Bioprocess-Inspired Microscale Additive Manufacturing of Multilayered TiO2/Polymer Composites with Enamel-Like Structures and High Mechanical Properties

摘要

Natural structure-forming processes found in biological systems are fantastic and perform at ambient temperatures, in contrast with anthropogenic technologies that commonly require harsh conditions. A new research direction “bioprocess-inspired fabrication” is proposed to develop novel fabrication techniques for advanced materials. Enamel, an organic–inorganic composite biomaterial with outstanding mechanical performance and durability, is formed by repeating the basic blocks consisting of columnar hydroxyapatite or fluorapatite and an organic matrix. Inspired by the enamel formation process, a microscale additive manufacturing method is proposed for achieving a multilayered organic–inorganic columnar structure. In this approach, rutile titanium dioxide (TiO2) nanorods, polymers, and graphene oxide (GO) are sequentially assembled in a layer-by-layer fashion to form an organic–inorganic structure. In particular, GO serves as a substrate for TiO2 nanorods and interacts with polymers, jointly leading to the strength of the composites. Impressively, this enamel-like structure material has hardness (1.56 ± 0.05 GPa) and ultrahigh Young’s modulus (81.0 ± 2.7 GPa) comparable to natural enamel, and viscoelastic property (0.76 ± 0.12 GPa) superior to most solid materials. Consequently, this biomimetic synthetic approach provides an in-depth understanding for the formation process of biomaterials and also enables the exploration of a new avenue for the preparation of organic–inorganic composite materials.