A sustainable approach towards printed graphene ink for wireless RFID sensing applications

Graphene-based printable inks are advanced and promising candidates for flexible printed electronic devices. To develop large-scale graphene-based highly conductive electronics based on existing printing approaches of the material, it is imperative to scale up its ink production methods and optimize the electrical properties of the printed films. Here, a sustainable approach is reported for preparing high-conductive screen-printing graphene ink by recycling cellulose solvents. The ink uses Cyrene solvent in circulation and produces highly concentrated and conductive graphene ink to conquer the limitation of graphene inks in massive industrial production brought by the high cost of the cellulose solvents. A systematic study of the sheet resistance variation with the number of cycles has been carried out. The average conductivity of the ink can exceed 3 x 10(4) S m(-1), with only a 2-h shear exfoliation process, which exhibits about the same conductivity of recent works (using toxic NMP solvent, complex centrifugation, ultrasonication, etc.) but with much more straightforward and cost-effective fabrication process. The formulation of graphene inks allows flexible metal-free far-field tag antenna to be screen-printed and integrated with an off-the-shelf sensory chip to achieve battery-free wireless UHF RFID far-field temperature sensing. The high responsiveness, accuracy, and sensitivity of the RFID sensing tag were observed with instantaneous detection of accurate and reliable wireless data transmission.