Crosslinking strategy and promotion role of cellulose as a composite hydrogel component for three-dimensional printing – A review

Over the past decades, various types of hydrogels have been developed and used in the food sector to solve real-life problems. Three-dimensional (3D) printing technology can customize special surface morphologies, overall shapes, and other functionalized structures for hydrogels. Green and economical 3D printed cellulose hydrogels are rapidly attracting the research interest of researchers, especially in the field of food, where 3D printed cellulose hydrogels have a great potential for uses such as food printing or food preservation packaging. This paper summarizes and analyzes for the first time the crosslinking principle and enhancement mechanism assumed by cellulose in the research related to 3D printing cellulose hydrogels. The multi-hydroxyl character of cellulose makes it have great modification potential, which can participate in all kinds of physical or chemical crosslinking reactions, and its own elongated shape also helps it to be intertwined with other components. At the same time, cellulose promotes diverse effects on 3D printing hydrogel matrix, which not only improves the mechanical properties, shear-thinning properties, and swelling properties of the matrix, but also confers anisotropic characteristics to the hydrogel matrix, or can be used as a stabilizing support for expensive and rare materials by taking advantage of cellulose's inexpensive nature. This review provides a reference for future research on the 3D printing and molding of cellulose hydrogels and their use in the food field, and it is hoped that more and more researchers will pay attention to the abundant cellulose resources.