Integration of Graphene Oxide with Resonant RF Structures for Wireless Humidity Sensing

The exponential progression of the fourth industrial revolution has transformed the way in which individuals live and work on the Internet of Things (IoT) era. At the heart of IoT is the concept of wireless sensing, a key facilitator for data-driven decisions in autonomous systems and the digitization revolution. Many traditional sensors rely on resistive and capacitive changes to sense environmental makers for which DC conductivity is often measured and the data are then transmitted through additional external communication circuitry. This research employs Radio Frequency (RF) technology, which epitomizes a contemporary advancement in sensor design and allows wireless sensing without external circuitry. Here, we employ a two-dimensional (2D) derivative to graphene which is functionalized with oxygen to yield graphene oxide (GO) membranes, as a sensing material to measure environmental changes in ambient humidity. An RF copper antenna was fabricated on oxidized Silicon substrates which serves as a wireless transmitter, while hydrophilic GO atop the copper antenna serves as a dielectric medium. Due to its hydrophilic nature, GO changes its dielectric permittivity as the ambient humidity changes in the environment, which in turn alters the overall dielectric property of the device and shifts the resonance frequency of the antenna-GO ensemble. We show that the return loss of the antenna-GO ensemble serves as a means to measure environmental humidity and quantify its sensing behavior.