Polyaniline based impedance humidity sensors

In this study, the fabrication and sensing response of humidity sensor based on the polyaniline (PANI) thin film have been studied. PANI thin films with 30–70 μm thickness were deposited on glass substrates between pre-deposited silver and gold electrodes. It was found that the sensing mechanism is based on the impedance and capacitance variations. For change in Relative Humidity (RH) from 36 to 90%, the change in sensor's capacitance and impedance is 167 and 471 times, respectively. The impedance–humidity relationship is more uniform as compared to capacitance–humidity relationship for this range of humidity. It is also observed that annealing enhanced the sensitivity of the sensor by two times. The consequence of measuring frequency and absorption–desorption behavior of the humidity sensor are also discussed in detail. Response (τres) and recovery (τrec) times are 8 and 27 s respectively. Results are examined by simulation and found in good agreement with experimental data.

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► Humidity sensors based on polyaniline films are fabricated and investigated.
► Impedance–humidity relationship is more linear as compared to capacitance–humidity.
► Absorption and desorption curves are coincided with an experimental error of ±2%.
► Response and recovery times are 8 and 27 s respectively.
► Simulation is in good agreement with experimental results.