Humidity sensor based on ultrathin polyaniline film deposited using layer-by-layer nano-assembly

In this paper, we use layer-by-layer (LbL) nano-assembly for deposition of ultrathin poly(anilinesulfonic acid) (SPANI) films for fabrication of highly sensitive and rapid response humidity sensors. Spin coating was also used for fabrication of SPANI based humidity sensors for comparison. The change in electrical sheet resistance of the sensing film was monitored as the device was exposed to humidity. For 5% change in relative humidity, the sensitivity was measured to be 11 and 6% from layer-by-layer based and the spin coated humidity sensors, respectively. An intended application for these layer-by-layer assembled devices is in disposable handheld instruments to monitor the presence of humidity in humidity sensitive environments.