Water-Based Graphene Inks for All-Printed Temperature and Deformation Sensors

Graphene (G) has been combined with carboxymethyl cellulose (C) for the development of environmentally friendly inks for printed electronics applications. Water-based ink formulations have been developed for screen-printing with graphene content up to 90 wt %. The printed patterns show a good distribution of the graphene within the cellulose matrix, allowing a good screen-printed pattern definition with a line thickness of 200 μm. The electrical percolation threshold is found to be around 0.18 of volume fraction, corresponding to 1.9 wt % of graphene in the ink composition. A maximum electrical resistivity of ρ = 1.8 × 10–2 Ω m has been obtained for the G90:C10 ink composition, allowing the printing of suitable conductive patters for printed electronics. Further, the multifunctionality of the developed inks is demonstrated by the interesting thermoresistive and piezoresistive properties of the screen-printed G30:C70 and G65:C35 materials, respectively. The maximum thermoresistive sensitivity of S = −0.27 and piezoresistive Gauge factor (GF) of 1 < GF < 5 demonstrate the suitability of the materials for temperature and deformation sensors, respectively, demonstrating the multifunctionality of the materials and their wide range of potential applications in the area of printed electronics.