Nanoengineered Conductive Polyaniline Enabled Sensor for Sensitive Humidity Detection
Samar S. Sandhu, Saurabh Kumar, Shine Augustine, Udiptya Saha, Kamal Arora, Sayan Bayan, S. K. Ray, Nitin K. Puri, Bansi D. Malhotra
Abstract
We report results of the studies relating to the fabrication of a paper-based humidity sensing element comprising a nanostructured polyaniline (PANI) coating on a filter paper substrate. The electrical conductivity of the PANI integrated conductive paper increases from 1.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> Scm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> to 1.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> Scm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> on modification of the polymerization protocol. This increase in conductivity is ascribed to the change in morphology of the PANI coating from nanogranular (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) to partially nanofibrous (pN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ). We investigate the effect of observed morphologies of PANI-paper composites on their resistive-type humidity sensing performances. The partially nanofibrous (pN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ) PANI-paper exhibits a bimodal humidity response due to polymer-swelling effect at higher humidity (≥ 55% RH). However, the nanogranular (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) PANI-paper yields a unimodal, linear humidity response within the humidity range, 16-96.2% RH, with a sensitivity of 9.79 kΩ/% RH (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ≈ 0.996). Hence, the N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> PANI-paper is a promising alternative to the conventional humidity sensors fabricated on ITO glass/bare glass/PET substrates.