In-situ Damascus-patterning enables tunable surface electric fields for bioactive titanium implants

Conventional titanium implants, although biocompatible, are inherently bioinert and typically require complex surface modifications to achieve satisfactory osseointegration. Here, we report a new additive manufacturing strategy that directly imparts bioactivity to high-performance titanium-tantalum implants (elastic modulus: 60-80 GPa; strength: >1100 MPa) through in situ compositional modulation, and this functionality is retained after subsequent subtractive processing. By precisely regulating the extent to which tantalum melts into the titanium matrix during laser powder bed fusion, periodic Damascus-like compositional patterns are generated that, after simple oxidation, produce stable periodic surface potential differences (P-SPD) tunable from 5.59 to 48.01 mV, spanning the range observed in natural tissues. The resulting electric field (∼2.35 V/m) also lies within the biologically active range used in external stimulation studies to promote osteogenesis, directed migration, and neural responses. The resulting endogenous electric field nearly doubles osteogenic performance relative to Ti64ELI controls, as evidenced by both in vitro assays and in vivo cranial defect repair. Mechanistic studies further reveal that P-SPD promotes both cell migration and osteogenic differentiation. This work establishes a strategy for the in situ integration of structural and biological functions through controlled melting behavior, offering a new paradigm for the surface functionalization of bioimplants.