Graphene and Its Nanocomposites Based Humidity Sensors: Recent Trends and Challenges

Abstract

Humidity sensors are of utmost importance in certain areas of life, in processing industries, in fabrication laboratories and in agriculture. Precise evaluation of humidity percentage in air is the need of various applications. Graphene and its composites have shown great potential in performing as humidity sensors owing to enormous surface area, very low electrical noise, high electrical conductivity, mechanical and thermal stability and high room temperature mobility. There is no such extensive review on graphene-based devices for humidity sensing applications. This review extensively discusses graphene-based devices intended towards sensing humidity, starting from the methods of synthesizing graphene, its electronic and mechanical properties favoring sensing behavior and different types of sensing mechanisms. The review also studies the performance and recent trends in humidity sensor based on graphene, graphene quantum dots, graphene oxide, reduced graphene oxide and various composite materials based on graphene such as graphene/polymer, graphene/metal oxide or graphene/metal. Discussions on the limitations and challenges of the graphene-based humidity sensors along with its future trends are made.

Ultra-Sensitive and Fast Humidity Sensors Based on Direct Laser-Scribed Graphene Oxide/Carbon Nanotubes Composites

“…Recently, a wide spectrum of materials, material hybrids, and composites have been developed based on different kinds of principles such as paper-based [13], cellulose composites [14], metal oxides [15,16], nanoparticle [10], metal-organic framework [17]. Among widely studied materials for humidity measurement are graphene and its derivatives, especially graphene oxide (GO), using different sensor principles [5,[18][19][20] with high sensitivity and fast response times.…”

Development of a Smart and Ultrafast Flexible Humidity Sensor Using the 0D/2D Au/GeS Heterostructure for Human Respiration Rate Monitoring

“…19−21 Apart from their application in breath rate detection, the utilization of humidity sensors has been expanded in building ventilation control, weather forecasting, paper manufacturing, chemical gas purification, and smart agriculture monitoring as well. 22,23 Therefore, the increasing demand for humidity sensors in various IoT applications encourages the development of sensors with excellent sensing characteristics such as high response, fast response/recovery kinetics, a wide humidity detection range, high stability, and repeatability. In this respect, microbalance, and optical fiber technology.…”

“…The chemiresistive humidity sensor works as a transducer that responds to the water molecule's adatoms by showing a rapid change in electrical conductivity/resistance with negligible electrical noise. 23 With such interests, chemiresistive humidity sensors have been developed by exploiting traditional bulk materials (polymers, metal oxide, ceramics), nanomaterials (nanowires, carbon nanotubes, nanodots), and their nanocomposites. 25,26 However, the humidity sensors, so far reported, suffer from major problems in terms of stability, robustness, slow sensor dynamics due to surface poisoning, hysteresis effect, and a limited range of relative humidity (RH) sensing.…”

“…Additionally, fabrication of pressure sensors, optical breathing sensors, and CO 2 measurement devices is worth mentioning. Identifying the differences in humidity content during the inhalation–exhalation cycles is another effective approach to monitor the respiration rate. , Indeed, humidity is a vital observable in human breath, and by the utilization of ultrafast humidity sensors, accurate monitoring of the respiration rate is possible. − Apart from their application in breath rate detection, the utilization of humidity sensors has been expanded in building ventilation control, weather forecasting, paper manufacturing, chemical gas purification, and smart agriculture monitoring as well. , Therefore, the increasing demand for humidity sensors in various IoT applications encourages the development of sensors with excellent sensing characteristics such as high response, fast response/recovery kinetics, a wide humidity detection range, high stability, and repeatability. In this respect, humidity sensors are developed by exploiting different transduction mechanisms such as a change in resistance or capacitance, quartz crystal microbalance, and optical fiber technology .…”

“…Many research efforts have been devoted to exploring resistivity-based flexible humidity sensors, benefiting from their easy fabrication, simple sensing mechanism, miniaturization, low power consumption, autonomous working, and the feasibility of integrating with wearable devices toward emerging IoT. The chemiresistive humidity sensor works as a transducer that responds to the water molecule’s adatoms by showing a rapid change in electrical conductivity/resistance with negligible electrical noise . With such interests, chemiresistive humidity sensors have been developed by exploiting traditional bulk materials (polymers, metal oxide, ceramics), nanomaterials (nanowires, carbon nanotubes, nanodots), and their nanocomposites. , However, the humidity sensors, so far reported, suffer from major problems in terms of stability, robustness, slow sensor dynamics due to surface poisoning, hysteresis effect, and a limited range of relative humidity (RH) sensing. , These sensors show a highly nonlinear electrical response in the case of high exposure to humidity (>80% RH) and also offer a little change in response in ultra-dry atmospheres (<20% RH) as the signal-to-noise ratio (SNR) drastically decreases.…”