Effect of designed pore size on properties of additively manufactured TC4 with micro-nano biomedical surface

Superior mechanical properties and biocompatibility of TC4 alloy, combined with the precision of selective laser melting (SLM), make it a promising candidate for biomedical applications. In this study, TC4 specimens featuring microporous architectures with pore sizes of 300, 500, and 700 μm were fabricated via SLM. A micro-nano composite surface was further engineered through anodization. This work systematically investigated the influence of anodization voltage on nanotube diameter, as well as the effect of anodization duration on tube length, along with the evolution of nanotube morphology and array uniformity under varying processing parameters. At lower voltages, the nanotube arrays exhibited disorder and innertube adhesion. As the voltage increased from 20V to 40V, the nanotube diameter expanded from 50 nm to 106 nm; however, excessively high voltages reduced the nanotube growth rate. Furthermore, appropriate acid etching and ultrasonic cleaning process prior to anodization enhanced the quality of the nanotube arrays, which is beneficial for cellular ingrowth within the pores. Additionally, this study systematically evaluated the regulatory effect of pore size on the corrosion resistance and biomedical performance of the samples. It was observed that larger pores correspond to a reduction in corrosion resistance. And in vitro cellular experiments further revealed that cell distribution and differentiation within 300 μm pores were less favorable compared to the other groups, whereas the 700 μm porous structures exhibited the most pronounced capacity to promote cell growth, making them an optimal porous architecture for SLM-fabricated orthopedic implants.