Ultralong Hydroxyapatite Nanowires: Promising Flexible Building Blocks for Constructing High-Performance Biomimetic...

Traditional hydroxyapatite materials are inherently stiff and brittle, limiting their applications. Flexible ultralong hydroxyapatite nanowires, characterized by nano-scale diameters and micrometer-scale lengths, offer a promising alternative as one-dimensional flexible building blocks for constructing high-performance biomimetic materials. Nature has evolved a variety of high-performance materials with hierarchically ordered structures assembled from nano-scale building blocks, which provide valuable insights into the design and ordered assembly of flexible nanofibers for building high-performance biomimetic materials. Currently, how to distill the structural design principles of natural materials to engineer flexible nanofibers into advanced high-performance biomimetic materials with excellent properties and multifunctions remains a frontier scientific challenge. In 2014, the authors' research group reported for the first time the calcium oleate precursor solvothermal method for the synthesis of flexible ultralong hydroxyapatite nanowires and their applications. Since then, many soft functional materials and high-performance biomimetic materials have been designed and prepared using flexible ultralong hydroxyapatite nanowires, and their applications in various fields have been explored. These studies demonstrate the successful assembly of flexible ultralong hydroxyapatite nanowires into hierarchical biomimetic structures inspired by natural materials such as enamel, nacre, and bone, which exhibit enhanced mechanical properties, including improved strength, toughness, and flexibility, alongside multifunctional capabilities like thermal insulation and biomedical compatibility. These findings suggest that flexible ultralong hydroxyapatite nanowires provide a versatile platform for designing and constructing advanced biomimetic materials with promising applications in various fields. This review article aims to briefly review recent advances in this exciting and rapidly evolving research field. The synthetic methods, assembly strategies, properties, and applications of flexible ultralong hydroxyapatite nanowires and their derivative biomimetic materials are discussed, enlightening their structural design principles and potential applications. Finally, we propose future research directions and future perspectives in this exciting frontier research field.