Additive manufacturing of biomorphic scaffolds for bone tissue engineering

Abstract

Bone tissue engineering has evolved owing to new opportunities of deep customisation offered by additive manufacturing technologies. Gyroid structures, which have been widely used for energy absorption or chemical catalysis, are now being employed as biomorphic structures as well to provide customer-oriented scaffolds for missing or injured bones. Unfortunately, limited data in terms of manufacturability and mechanical properties are available in the literature to support a wide application scope, because the bone to match is strongly dependent on the individual. Therefore, the study aimed at addressing this lack of knowledge, assessing the manufacturability of metal gyroids and further developing the correlation of the structural response with the designed geometry, so to allow the designer to provide the proper biomorphic structure on a case-by-case basis. Biocompatible steel was used to manufacture samples via laser powder-bed fusion; their elastic moduli and yield strengths were evaluated as a function of the orientation of the elementary cells, the symmetry and the wall thickness based on compression testing. Grounds have been given to support potential applications for tibias and vertebras.

Mechanical properties and fluid permeability of gyroid and diamond lattice structures for intervertebral devices: functional requirements and comparative analysis

“…Among the three main diamond cell orientations: [001], [011] and [111], the [001] is selected, since it displays a more constant cross-sectional area along the vertical direction, thus reducing the stress riser effect and improving the tensile fatigue resistance of the structure [54]. Although some recent works study the impact of the gyroid orientation on its stiffness and strength [55][56][57], they present conflicting results, therefore the gyroid structure orientation is kept by default, and is determined by the governing equation used for its generation (Equation ( 6)):…”

Simulation of the Mechanical Behaviour of Metal Gyroids for Bone Tissue Application

“…More specifically, the hypothesis of linear isotropic hardening was implemented. Regarding the boundary conditions (Figure 2), prescribed displacements in the quasi-static compression tests were given via a Dirichlet condition [17], namely, a fixed constraint of zero displacement was set to the upper face of the specimen, whereas a pre-set speed of 1 mm/min was set to the opposite face, thus simulating the external compressive load under a condition of displacement control, according to previous studies [5,18]. Two virtual probes, for the displacement and the instant stress at the upper surface, were defined and monitored.…”

“…a pre-set speed of 1 mm/min was set to the opposite face, thus simulating the external compressive load under a condition of displacement control, according to previous studies [5,18]. Two virtual probes, for the displacement and the instant stress at the upper surface, were defined and monitored.…”

“…Additive manufacturing, instead, and the technology of laser powder bed fusion (LPBF) of metals in particular have shown significant potential for the fabrication of complex structures, including TPMSs [4], thanks to making efficient use of raw materials and producing minimal scrap while achieving satisfactory geometrical accuracy [3,4]. Interestingly, gyroids cells are self-supporting, thus preventing the need for specific supporting structures [5], which should be removed after building. In addition, customer-oriented solutions can be pursued for missing or injured bones.…”

“…Different studies have already been published, aiming at discussing the surface morphology, the mechanical properties and the manufacturability of metal gyroids via additive manufacturing [6]. It has been pointed out that many geometrical factors are involved and affect the response under loading [5]. In this frame, the results of the quasistatic compressive behaviour as a function of wall thickness and orientation of the main cells have been widely discussed [2,6] for Materials 2021, 14, 4808 2 of 13 biomorphic gyroid scaffolds of different metal alloys.…”