Ultrafast humidity sensor based on liquid phase exfoliated graphene

• Published in: Nanotechnology 2021-01, Vol.32 (2), p.025505
• Main Authors: Andri, Stevan, Tomaševi -Ili, Tijana, Boškovi, Marko V, Sarajli, Milija, Vasiljevi -Radovi, Dana, Smiljani, Mil e M, Spasenovi, Marko
• Format: Article
• Language: English
• Subjects: graphene; humidity sensing; liquid phase exfoliation; respiration monitoring
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/abb973

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 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.