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Materials Science in Additive Manufacturing Preparation and modification of porous Ti

matching degree of its mechanical properties with human Reagent type, concentration, and etching time affect the
tissues, cannot change the fact that titanium alloy is a material’s surface properties. In addition, the composition
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bioinert metal. Several problems such as inflammation and structure of porous titanium alloys also affect the
and bone resorption in the human body still persist with material’s surface roughness and mechanical properties.
using this kind of alloy. In addition, porous implants also Civantos et al. chemically etched porous titanium
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face problems such as antimicrobial/inducible/osteogenic/ scaffolds for manufacturing additives by hydrofluoric acid
wear/corrosion resistance. Therefore, in addition impregnation and studied the effect of etching time (125
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improving mechanical properties (strength and modulus) s, 625 s) on the biological properties. The results showed
through material development and structural design, that 125 s of porous titanium etching time was more
augmenting the performance of porous implants through conducive to cell adhesion, while 625 s of etching promoted
surface modification has become the focus of researchers. 90 cell osteoblastic differentiation. However, etching will
Porous implants have a complex internal structure, and also hurt the mechanical properties of porous titanium.
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it is difficult to penetrate the interior of the implants by Wang et al. investigated the effect of etching time on the
means of the strong plastic surface processing techniques, mechanical properties of porous titanium in a hydrochloric
such as friction stir, shot peening , and femtosecond acid solution containing 20% (mass fraction). Pitting and
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laser. Therefore, the modification of porous implants grain boundary corrosion occurred in a hydrochloric acid
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mostly takes fluid (gas and liquid) as the medium, by solution on porous titanium’s inner and outer surfaces. With
modifying the surface morphology of porous titanium or time, the number and size (diameter and depth) of etching
adding components, as shown in Figure 9. In this section, pits increased significantly, and the material strength
based on the working principle of surface modification, decreased from 152 MPa to 106 MPa after 150 min.
the medical porous titanium alloy is divided into four Etching plays an important role in the early surface
categories: physical modification, chemical modification, modification of porous implants due to its simplicity and
biological modification, and composite modification low cost of operation. However, it is difficult to control
(or compound method), and the advantages and the surface morphology of the material, and the corrosion
disadvantages of different methods and influencing factors process can cause cracks or stress concentration, which
are summarized. affects the fatigue performance of the scaffold.
4.1. Physical modification 4.2. Chemical modification
The physical method mainly refers to the modification of The chemical method is used to introduce inorganic
the surface structure and roughness of porous titanium. materials or organic components onto the surface of
The surface roughness and surface free energy of materials porous scaffold, contact them with cells/tissues, or release
are the necessary conditions that affect cellular processes functional components, and then affect cell behavior
such as protein adsorption, cell adhesion, migration, and to achieve bone formation or an antibacterial effect.
differentiation. The use of chemical reagents and strong According to the processing methods, it is mainly divided
acids to etch titanium alloys is a common method to into chemical molecular dipping, vapor deposition, and
change the surface structure of materials. 94 electrochemical methods.

Figure 9. Schematic diagram of morphologic modification of porous implants or surface modification by adding components in a liquid environment.

Volume 3 Issue 1 (2024) 12 https://doi.org/10.36922/msam.2753