Magnetically oriented chitin/C-Fe-MOF composite hydrogel with high toughness and conductivity for advanced soft...

Hydrogels have gained increasing attention as flexible and conductive materials for soft electronics manufacturing. However, integrating skin-like multifunctionality into a gel that can be used under various conditions remains a significant challenge. Herein, we proposed a novel "one-stone-two-birds" strategy by utilizing carbonized iron-based metal-organic framework (C-Fe-MOF) microparticles as functional fillers to simultaneously enhance mechanical strength and electrical conductivity of a chitin-based composite hydrogel (CEF). The C-Fe-MOF fillers in the CEF hydrogel were magnetically aligned along the direction of external magnetic field, forming a well-ordered three-dimensional conductive network. C-Fe-MOF microparticles significantly reduced interparticle spacing, forming continuous electron conduction pathways. The magnetic field-induced alignment process disrupted the original crystalline domains of chitin enhancing the amorphous nature of the matrix. This loosely amorphous structure provided smoother pathways for ion migration, enabling synergistic conduction of electrons and ions. This oriented structure not only increased the tensile strength at -20 °C by 2.5 times compared to the original chitin hydrogel, but also raised the conductivity to 0.324 S/m, which was 4.3 times higher than that of pure chitin hydrogel. Systematic characterization revealed that the C₃E₄F₂ hydrogel displayed optimal mechanical strength and electrical conductivity, with its rapid response time (42 ms). This work establishes a novel approach for functionally modifying natural polymer-based hydrogels via magnetic field-guided structural design, offering a theoretical foundation for the practical use of CEF hydrogels in next-generation flexible electronic devices.