Chitin Nanocrystals as an Eco-friendly and Strong Anisotropic Adhesive.

To solve the damage to the environment and human body caused by organic solvent adhesives in the utilization process, chitin nanocrystal (ChNC) suspension is explored as a strong anisotropic adhesive, which is an eco-friendly and water-based adhesive with high adhesive strength. ChNCs extracted from crab shells are rod-like nanoparticles with high aspect ratios, which are mainly employed as reinforcing polymer nanocomposites and biomedicine nanomaterials. ChNC suspension sandwiched between substrates forms a long-range ordered superstructure by a self-assembly process. ChNC nanoglue exhibits high anisotropy adhesion strength, i.e., an in-plane shear strength (5.26 MPa) and an out-of-plane shear strength (0.46 MPa) for glass substrates. Moreover, the ChNC nanoglue is suitable to many substrates, such as glass, plastic, wood, metal, paper, etc. The ChNC nanoglue shows high biocompatibility toward the fibroblast cell and rat skin, proving their excellent biosafety. As an eco-friendly and high-performance adhesive, ChNC nanoglue shows promising applications in daily life and industrial fields.