Stimuli-Responsive nanocellulose Hydrogels: An overview

Nanocellulose, with its high aspect ratio, large specific surface area, favourable modifiability, high mechanical strength, renewability, and biodegradability, has attracted significant attention over the last decade. Nanocellulose hydrogels are composite porous materials combining nanocellulose and a polymer, and they exhibit excellent water retention and mechanical properties. Stimuli-responsive nanocellulose hydrogels are not only environment-friendly but also exhibit specific responsiveness and detection capability to environmental stimuli; therefore, they have remarkable potential applicability in biomedicine, bionic intelligent materials, and sensing detection. This review aims to examine the latest developments in stimuli-responsive nanocellulose hydrogels, including their preparation, properties, and applications. The responsive behaviours of nanocellulose hydrogels are comprehensively discussed, including the effects of temperature, pH, ionic strength, light, redox agents, and electric and magnetic fields. This review also summarises the applications of stimuli-responsive nanocellulose hydrogels in detection, biomedicine, and soft actuators. Finally, it provides insights into the challenges and opportunities in the future.