When nanocellulose meets hydrogels: the exciting story of nanocellulose hydrogels taking flight

The rapid development of nanocellulose and hydrogels has contributed to the development of renewable smart material technologies in recent years. Based on the excellent renewable and biodegradable properties of nanocellulose and the advantages of hydrogels with a high water content, porosity, excellent stretchability and comparable quality to living tissue, nanocellulose hydrogels, which combine the benefits of both, have received significant attention as pioneering materials in the green chemistry revolution. Herein, we present a comprehensive and systematic classification of the nanocellulose hydrogels reported to date in terms of their design-application target relationships. By revealing the intrinsic link between the inherent advantages of nanocellulose and hydrogels, we focus on the applications of nanocellulose hydrogels in medicine, electricity, sensor, environmental governance, food and agriculture and highlight their design innovation advantages. In addition, from the perspective of fundamental issues and practical applications, we provide an in-depth analysis of the shortcomings of the current nanocellulose hydrogels based on four major aspects, including their preparation, platform, application and safety and provide corresponding constructive comments to indicate the future direction of their development. By revealing the intrinsic link between the inherent advantages of nanocellulose and hydrogels, we highlight the applications of nanocellulose hydrogels in medical treatment, electricity, sensor, environmental governance, food, and agriculture.