Hierarchical Micro/Nanostructured Anodized Surface for a 3D-Printed Bioactive Kinetic Screw

Technological development in surface treatment for biomedical implants has advanced rapidly, yet the integration of additive manufacturing with controlled nano topography remains underexplored. This study investigates a novel bioactive kinetic screw (BKS) produced by 3D printing and CNC machining, followed by different anodization treatments: plasma electrolytic oxidation (PEO), hard anodization (HA), and soft anodization for TiO2 nanotube (TNT) formation. Scanning electron microscopy revealed that PEO created a uniform macro–micro porous surface with pore sizes ranging from 5–15 µm and porosity values of 22.4 ± 3.2%, while HA produced smaller, less homogeneous pores (0.5–2 µm, porosity 10.7 ± 2.6%). TNTs were successfully formed with an average diameter of 80 ± 12 nm, although distribution was non-uniform in screw grooves. Preliminary finite element analysis demonstrated that Ti6Al4V nanotubes (diameter 50 nm, length 500 nm) withstood applied torque with maximum von Mises stress of 1.5 × 10−8 N/nm2 and maximum strain of 3.56, indicating mechanical resilience compatible with early implant loading. The findings demonstrate that the proposed anodization protocols generate distinct hierarchical surface morphologies on BKS implants while preserving implant geometry. These results provide a structural basis for future investigations of biological performance.