(718f) Anisotropic Chitosan Hydrogels with Multiscale Layered Structures

Many biological tissues contain both macroscopic and microscopic anisotropic architectures, which not only facilitates the living organisms with mechanical toughness but also plays an essential roles in surface lubrication, force generation, and cell proliferation, etc. Anisotropic hydrogels have been developed to mimic biological tissues by self-organizing various components into hierarchical structures in the presence of directional stimuli, such as the ice-templating, mechanical forces, magnetic or electric fields, and ion gradients. Additionally, some nanofillers with high aspect ratio can be assembled into microscopic anisotropic hydrogels by utilizing the concentration or vacuum-assisted filtration technology. However, most of those hydrogels are mechanically weak, only contain single-ordered features, and limit to thin films or small-sized samples. Complicated post-processing processes are needed to fabricated anisotropic hydrogels with multi-ordered structures, which is time-consuming and may cause poor biocompatibility of the final products. In this work, we present a simple method to construct supertough multi-ordered anisotropic hydrogels at a large scale by the self-assembly of rigid chitosan nanofibers in a chemically crosslinked gel network through a controlled drying treatment. The acquired chitosan hydrogels display highly aligned self-templatedhierarchical structures at both macro- and microscopic scales. Meanwhile, their mechanical strength was enhanced as approximately ten times as that of the original gels. Taking advantage of the drying-induced realignment of polymer chains during the process, the hierarchically layered structure in the hydrogel can be controlled with desired direction.