An electronic tongue using polypyrrole and polyaniline

An electronic tongue composed of six different sensing units: a bare interdigitated electrode, and interdigitated electrodes coated with stearic acid (SA), a polyaniline oligomer (16-mer), polypyrrole (PPy) and mixtures (1:1, w/w) of 16-mer/SA and PPy/SA, was able to distinguish salt, sweet, bitter and acidic solutions. The films were deposited by the Langmuir–Blodgett (LB) technique onto interdigitated electrodes, and impedance studies were performed over the frequency range 20–105 Hz. The sensor is able to distinguish between different brands of mineral water, tea and coffee and can also differentiate tastants below the human detection threshold, proving that conducting polymers are useful sensing materials and transducers for this sort of application.