Additive manufacturing of multi-morphology graded titanium scaffolds for bone implant applications

Porous Titanium scaffolds have attracted widespread attention as bone implants for avoiding the stress shielding effect and promoting bone-in-growth.In this study,multi-morphology graded scaffolds hy-bridized by Primitive and Gyroid structures with porosity of 50,60,and 70%were designed(denoted as PG50,PG60,and PG70,respectively)and fabricated by selective laser melting.The simulation results showed that the maximum von-Mises stress of hybridized scaffolds increased from 504.22 to 884.24 MPa with porosity.The permeability and average pore size of multi-morphology PG50,PG60,and PG70 were in the range of 3.58×10^(-9)-5.50×10^(-9) m^(2) and 568.1-758.4μm,respectively.The microstructure of multi-morphology graded scaffolds consisted of a fully martensiticα′phase.Tested permeabilities of PG50 and PG60 were 3.27×10^(-9) and 4.35×10^(-9) m^(2),respectively,which were within the range of human bone(0.01-12.1×10^(-9) m^(2)).Elastic modulus and compressive yield strength of PG50 and PG60 ranged within 5.93^(-9).86 and 180.06-257.08 MPa,respectively.Therein,the PG50 not only exhibited a similar elastic modulus compared to human cortical bone(10.1 GPa)but also had higher strength(257.08 vs 131 MPa).The results of in vitro biocompatibility assay showed that PG50 and PG60 have better cyto-compatibility than mono-morphology scaffolds with the same porosity.Taken together,PG50 is promising to be used for the restoration of bone defects due to its excellent mechanical properties,appropriate per-meability,and good cytocompatibility.

Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti(CP-Ti)

Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration due to their superior structural,mechanical,and biological properties.In this study,six types of composite lattice structures with different strut radius that consist of simple cubic(structure A),body-centered cubic(structure B),and edge-centered cubic(structure C)unit cells are designed.The designed structures are firstly simulated and analysed by the finite element(FE)method.Commercially pure Ti(CP-Ti)lattice structures with optimized unit cells and strut radius are then fabricated by selective laser melting(SLM),and the dimensions,microtopography,and mechanical properties are characterised.The results show that among the six types of composite lattice structures,combined BA,CA,and CB structures exhibit smaller maximum von-Mises stress,indicating that these structures have higher strength.Based on the fitting curves of stress/specific surface area versus strut radius,the optimized strut radius of BA,CA,and CB structures is 0.28,0.23,and 0.30 mm respectively.Their corresponding compressive yield strength and compressive modulus are 42.28,30.11,and 176.96 MPa,and 4.13,2.16,and 7.84 GPa,respectively.The CP-Ti with CB unit structure presents a similar strength and compressive modulus to the cortical bone,which makes it a potential candidate for subchondral bone restorations.

Characteristics of novel Ti-10Mo-xCu alloy by powder metallurgy for potential biomedical implant applications

When biomaterials are implanted in the human body,the surfaces of the implants become favorable sites for microbial adhesion and biofilm formation,causing peri-implant infection which frequently results in the failure of prosthetics and revision surgery.Ti-Mo alloy is one of the commonly used implant materials for load-bearing bone replacement,and the prevention of infection of Ti-Mo implants is therefore crucial.In this study,bacterial inhibitory copper(Cu)was added to Ti-Mo matrix to develop a novel Ti-Mo-Cu alloy with bacterial inhibitory property.The effects of Cu content on microstructure,tensile properties,cytocompatibility,and bacterial inhibitory ability of Ti-Mo-Cu alloy were systematically investigated.Results revealed that Ti-10Mo-1Cu alloy consisted ofαandβphases,while there were a few Ti2Cu intermetallic compounds existed for Ti-10Mo-3Cu and Ti-10Mo-5Cu alloys,in addition toαandβphases.The tensile strength of Ti-10Mo-xCu alloy increased with Cu content while elongation decreased.Ti-10Mo-3Cu alloy exhibited an optimal tensile strength of 1098.1 MPa and elongation of 5.2%.Cytocompatibility study indicated that none of the Ti-10Mo-xCu alloys had a negative effect on MC3T3-E1 cell proliferation.Bacterial inhibitory rates against S.aureus and E.coli increased with the increase in Cu content of Ti-10Mo-xCu alloy,within the ranges of 20-60%and 15-50%,respectively.Taken together,this study suggests that Ti-10Mo-3Cu alloy with high strength,acceptable elongation,excellent cytocompatibility,and the bacterial inhibitory property is a promising candidate for biomedical implant applications.