Development of a Conducting Polymer [polyaniline] based gas sensor

Development of gas sensors to monitor combustible gases is imperative due to the concern for safety requirements in homes and industries. The liquefied petroleum gas (LPG)/ NH3 is one of extensively used but potentially hazardous gases and its detection is particularly important, because explosion accident may be caused when it leaks out accidentally or by mistake. Most of the commercially available sensors are made up of metal oxides which operate only at high temperature (about 200°C), and hence need an adjacent system for heating, leading to higher power consumption. Hence need is for a use and throw sensor low power consuming sensor. In comparison to the above a sensor made of conducting polymer has many improved characteristics; such as higher sensitivity, short response time, ability to operate at room temperature. The conducting polymers offer unique combination of electrical, mechanical and physical properties in the fabrication of devices. Presented in this paper is an effort to develop polyaniline, a conducting polymer based gas sensor and a proof of concept integrated sensor system. Conventionally gas sensors have been made using metal oxide such as Sn02, and Zn0, which require high temperatures for sensing and thus result in high power consumption. The current work is an effort towards developing polymer based sensor system for odour detection. Conducting Polymers are better suited for sensing purposes as they have the advantage of sensing at room temperature. They ability to fabricate these Thin Film sensors and on flexible substrates gives them an edge. This paper discusses the synthesis of a conducting polymer Poly Aniline for detection of gases such as LPG, H2S and NH3. The chemical and electrical properties were then studied. Measurements were then repeated to establish reproducibility of the material. The detailed process and properties report is presented in the paper. A representative sensor an- a complete signal condition processing system to ascertain the system was also developed for a sample with a room temperature conductivity of 1.54 S/cm. The system was tested for its ability to sense ammonia and LPG gases.