Micro-Pillar Arrays Coated with TiO2 Nanotubes on Titanium Surface for Antibacterial Activity and Enhanced Bioactivity

Titanium and its alloys are widely used for orthopedic and dental implants because of their favorable bone-matching elastic modulus, corrosion resistance, and biocompatibility. However, implant-associated infection and insufficient early osseointegration continue to compromise their long-term clinical performance. Here, inspired by natural micro- and nano-topography such as cicada wings and lotus leaves, we fabricated hierarchical surfaces comprising titanium micro-pillar arrays coated with TiO2 nanotubes. Micro-pillar arrays with scanning pitches of 40, 60, and 80 μm were fabricated via femtosecond laser ablation, followed by in situ anodization to grow TiO2 nanotubes approximately 100 nm in diameter. The hierarchical architecture integrates micro-pillars and TiO2 nanotubes to enhance antibacterial performance and bioactivity: the micro-pillar arrays coated with nanotubes provide a three-dimensional microenvironment for cell adhesion, and the TiO2 nanotubes show contact-killing antibacterial function. The 40-MNTs sample (40 μm micro-pillars coated with TiO2 nanotubes) achieved the highest antibacterial efficiency while effectively supporting mesenchymal stem cell adhesion and proliferation. These findings show that combining micro-scale geometry with nano-topographical cues can improve antibacterial performance while maintaining cytocompatibility, providing a drug-free surface engineering strategy for titanium implants.