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.

In this paper, we present a comparative study of Graphene Oxide (GO) and chemically reduced Graphene Oxide (rGO) based resistive type humidity sensors fabricated on Ti/Au Inter-Digital Electrodes (IDEs) coated SiO2 substrates. The sensing performance, including sensitivity, response/recovery time, and hysteresis has been evaluated for both sensors. The GO film exhibited quick response (0.3 s) and high sensitivity (104.7 kΩ/%RH) with remarkable repeatability and negligible hysteresis as compared to rGO film sensor. The excellent humidity sensing properties of GO are attributed to the presence of abundant oxygen-containing polar functional groups on GO relative to rGO. To demonstrate the multifunctional applications of developed GO based sensor, we have also demonstrated its use as respiratory monitoring, non-contact proximity detector, and speech event detector through the detection of humidity perturbations. The work suggests GO sensitive material has high potential for the development of wearable and integrated health monitoring platforms and non-contact sensing devices.

In the present paper, we studied SnO2 nanostructured thin film-based resistive type humidity sensor fabricated by spin coating method on alumina substrate and showed its application in real time respiratory monitoring. Experiments show the growth of crystalline SnO2 nanoparticles with a tetragonal phase, with an average particle size of-15 nm and a high surface roughness of the order of 50-60 nm. The gold-interdigitated electrodes were patterned on the SnO2 film surface by DC sputtering technique to study the sensing response of the film. The sensor shows a high sensitivity of 1.34 k & omega;/%RH, a minimal hysteresis of 0.94%, and good repeatability. The developed sensor is tested for monitoring human breath patterns in different physical conditions, and apnea like situations, which suggests its potential for clinical applications. Overall, the present work proposes an envi-ronmental friendly, easy-to-synthesize, highly stable, and simple facile SnO2 based deployable humidity sensor to diagnose human health patterns in a non-contact manner.

We report a sustainable resistive-type humidity sensor based on chitosan (CS) film deposited on an interdigitated Ti/Au electrode coated SiO2 substrate using a simple drop cast approach for human health monitoring. The sensor revealed remarkably high sensitivity (5.8 MΩ/%RH), fast response/recovery time (21 s/25 s), low hysteresis (∼9.3%), excellent reversibility, wide detecting range (11–95% RH), and high selectivity toward water vapor. The calculated associated uncertainty at different %RH indicates the excellent repeatability and stable performance of the sensor. The developed sensor is tested for different human breath patterns, and it is found that the sensor can clearly distinguish between the variations in rate and depth of respiration patterns during normal, fast, deep, and nasal breathing and can monitor for apnea-like situations. The sensor is also utilized to perform noncontact skin humidity sensing. Overall, the developed CS film humidity sensor provides a viable approach for the detection of respiratory disorders and human health issues, detected by skin moisture, in a noninvasive manner.