Innovations and Applications of Composite Hydrogels: from Polymer-Based Systems to Metal-Ion-Doped and Functional Nanomaterial-Enhanced Architectures.

Hydrogels are 3D polymer networks cross-linked by physical interactions or covalent bonds. Been considered as versatile fabrication platforms for biomaterials due to their excellent biocompatibility and water-solubility. Particularly, the single-component hydrogels exhibit similar properties as above, but have obvious restrictions such as poor mechanical properties, rapid swelling, and unexpected instability. It can limit applications in biomedicine, mechanical proceeding, and electrochemical engineering. To address these limitations, researchers have investigated composite hydrogels' construction, properties, and expanded applications. It mainly focuses on the fabrication of composite hydrogels with integrations of different materials, expanded mechanical properties, varied performances, functionalities, and obvious advantages. This review expounds on the developments in hydrogel-based polymer materials, especially the progress made in the preparation methods, the mechanism of action, and technology development. The review also explores the positive impact of the introduction of innovative elements such as metal ions, nanomaterials, and bioactive molecules on the performance of hydrogels and their pioneering works, providing new perspectives for the design and optimization of hydrogels under specific application requirements. Finally, it looks forward to the challenges and future development potential of composite hydrogels, emphasizing the continuous improvement in design, functional integration, and application suitability, and reveals further prospects in this field.