Ionically conductive and stretchable cellulose/tannic acid films as a platform for multifunctional wearable electronics

Abstract

Stretchable and conformable on-skin sensors have emerged as a key technology for real-time physiological monitoring, interactive human-machine systems, and soft robotics applications. However, conventional sensors are often based on synthetic polymers with poor biodegradability and limited biocompatibility, raising concerns about environmental sustainability and long-term skin contact. In this study, we report a multifunctional, biodegradable, and stretchable sensing platform based on a NaCl-treated carboxymethyl cellulose (CMC)/tannic acid (TA) hybrid film to overcome these limitations. We present a unique combination of material simplicity, biocompatibility, and multifunctional performance. The resulting films exhibit excellent stretchability (up to 300%), with optimized mechanical properties (Young’s modulus of 0.287 MPa, Toughness of 0.584 MJ/m3), and conformal skin adhesion without residue. Electrical characterization showed reliable strain sensitivity (GF = 1.1), fast response/recovery times (~ 0.33 s), and high ionic conductivity (1.44 S/m). The films enable multimodal sensing by accurately detecting human motion, temperature changes with a temperature coefficient of resistance of − 3.31%/°C, and variations in humidity. In addition, they provide effective ultraviolet shielding while maintaining high transparency in the visible spectrum. These combined properties highlight the CMC/TA/NaCl film as an eco-friendly and high-performance material platform suitable for next-generation wearable electronics.