Engineering cellulosic paper into a bending strain sensor using chemical additives: Metal salt-based treatment and ethanol-assisted processing.

The pulp and paper industry, traditionally focused on basic material production, is now expanding into innovative areas, such as advanced functional materials. Papermaking wet-end chemistry & chemical additives is a specialized field that integrates process control in wet-end paper production with the versatile use of chemical additives, which can be tailored for both wet-end and non-wet-end applications. By combining the optimization of wet-end processes with the adaptability of chemical additives-designed specifically for papermaking or adapted from other industries-this field offers immense potential for bridging traditional papermaking with emerging technologies. This study introduces a cellulosic paper-based bending strain sensor enabled by two simple chemical additives: metal salt and ethanol. The sensor is fabricated through a treatment process that engineers the fiber network, enhancing its conductive properties. By transforming the paper's porous structure into a denser network, efficient conductive pathways are established. The resulting material demonstrates features like bending strain detection, isotropic sensitivity, low hysteresis, and high-frequency responsiveness. Additionally, it can sense temperature changes between 20-60 °C and remains functional at subzero temperatures. Encapsulation with polyimide further improves its waterproof and environmental stability. The metal salt-ethanol approach offers a scalable, sustainable, and cost-effective method for producing cellulosic sensors and wearable devices, providing a robust foundation for the practical adoption of innovative sensing technologies.