Inkjet-Printed Temperature Sensor From Eco-Friendly Edge-Oxidized Graphene Oxide Ink on Biodegradable Polyvinyl Alcohol Substrate

Deviations from the body's established temperature norms have functioned as vital markers for detecting illness. Developing flexible and printed temperature sensors using green materials is an effective solution for real-time wearable health-care monitoring. In this study, an environmentally conscious approach was taken to fabricate a temperature-sensitive electrode by formulating an eco-friendly ink comprising alkali-lignin-assisted edge-oxidized graphene oxide. This ink is then meticulously printed onto a biodegradable polyvinyl alcohol substrate, enabling precise deposition of the temperature-sensitive material using the inkjet printing technique. By leveraging the exceptional properties of graphene and its derivatives, particularly their sensitivity to temperature changes, the resulting electrode demonstrates promising capabilities in detecting variations in temperature. The printed temperature sensor electrode showed a linear decrease in the resistance with changes in the temperature. The decrease in the resistance is related to the thermal generation of charge carriers and phonon–electron scattering at edges and defects in the graphene oxide structure. The printed electrode also showed good stability with step change in the temperature demonstrating signal stability and reproducibility. The sensor also demonstrated a remarkable thermal coefficient of resistance of 0.14% °C⁻¹ for the temperature range of 25–42 °C, indicating good sensitivity, recovery, and drift response.