Two-birds-one-stone strategy for synergistically enhanced electromechanical properties of double network hydrogels

Conductive polymer-based double network (DN) hydrogel sensors represent a key development direction for future flexible electronics, primarily due to their enhanced adaptability and stability in wearable applications. Unfortunately, existing conductive polymer-based DN hydrogel systems often face a trade-off between mechanical and electrical properties, frequently compromised by the introduction of non-conductive templates and hydrophobic aggregation. This challenge, however, can potentially be addressed by the introduction of functionalized carbon materials, which are expected to improve the mechanical properties of double network hydrogels. Simultaneously, the π-π interaction between graphitic carbon and the conductive polymer offers a route to enhance the conductivity of DN hydrogels. Here, we propose a two-birds-one-stone strategy to construct a conductive polymer-based DN hydrogel, explicitly aiming for the synergistic enhancement of both mechanical and electrical properties. As a proof of concept, carboxylated Zeolitic Imidazolate Framework-8 derived carbon (C-ZIFC) was introduced into a polyvinyl alcohol/ polyaniline (PVA/PANI) DN hydrogel to achieve improved electromechanical performance. To counteract the phase separation defects caused by carbon particles, small molecular cross-linkers were employed to effectively "sew" them together, resulting in a hydrogel network with a dense cross-linked structure. The resulting hydrogel demonstrated high strain (550%), excellent stress (0.41 MPa), and good conductivity (5.81 S/m). We successfully integrated the hydrogel into a flexible strain sensor for applications such as human joint monitoring and Morse code information transmission. This work not only provides new design ideas for high-performance wearable electronics based on hydrogel sensors but also significantly expands their application scope.