3D-printed multiphasic biocomposite architectures for load-bearing medical implants

• Multi-phase 3D printing successfully fabricated hybrid resin-titanium alloy (Ti6Al4V) biomedical implants. • Hierarchical surface engineering on titanium alloy, utilizing Al 2 O 3 atomic layer deposition, enhanced interfacial bonding strength with resin. • 3D-printed medical scaffolds exhibited improved mechanical properties, including stiffness, strength, and energy absorption. • Innovative, lightweight, and high-strength patient-specific partial mandible implants were developed for effective large-scale load-bearing bone defect reconstruction. Conventional bone implant materials are limited in achieving high mechanical strength and lightweight design at the same time. To achieve this balance, this study introduces a multi-material design strategy for lightweight, load-bearing structures that incorporates engineered titanium-alloy plates within a bioactive 3D-printable resin composite. The resin is composed of urethane dimethacrylate and triethylene glycol dimethacrylate, enriched with bioactive nano-hydroxyapatite, and strontium-doped SiO 2 glass particles. Titanium-alloy plates underwent surface treatments, including sandblasting, chemical etching, and Al 2 O 3 atomic layer deposition, establishing a hierarchical interfacial structure. Multi-material additive manufacturing allowed for the precise embedding of titanium plates within the polymer composite matrix. The interfacial shear strength significantly improved from 4.98 MPa for untreated interfaces to 16.60 MPa after treatment, shifting the failure mode from adhesive to cohesive fracture. Additionally, the compressive modulus of the three-layer structure increased from 2.54 ± 0.10 GPa to 2.79 ± 0.03 GPa. When demonstrated with a segmental mandibular implant prototype, the design exhibited enhanced stiffness and energy absorption, with compressive energy absorption rising from 6.88 ± 0.35 J to 7.72 ± 0.47 J, and a transition from catastrophic to progressive failure behavior. This framework effectively integrates surface treatment, interfacial morphology, and mechanical performance for advanced multiphasic additive manufacturing.