Enamel-inspired composite with robust mechanical properties and self-healing capability

Echoing the regenerative powers of living organisms, self-healing materials can recover from damage, extending their lifespan and enhancing dependability, thus holding broad applications promise across diverse fields, including biological tissue engineering, soft robotics, flexible electronics, and automotive industries. Nonetheless, self-healing materials typically suffer from poor mechanical properties, a limitation stemming from the inherent trade-off between mechanical robustness and self-healing capability. Inspired by dental enamel, we report a composite featuring an aligned array of hydroxyapatite nanowires (HAP NWs) interwoven with dynamic borate bond networks by a bidirectional freeze-drying method, boasting favorable mechanical robustness and high self-healing capabilities. Benefiting from the distinct enamel-like microstructure coupled with the strong interactions between the polymer matrix and the HAP NWs, this composite can effectively transmit stress and dissipate energy to prevent crack propagation. Therefore, an impressive mechanical modulus of 4.43 ± 0.09 GPa, strength of 173.47 ± 6.36 MPa, and toughness of 2.18 ± 0.20 MPa m^1/2 are achieved while maintaining a self-healing efficiency of 97.7%. This approach paves the way for preparing materials that blend superior mechanical attributes with the intrinsic ability to self-repair.