Gas sensing and biosensing applications of conducting organic polymers

Discusses recent progress in the design of gas and odour sensors based on conducting organic polymers and the applications of these materials towards the design of new biosensors using enzymes. Polymers of a number of heterocyclic compounds display physico-chemical characteristics which cause them to behave as semiconductors. Adsorption of polar chemicals on the surfaces can cause reversible changes in DC conductivity at ambient temperatures. The author has produced arrays of twenty different sensors occupying a total area of 1 cm². A small microprocessor based circuit continually monitors the resistance of each sensor in the array at a rate of 20 Hz. Each sensor element changes in resistance when exposed to a polar volatile compound and though somewhat dependent on the nature of the compound and its concentration, usually about three measurement cycles of adsorption/desorption can be carried out per minute. Responses are observed within about 100 ms, and if the concentration of gas or odour is constant, the DC conductance of the polymers remains constant until the volatile is removed. Desorption times vary from 10 s to 1 min depending on the particular chemical being sensed. The data are transferred through a serial interface to an IBM-compatible computer for data processing and pattern recognition. The sensors are not poisoned by chemicals which destroy metal oxide, platinum silicon, or pthalocyanine based semiconductor gas sensors