Rapid Synthesis of Multifunctional Hydroxyapatite Using Laser-Induced Hydrothermal Process

Synthetic biomaterials are used to overcome the limited quantity of human-derived biomaterials and to impart additional biofunctionality. Although numerous synthetic processes have been developed using various phases and methods, Existing synthetic processes suffer from issues such as lengthy processing time, challenges in size control, and difficulties in achieving high-concentration metal ion substitution for additional functionality. In this presentation, we will present a rapid synthesis method using a laser-induced hydrothermal process. Based on the thermal interaction between the pulsed laser beam and titanium plate, which was used as a thermal reservoir, hydroxyapatite particles ranging from nanometer to micrometer scale could be synthesized in seconds. Moreover, this laser-induced hydrothermal synthesis can enable metal ion substitution into the matrix of hydroxyapatite with a controllable concentration. We calculated the theoretical maximum temperature achieved by thermal interaction at the surface of the thermal reservoir based on the validation of three simplification assumptions. Subsequent linear regression analysis showed that laser-induced hydrothermal synthesis follows an Arrhenius chemical reaction. Synthesized hydroxyapatite and Mg²⁺-, Sr²⁺-, Zn²⁺-substituted apatite powders exhibited promotion of bone cell attachment and proliferation ability due to ion release from the synthesized powders, which had a low crystallinity and relatively high solubility. This laser-induced hydrothermal synthesis is expected to be used in biomaterials, catalyst, 3D printing, and solar cell technology.