Inkjet-printed polypyrrole thin films for vapour sensing

Inkjet-printed films of the conductive polymer polypyrrole have been used for vapour sensing at room temperature. The electrical properties, sensitivity, reproducibility and stability of the polymer chemiresistors are reported. A significant increase in conductivity was observed on the exposure of the films to the vapours of simple alcohols. The value of the fractional resistance change, ΔR/R, of the films increased linearly with increasing concentrations of both ethanol and methanol. A relatively high ΔR/R value, approximately 90%, was obtained on exposure to 5000 parts per million of methanol. The response time of the inkjet-printed sensors to polar vapours was generally shorter than that for non-polar compounds. It is suggested that the increase in conductivity may be related to a vapour-induced change in the transfer of charge carriers between the polymer chains.