Reduced Graphene oxide-based sustainable ink formulations and their implementation in screen-printed graphene field effect transistors and humidity sensors development

The Internet of Things (IoT) has revolutionized the requirements for sensors and smart devices, where high performance, power efficiency and low manufacturing costs are mandatory. As a consequence, the research for better performing materials and more cost-effective manufacturing techniques is being performed. This work reports on ink formulations based on nitrogen-doped graphene and environmentally friendly polymers (Polyvinylpyrrolidone (PVP) and Carboxymethyl cellulose (CMC), and their use in fully screen-printed transistors and humidity sensors. The ink formulations were developed using environmentally friendly solvents and showed non-Newtonian behaviour. The N-rGO composites showed a high electrical conductivity of 1.9 ± 0.5 S∙cm −1 , 100 times higher than the reduced graphene oxide (rGO) composites. Fully printed Graphene field effect transistors (GFET) were developed with low operating voltage of < 2 V to be implemented as humidity sensors with the fully a linear response and high sensitivity (4.25 Ω∙%RH −1 as resistive sensor), allowing integration into low-power microcontrollers for sensing applications. • Reduced graphene oxide-based inks were formulated and optimized for screen-printing using different sustainable binders. • The developed inks were used on flexible screen-printed graphene field effect transistors with low operating voltage (±2 V). • Humidity sensors with fast response (<2 s) and high sensitivity up to 65 % (∆R/R) were obtained.