Graphene oxide-based humidity sensors

Humidity sensors or hygrometers are the devices adopted for the measurement of humidity in its surrounding environment. Various materials have been designed and utilized for the fabrication of different humidity sensors including planar and flexible devices. Among these materials, graphene oxide (GO) and its compounds or alloys has received great attention as an active or sensing element for humidity sensors development because of oxygen-consisting functional groups, unique mechanical properties, easy processability, and tunable physical properties. Recent developments in humidity-sensors technology show that the sensor devices fabricated with graphene oxide possess excellent time of response and time of recovery along with immense stability and durability. In this view, the chapter starts with a brief history of humidity sensors, materials used for their development, and different types of humidity sensors. Then, the graphene oxide basic properties, synthesis, characteristics, and applications are discussed. Finally, fabrication of humidity sensors using GO, testing, and mechanism along with characteristics of different humidity sensors are discussed in detail.