Three Types of Films from Liquid-phase-exfoliated Graphene for Use as Humidity Sensors and Respiration Monitors

Abstract

Measuring relative humidity is important for a myriad of industries, including production, agriculture, environmental monitoring, and medicine. Thin-film, fast-response sensors are particularly interesting for wearable applications, such as monitoring breathing. We report on humidity sensors made from graphene deposited as a thin film by the Langmuir–Blodgett (LB) method from three types of graphene in solution. We demonstrate humidity sensing and respiration monitoring from graphene made by bath sonication, probe sonication, and electrochemical exfoliation. We characterize the morphology and chemical composition of the three film types and compare their performance as sensors. We conclude that although all three types can be used for sensing, they each have their particular advantages and drawbacks.