 nA for 180 min.
The PANI nanoframeworks begin to propagate from the working
junction electrodes to the other set of the junction electrodes.
In the last step, the current was decreased to 12 nA for 180 min,
and the 10 polyaniline nanoframework-electrode junctions
were obtained simultaneously with each PANI nanoframework
positioned precisely within the 2 μm gap between its electrodes.
All these nanoframework electrode junctions can be covered by
such conducting polymer wires simultaneously and site-specifically
in a parallel fashion. This device can be used as miniaturized
resistive sensors for real-time detection of NH3 and HCl gases. Such
two-terminal devices can be easily converted to three-terminal
transistors by simply immersing them into an electrolyte solution
along with a gate electrode. Electrolyte-gated transistors based on
conducting polymer nanowires junction arrays was developed and
the field-induced modulation can be applied for signal amplification
to enhance the device performance [124]. Conducting polymer
nanowires, including PANI (ca. 50-80 nm), Polypyrrole (PPy) (ca.
60-120 nm), and poly(3,4-ethylenedioxythiophene) (PEDOT) (ca.
80-150 nm), were introduced to the 10 paralleled 2-μm-wide gaps
by the template free electropolymerization method. The preparation
of electrolyte gated transistors can be completed simply immersing
the conducting polymer nanowire-based two-terminal resistive
device along with a gate electrode (a Pt wire or Ag/AgCl electrode)
into a buffered electrolyte solutions containing NaCl. P-channel
transistor characteristics at pH 7 and n-type behavior in basic media
were observed for both PANI and PPy nanowires, whereas PEDOT
nanowire-based device only exhibit depletion mode behaviors in
neutral solutions. These open new opportunities to fabricate
sensor arrays with conducting polymer nanowires to realize
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