Biomimetic superelastic sodium alginate-based sponges with porous sandwich-like architectures.

Design and fabrication of structurally optimized three-dimensional porous materials are highly desirable for engineering applications. Herein, through a facile bidirectional freezing technique, we prepared superelastic biomass sponges in air and underwater, which possess biomimetic porous sandwich-like architectures with lamellar layers interconnected by porous microstructures, similar to the structure of rice stems. This distinctive architecture was obtained by incorporating Typha orientalis fibers (TOFs) and graphene oxide (GO) nanosheets into sodium alginate (SA) matrix, in which SA flakes and GO nanosheets were intimately grown along TOFs. The porous sandwich-like microstructure allows stress to be distributed throughout the lamellar to avoid stress concentration and endows SA/TOFs/GO sponge with excellent mechanical compressibility and recoverability. Especially, underwater superelasticity and superoleophobicity of the sponge facilitates removal of water-miscible contaminants or oil/water separation with high efficiency. This novel strategy for the design biomimetic architecture of superelastic biomass sponge can promote its application for protecting environment.