A smart functional surfactant activated conductive polymer coated on paper with ultra-sensitive humidity sensing characteristics

Abstract

Herein, surfactant-assisted PANI nanorods were synthesized via the solid-state synthesis method at different concentrations of sodium lauryl sulfate (SLS). Upon the addition of SLS, the average rod diameter of PANI decreased from 72 ± 6 nm to 58 ± 6 nm. The electrical conductivity of PANI increased three-fold upon the addition of SLS (8.2 S cm⁻¹). Furthermore, the presence of SLS modulated the PANI chains, which facilitated the enhancement of the thermal stability. A PANI/SLS-based humidity sensor was built on a paper substrate through the doctor blade coating technique and its performance metrics were accessed under different humidity conditions. The PANI/SLS coated paper-based humidity sensor exhibited excellent response along with fast response/recovery characteristics. SLS assisted PANI nanorods having an improved electrical conductivity and high surface area readily interacted with water molecules, which significantly increased the sensitivity of the sensor up to 31.5 kΩ/%RH (linearity = 0.99). Furthermore, the sensor showed excellent response under physiological conditions such as respiration monitoring and skin moisture detection. The ultrasensitive humidity sensing performance of PANI/SLS coated paper with good skin-friendly characteristics makes it a potential material for multipurpose smart wearable devices.