Researchers have a design that layers graphene oxide, to create flexible heterostructure humidity sensors for remote sensing.
* layer by layer printing allows for scalable and mass production at a very low cost.
* the first printable technology where several 2D materials combine to create a functional device immediately suitable for industrial applications.
* No battery source is neeeded as it harvests power from the receiver, making it more than ideal for the internet of things (IoT)
The relative dielectric permittivity of graphene oxide (GO), both its real and imaginary parts, have been measured under various humidity conditions at GHz. It is demonstrated that the relative dielectric permittivity increases with increasing humidity due to water uptake. This finding is very different to that at a couple of MHz or lower frequency, where the relative dielectric permittivity increases with decreasing humidity. This GO electrical property was used to create a battery-free wireless radio-frequency identification (RFID) humidity sensor by coating printed graphene antenna with the GO layer. The resonance frequency as well as the backscattering phase of such GO/graphene antenna become sensitive to the surrounding humidity and can be detected by the RFID reader. This enables battery-free wireless monitoring of the local humidity with digital identification attached to any location or item and paves the way for low-cost efficient sensors for Internet of Things (IoTs) applications.