Novel, self-organising materials for use in gas sensor arrays: beating the humidity problem.

Research into volatile sensing using arrays of conductive polymer sensors has identified two significant problems: namely, sensitivity to water vapour and poor sensitivity to hydrocarbons and other hydrophobic molecules. For instance, the humidity responses of conductive polymer sensors are sometimes so high that the small signals produced by important volatiles are lost, leading to a lack of discrimination. In this paper we present a number of alternative materials for use in chemoresistive gas sensor arrays. They are based upon discotic liquid crystals. Discotic liquid crystals show no or very little sensitivity towards water vapour but show resistance changes of up to 90% on exposure to various volatiles and in addition they are sensitive to hydrocarbons. A relationship between carbon chain length for normal alkane hydrocarbons and the resistance change of the discotic liquid crystal can also be seen. (C) 1998 Elsevier Science S.A. All rights reserved.