A Novel Manufacturing Route for Fabrication of Topologically‐Ordered Porous Magnesium Scaffolds

Abstract

The use of porous metal foams as biomaterial scaffolds has been widely adopted; however, many of these porous structures are manufactured with pore architectures that are inherently random. This makes structural optimization for a specific purpose challenging. Scaffolds containing ordered pore architectures can be fabricated to meet design criteria, such as porosity, stiffness, and volume fraction. Mg and its alloys offer potential as a new class of degradable metallic orthopedic biomaterials. In comparison with current metallic orthopedic implant materials, Mg offers advantages such as, closer‐to‐bone stiffness and biodegradability, thereby eliminating the need for a second surgery to remove hardware. Currently there are few methods described in literature to manufacture ordered porous Mg. The aim of this study was to determine the resolution of a novel indirect solid free‐form fabrication (SFF) process for producing topologically ordered Mg (TOPM) structures. The multi‐step method involved the printing of an SFF mould, NaCl infiltration, and liquid Mg casting techniques. Using a range of characterization methods, we demonstrated that the selected structures were manufactured with a high level of accuracy. Differences in dimensions from CAD models to Mg scaffolds ranged from 2.5% to a maximum of 8.33%. Similarly, there was a maximum of 6.1% reduction in porosity in Mg scaffolds compared with initial design. Meanwhile, with surface roughness of 10.17 ± 1.75 µm, there was an average of 70% increase in surface area. This study demonstrates a simple, reliable, and safe route to manufacture TOPM scaffolds for potential application in medical device design.

Porous Titanium Implants: A Review

“…[80] Singh and co-workers presented a novel method for production of titanium foams for biomedical implants. The multi-step method involved the printing of an SFF mold, NaCl infiltration, and liquid Mg casting techniques.…”

Current Status and Recent Developments in Porous Magnesium Fabrication

“…When this is compared with the temperature of molten magnesium, there is a small probability of this reaction. A TGA-DTA research [20] performed on a mixture of Mg þ CaCO 3 , preheated above the melting point of Mg, proved that the foaming gas is CO produced in an exothermic reaction (8):…”

“…[36] Moreover, it was found that Mg alloys passivation process will be easier in the presence of F À ions. [37] Another research showed that using a supersaturated Na 2 SO 4 solution [8] could handle corrosion problems. Furthermore, resulting from such leaching only negligible concentrations of Cl À (< 0.3%) were detected.…”

“…This comprises six steps: (i) creating a 3D model with the planned architecture in a CAD program; (ii) rapid prototyping of a polymer positive template; (iii) infiltrating the template under 2 MPa with paste prepared by mixing NaCl with gelatine; (iv) burning out the template and sintering of the NaCl negative preform; (v) infiltrating the preform with liquid magnesium; and (vi) removing the NaCl. [8,29] Although the porous Mg produced exhibits only slightly higher compressive strength, the structure can be designed, controlled, and there is a possibility to develop a "valley" architecture. That makes it what is desired by the biomedical industry.…”

“…[7] The choice of production method also determines the type of resulting structure. [8] In some articles, there is a classification of structures as random or topologically ordered. Another way to categorize material is based on open and closed porosity.…”