A strong and tough hydroxyapatite-based fiber with enamel-inspired hierarchical structure

The hierarchical structure of tooth enamel can inspire the preparation of high strength and high toughness biomimetic composites, but fully mimicking the entire hierarchy of tooth enamel is still challenging. Here, we show that synthetic hydroxyapatite (HAP) microbundles containing a long range of ordered crystalline/amorphous HAP nanowires can be spun into enamel-inspired high-performance macroscopic fiber through shear-induced assembly. The highly ordered nanowire-microbundle structure as well as the strong interfacial connection between HAP nanowires, HAP microbundles, and the polymer matrix, leads to a hierarchical energy dissipation route, which enables this enamel-inspired fiber with a high strength and toughness of 196.3 MPa and 46.3 MJ m⁻³, exceeding the fracture toughness of previously reported HAP-based hybrid fibers. This hierarchical enamel-inspired design strategy provides a new sight into the development of high strength and high toughness fibers for potential engineering and bio-repair applications.