Soft, Sustainable, and Sensitive: Biopolymer-Based Hydrogels as Recyclable Temperature Sensors for Skin-Integrated Electronics

The development of sustainable, soft, and recyclable materials for skin-integrated electronics is critical for advancing wearable health monitoring while minimizing electronic waste. Here, chitosan-agarose-based hydrogels integrated with poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) are fabricated as recyclable, biocompatible, and thermoresponsive materials for flexible temperature sensors. The hydrogels are synthesized using a green and easy process, forming interpenetrated dual networks that exhibit high water content, mechanical compliance, and enhanced electroconductivity. Morphological analysis reveals highly porous interconnected structures, while Fourier transform infrared spectroscopy confirms the successful incorporation of PEDOT:PSS. The hydrogels display high swelling capacity, tunable mechanical properties within the physiological range of human skin, and enhanced electrochemical performance. The temperature-sensing capability of the hydrogels demonstrates a negative temperature coefficient of resistance (TCR) of up to -1.5% °C^-1, outperforming similar hydrogel-based sensors while maintaining stability over repeated thermal cycles. Importantly, the hydrogels can be disassembled, reprocessed, and reused for multiple sensing cycles without significant loss of performance, demonstrating true recyclability and supporting circular material use in soft electronics. The convergence of natural biopolymers with conducting polymers within these hydrogels provides a promising platform for developing eco-friendly, flexible bioelectronic devices, aligning with the requirements of sustainable materials science while addressing the need for high-performance, soft temperature sensors for wearable healthcare applications.