Natural biomass hydrogels for intelligent sensing: From component crosslinking engineering to stimuli-responsive mechanisms

Natural biomass hydrogels are ideal candidate materials for sensors due to the structural tunability and abundant functional groups of natural biomass, and they have been widely applied in medical diagnosis, environmental monitoring, and intelligent systems, among other areas. However, the literature lacks a comprehensive review of the inherent connection between the crosslinking network structures of natural biomass hydrogels and the sensing performance of assembled sensors. Herein, this review analyzes the molecular structure characteristics of representative natural biomass materials (such as cellulose, chitosan, sodium alginate, etc.), as well as their advantages for fabricating hydrogels and their application in sensors, including stress–strain sensors, biosensors, temperature sensors, and humidity sensors. We provide a detailed overview of the crosslinking mechanisms (such as physical crosslinking, chemical crosslinking, and dual crosslinking), crosslinking strategies, and application scope of various natural biomass hydrogels in sensors. This is followed by a summary of the sensing mechanisms in sensors assembled with natural biomass hydrogels and the impact of different crosslinking networks on the performance of various sensors. Finally, we outline the challenges and prospects for the development of sensors based on natural biomass hydrogels, from the coordinated development of crosslinking networks and dynamic response mechanisms to scalable preparation technology.