A high-performance flexible humidity sensor based on a TiO₂-MWCNT nanocomposite for human healthcare applications

The present work shows the improved humidity sensing characteristics of TiO₂ nanoparticles in the form of a nanocomposite with multiwalled carbon nanotubes (MWCNTs) prepared by a hydration-dehydration method. The structural and morphological characterizations of TiO₂-MWCNTs confirm the nanocomposite formation without any other impurities and with an improved surface area. The pure TiO₂ and nanocomposite films are deposited on IDE coated flexible poly-ethylene terephthalate (PET) substrates by a drop casting method. The nanocomposite shows improved sensitivity (1246.2 MΩ/%RH) and an ultrafast response/recovery time (2 s/1 s) with a minimal hysteresis of 0.27%RH. Further, the flexible nanocomposite sensor is tested for human healthcare applications including respiratory monitoring, apnea like situations, and skin moisture detection. The sensor can distinguish different breath patterns like normal, fast, deep and apnea like situations significantly. Skin moisture detection can also be performed using the nanocomposite sensor in a non-invasive manner. Overall, this study represents an environmentally friendly, easy to fabricate, flexible TiO₂-MWCNT nanocomposite based improved humidity sensor for application in human healthcare and wearable devices.