Nonlinear continuous gradient-regulated porous architectures fabricated by selective laser melting for enhanced biomechanical compatibility

While notable progress has been made in the design and fabrication of titanium alloy biomimetic bone prostheses, existing prostheses struggle to achieve personalized matching of mechanical characteristics with patients' bone tissue due to the constraints imposed by individual differences in patients' bone quality. This leads to poor postoperative prognosis for patients, with a high likelihood of stress shielding and bone resorption. Designing a continuously nonlinear gradient bionic bone with the elastic modulus of the bone to be repaired as the target parameter can effectively improve the deformation coordination between the implanted prosthesis and the native bone under biomechanical action. In this study, selective laser melting technology was used to fabricate three types of porous structures that match the gradient transition between cortical bone and cancellous bone, namely Diamond, Gyroid, and Schoen I-graph-wrapped package (IWP) structures. Controllable, nonlinear, and continuous gradient Triply Periodic Minimal Surface porous structures with micrometer-level precision were successfully fabricated via the selective laser melting process. The results indicate that the equivalent elastic modulus of porous structure of titanium alloy lies within the physiological range for human bones. Compared to models with homogeneous porosity, the gradient design lowers the modulus parallel to the gradient direction, while maintaining reasonable compressive strength and ductility perpendicular to the gradient. Furthermore, the curvature of the gradient function exhibits a significant regulatory effect on the mechanical properties of all three distinct types of lattices. This research expands the adjustable dimensions and adjustment space for the design of personalized bionic bones and provides references and a theoretical basis for the conduct of subsequent related studies.