Recyclable, Conductive Alginate-Based Hydrogels with High Stretchability and Low Electrical Hysteresis for Wireless Wearable Sensors

Abstract

Soft electronics based on conductive hydrogels hold considerable promise for advanced wearable technologies. However, these systems face critical challenges, particularly in mitigating electronic waste and ensuring electrical stability. In this study, we present a highly stretchable and recyclable hydrogel composed of the natural polymer alginate (ALG) as the matrix and the lab-synthesized poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a conductive filler, ionically crosslinked using CaCl2. The ALG/PEDOT:PSS hydrogel exhibited a stretchability of 138% and a low hysteresis of 6.65% while maintaining stable electrochemical properties over 400 stretching cycles achieved without relying on a synthetic polymer matrix. The integration of ALG with the conductive PEDOT:PSS created conductive pathways and strengthened the intermolecular interactions, resulting in a modest 1.6-fold increase in resistance under 100% strain. Skin-adaptable sensors fabricated from this hydrogel effectively detected large human movements and small activities in real-time. The sensors demonstrated notable electrical responsiveness (65.01 kΩ), good sensitivity (GF: 0.58), rapid response (0.59 s), and recovery times (0.57 s), even after recycling. Furthermore, the integration of the hydrogel into wireless sensor systems afforded a consistent and reliable performance for real-time movement monitoring. These findings highlight the potential of the fabricated hydrogel for high-performance, stretchable electronic devices, particularly due to its excellent recyclability.