Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation (LPE) followed by Langmuir-Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.
@article{arxiv.2009.14517,
title = {Ultrafast humidity sensor based on liquid phase exfoliated graphene},
author = {Stevan Andrić and Tijana Tomašević-Ilić and Marko V. Bošković and Milija Sarajlić and Dana Vasiljević-Radović and Milče. M. Smiljanić and Marko Spasenović},
journal= {arXiv preprint arXiv:2009.14517},
year = {2020}
}