Graphene Oxide/Cuo-Coated Traditional Hanji Cellulose Paper for Wearable Thermal Heaters

The demand for lightweight, flexible, and energy-efficient thermal heaters is growing for applications in wearable technology, thermal management, and smart electronics. However, achieving stable and uniform heating performance under mechanical deformation remains a critical challenge for conventional flexible heaters. In this study, we developed an advanced Hanji-based thermal heater by integrating graphene oxide (GO) and copper oxide (CuO) coatings to enhance electrical conductivity and Joule heating efficiency. The synergistic interaction between GO and CuO facilitated superior charge transport and robust conductive networks, resulting in rapid and efficient electrothermal performance. The optimized GO/(10%)CuO-coated Hanji exhibited a low sheet resistance of 6.3 kΩ/sq and achieved a surface temperature of ~ 80 °C within 180 s under low voltage operation. Unlike conventional polymer-based flexible heaters, the Hanji-based heater maintained stable and uniform heating even under various bending conditions, demonstrating exceptional mechanical flexibility, durability, and reliability. Furthermore, its multifunctional capabilities were validated through effective deicing performance and wearable sensing applications, distinguishing it from commercial and state-of-the-art thermal heaters. These results establish GO/CuO-coated Hanji as a sustainable, high-performance material for next-generation flexible thermal management systems and multifunctional smart devices.