Mechanical performance of highly permeable laser melted Ti6Al4V bone scaffolds

Abstract

Critically engineered stiffness and strength of a scaffold are crucial for managing maladapted stress concentration and reducing stress shielding. At the same time, suitable porosity and permeability are key to facilitate biological activities associated with bone growth and nutrient delivery. A systematic balance of all these parameters are required for the development of an effective bone scaffold. Traditionally, the approach has been to study each of these parameters in isolation without considering their interdependence to achieve specific properties at a certain porosity. The purpose of this study is to undertake a holistic investigation considering the stiffness, strength, permeability, and stress concentration of six scaffold architectures featuring a 68.46-90.98% porosity. With an initial target of a tibial host segment, the permeability was characterised using Computational Fluid Dynamics (CFD) in conjunction with Darcy's law. Following this, Ashby's criterion, experimental tests, and Finite Element Method (FEM) were employed to study the mechanical behaviour and their interdependencies under uniaxial compression. The FE model was validated and further extended to study the influence of stress concentration on both the stiffness and strength of the scaffolds. The results showed that the pore shape can influence permeability, stiffness, strength, and the stress concentration factor of Ti6Al4V bone scaffolds. Furthermore, the numerical results demonstrate the effect to which structural performance of highly porous scaffolds deviate, as a result of the Selective Laser Melting (SLM) process. In addition, the study demonstrates that stiffness and strength of bone scaffold at a targeted porosity is linked to the pore shape and the associated stress concentration allowing to exploit the design freedom associated with SLM.

Challenges on optimization of 3D-printed bone scaffolds

“…The 3D printing machines, based on the stimulation used for integrating matter, can be categorized into (1) laser-based 3D printing technologies which operate using laser stimulation to bond either material powders or fluid medium; (2) extrusion-based 3D printing technologies which extrude molten materials that either cool and physically bond or are further solidified by UV stimulation, and (3) ink-based 3D printing technologies which print liquid or aerosol chemical binders to chemically bond the material powders together. Laser-based technologies include stereolithography (SLA) [118][119][120][121][122][123][124][125][126][127][128][129][130], selective laser sintering (SLS) [131][132][133][134][135][136], electron beam melting (EBM) [137][138][139], LENS [140], SLM [39,[141][142][143][144][145][146][147][148][149], and two-photon polymerization (2PP) [150,151]. Extrusionbased technologies include fused deposition modeling (FDM) [152], and material jetting (MJ) [96].…”

Effect of nano-Al2O3 addition on the microstructure and erosion wear of HVOF sprayed NiCrSiB coatings

“…Lastly, the material composition of both the powder and the coated surface were investigated using the Energy Dispersive x-ray Spectroscopy (EDS). While there are numerous techniques [61][62][63] to prepare the sample for EDS, a mirror finish grade sequence mechanically polishing and hot resin mounting were the choice of procedure adopted in this study.…”

Porous Scaffold Design for Additive Manufacturing in Orthopedics: A Review

“…The porous structure with suitable pore size and porosity brings enough space for cell proliferation (Kuboki et al, 2001;Zadpoor, 2015). Different pore shapes can lead to altering permeability, which results in different bone ingrowth (Arabnejad et al, 2016;Dallago et al, 2018;Arjunan et al, 2020). The randomly distributed pore is similar to the internal structure of the bone (Liang et al, 2019).…”