When considering new sensory technologies one should look to nature for guidance. Indeed, living organisms have developed the ultimate chemical sensors. Many insects can detect chemical signals with perfect specificity and incredible sensitivity. Mammalian olfaction is based on an array of less discriminating sensors and a memorized response pattern to identify a unique odor. It is important to recognize that the extraordinary sensory performance of biological systems does not originate from a single element. In actuality, their performance is derived from a completely interactive system wherein the receptor is served by analyte delivery and removal mechanisms, selectivity is derived from receptors, and sensitivity is the result of analyte-triggered biochemical cascades. Clearly, optimal artificial sensory sys-

Conjugated polymer-based chemical sensors.

‘Polyaniline’: Protonic acid doping of the emeraldine form to the metallic regime

Progress in preparation, processing and applications of polyaniline

Color Control in π-Conjugated Organic Polymers for Use in Electrochromic Devices

Application of conducting polymers to biosensors.

: Anodic growth of polyaniline films on a Au microelectrode array has been carried out to add to the characterization of polyaniline and to fabricate polyaniline-based microelectronic devices, diodes and transistors, that function when the polyaniline-functionalized microelectrode array is immersed in an electrolyte solution. The microelectrode array is a set of eight Au electrodes, 0.1 micrometer thick, 4.4 micrometers wide and 50 micrometers long, each individually addressable and separated from each other by 1.7 micrometers. Polyaniline can be deposited in controlled amounts by electrochemical oxidation of aniline. When the polyaniline is deposited in sufficient amounts, two or more of the eight Au microelectrodes can be connected in the electrical sense. Current can pass between two connected microelectrodes when there is an applied potential between them. The magnitude of the current at a given applied potential depends on the electrochemical potential of the polyaniline. In 0.5 M NaHsSO4/H20 the current (at a fixed applied potential) is maximum at an electrochemical potential of approx. +0.4 V vs. SCE and declines by a factor of greater than 1,000,000 upon reduction to +0.1 or oxidation to +0,7 V vs. SCE. Owing to the large change in resistance upon change in electrochemical potential, the functionalized microelectrodes is crucial to device function, owing to the limited conductivity of the polyaniline. The switching time of a transistor-like device is faster than 0.1 s.

/pdf/resistance-of-polyaniline-films-as-a-function-of-hy6h0chvwy.pdf

Elizabeth W. Paul

Papers

Resistance of Polyaniline Films as a Function of Electrochemical Potential and the Fabrication of Polyaniline-Based Microelectronic Devices.