Nanomaterials in humidity sensors

Nanomaterials have gained significant importance recently due to their unique characteristics like high porosity, large specific area, hollow surfaces, hydrophilic groups, high surface charge density, nanoscale channels, and extra binding sites. These characteristics play a vital role in various sensing applications, but this work is mainly designed to showcase the impact of nanomaterials on humidity sensors. Various humidity sensors (resistive, capacitive, impedimetric, optical, and self-powered) have been reported using nanomaterials (0-D, 1-D, 2D, and 3-D). These nanomaterial-based humidity sensors have shown promising characteristics, including short response/recovery time (0.2/0.3 seconds), high sensitivity (107%), long lifetime (6 months), wide range (0%–100%), and low hysteresis (0.25%). This book chapter will cover the advancement of nanomaterial-based humidity sensors with a comprehensive analysis of their physiochemical and structural properties. Conduction mechanisms responsible for adsorbing/desorbing water molecules and their interaction with the surface of nanomaterials are also included.