Acid-Induced In Situ Phase Separation and Percolation for Constructing Bi-Continuous Phase Hydrogel Electrodes with High Conductivity and Robust Mechanical Properties

Abstract Conductive polymer hydrogels have emerged as promising materials for wearable bioelectronics due to their inherent biocompatibility and stability in physiological conditions. However, achieving hydrogel electrodes with excellent conductivity and mechanical properties is challenging due to the inherent contradiction between the hydrophobicity of conductive materials and the hydrophilicity of hydrogels. Herein, we introduce a hydrogel integrating PVA, PVP and PEDOT:PSS, and propose a single-step acid-induced strategy that not only facilitates gelation but also ensures in situ phase separation of PEDOT:PSS under mild conditions, resulting in a unique bi-continuous phase structure combining excellent electrical and mechanical properties. Upon reaching the percolation threshold at 4.8 mg mL-1 PEDOT:PSS, the electrical conductivity surges to 906 mS cm-1. The hydrogel also exhibits unprecedented mechanical resilience, with a fracture strain of 1103%, significantly surpassing previous reports of PEDOT:PSS-based conductive materials. This stretchability, coupled with low mechanical hysteresis (dissipation energy less than 1.2 kJ m-3) and a resilience rate of approximately 95%, highlights its superior mechanical integrity and fatigue resistance. The hydrogel electrodes demonstrate substantially lower noise power (4.9 μV²) compared to commercial gel electrodes (1541.8 μV²) and Ag/AgCl electrodes (>34.4 μV²). The hydrogel sets a new benchmark for the performance of conductive hydrogels in wearable bioelectronics, offering exceptional mechanical properties and superior electrical functionality for efficient and reliable monitoring of biological signals.