Liquid‐Phase Engineering of Nanocellulose Gels for Enhanced Mechanical Performance and Multifunctionality

Nanocellulose composite gels have emerged as promising materials owing to their high mechanical strength and biocompatibility, enabling applications in flexible electronics, biomedical devices, and energy storage systems. Nevertheless, conventional designs relying solely on polymer‐nanocellulose networks often fail to achieve all desirable properties. Recent studies demonstrate that incorporating a rationally selected liquid phase, including organic solvents to ionic liquids, and deep eutectic solvents, can significantly improve the mechanical robustness, environmental stability, and multifunctionality of nanocellulose gels. This review summarizes recent advances in the structural design and functional enhancement of nanocellulose composite gels, with a particular focus on liquid‐phase engineering. First, we introduce the structures and types of nanocellulose and their properties relevant to gel formation. Second, fabrication strategies for pure nanocellulose gels and nanocellulose composite gels are described, focusing on physical and chemical interactions that determine network stability. Third, this review highlights how tailored liquid phases generate hydrogels, organohydrogels, ionogels, and eutectogels with distinct properties. Fourth, the review summarizes advanced functional properties enabled by liquid‐phase engineering, including self‐adhesion, high ionic conductivity, self‐healing capability, and environmental adaptability. Finally, we discuss the remaining challenges and future opportunities, providing perspectives on the rational design of next‐generation high‐performance nanocellulose gel materials.