Graphene for IoT Applications

Graphene is one of the most versatile materials discovered on the planet and is promised to impact a large number of areas. It has many unique properties like stable chemical and mechanical behaviour, very good heat and electrical conductivity and it is extremely lightweight and the strongest material. It is these amazing properties of the material that has attracted attention of many research groups around the globe.

In January 2018 a research group from University of Manchester had published a paper in Nature Journal where they have proposed a graphene based sensor for wireless application and they claimed that it could pave way for many efficient sensors for wireless applications.

The wireless sensor this research developed is a battery less wireless humidity sensor. Their sensor works on the principle that relative dielectric permittivity of graphene oxide (GO) increases with humidity at GHz frequency range, as GO is a hydrophilic material. GO is capable of absorbing significant amount of water and its water absorption depends strongly on the humidity of the environment. The wireless functionality in the sensor is obtained by coating printed graphene RFID antenna with the layer of graphene oxide. Working of the sensor is explained from the Figure 1.

Figure 1: Working of GO based Humidity Sensor (Source: Ref 1)

GO is coated on the RFID printed graphene antenna. The backscattering signal from the sensor is read by the RFID reader and this backscattering is proportional to humidity in the atmosphere. RFID reader transmit the forward electromagnetic wave signal to RFID graphene antenna and energises it. The backscattering signal from the antenna is both phase and amplitude modulated and gives a measure of humidity in the environment. Actually the antenna is sensitive to proximity effect i.e. its resonance frequency and phase is sensitive to its surrounding. In this case having a GO coating on the antenna makes antenna sensitive to humidity in the environment.

The sensor is fully portable, printable and battery less and these properties make it ideal of remote monitoring in IoT applications. Moreover sensors like this could be mass produced very economically and can be scaled up very fast. As we know that IoT system should dependably contain battery less sensors with RFID enablers. Therefore this one development of humidity sensor could open avenues for a large number of IoT applications using graphene based sensors

Ms. Manisha Aggarwal - Asst. Professor (ECE), Chitkara University, H.P.

References

1. Xianjun Huang et al. Graphene Oxide Dielectric Permittivity at GHz and Its Applications for Wireless Humidity Sensing, Scientific Reports (2018). DOI: 10.1038/s41598-017-16886-1