Mudassar Khalil

This paper was presented at the June 2024 NAFEMs Conference. NAFEMS is the International Association for the Engineering Modelling, Analysis and Simulation Community.

Metallic scaffolds are used as implants to help heal bones. Sheet-based Triply
Periodic Minimal Surfaces (TPMS) are of interest due to their high surface-to-volume ratio (S/V), customisable stiffness, and can be realised using Additive Manufacturing (AM). Other studies investigate porosity and pore size of scaffolds but they frequently overlook S/V, which is critical for cellular response. Additionally, the limitation of AM (esp. Selective Laser Melting (SLM)) causes discrepancies between intended and actual physical and mechanical properties of those structures, and this also needs to be addressed. This work investigates three types of TPMS scaffolds made in pure Titanium, with an emphasis on design vs manufactured differences and the significance of S/V. As-designed scaffolds reported 70-75% porosity and 25-35 cm-1 S/V, and stiffness was measured using finite element analysis (FEA) at 6.7-9.3 GPa. The manufactured scaffolds had 59-70% porosity and 33-42 cm-1 S/V. Laboratory compression testing revealed an effective Young’s modulus of 5-9 GPa, comparable to bone. Image-based simulation method was also employed on the built samples which reported the stiffness range of 8.3-16.6 GPa, overestimating it by 57%. It is hypothesised that these discrepancies stem from the secondary roughness deposited on the scaffold walls during SLM, causing reduction in porosity yet not contributing to structure’s strength. The cyber physical validation methods presented are a good way to quantify these
discrepancies, allowing feedback to the design stages for more predictable as manufactured structures.

https://www.nafems.org/publications/resource_center/uk24_ext_abs_18

M. Khalil, M. Burton, S. Hickinbotham, P. P. Conway, C. Torres-Sanchez

Published in the Engineering Modelling Analysis & Simulation – The NAFEMS Journal Vol. 2, Issue 1, 2025

Abstract

Metallic scaffolds are used as implants to help heal bones. Sheet-based Triply Periodic Minimal Surfaces (TPMS) are of interest due to their high surface-to-volume ratio (S/V) and customisable stiffness. They can be realised using Additive Manufacturing. Other studies investigate porosity and pore size of scaffolds, but they frequently overlook S/V, which is critical for cellular response. Additionally, the limitation of AM (esp. Selective Laser Melting (SLM)) resides in the discrepancies between as-designed and as-built physical and mechanical properties of those structures, and this also needs addressing. This work investigates three types of pure Titanium TPMS scaffolds, with an emphasis on as-designed vs as-built discrepancies and the significance of S/V. As-designed scaffolds reported 70-75% porosity and 25-35 cm^-1 S/V, and stiffness was measured using finite element analysis (FEA) obtaining 6.7-9.3 GPa. The as-built scaffolds had 59-70% porosity and 33-42 cm^-1 S/V. Laboratory compression testing revealed an effective Young’s modulus of 5-9 GPa, comparable to bone tissue. Image-based simulation methods were employed on the as-built samples which reported the stiffness range of 8.3-15 GPa, overestimating it by 54%. It is hypothesised that these discrepancies stem from the secondary roughness on the surfaces, cracks and entrapped voids created during the SLM process, causing reduction in porosity, yet not contributing to structure’s strength. The cyber-physical validation methods presented in this work are a good way to quantify these discrepancies, allowing feedback to the design stages for more predictable as-built structures.

This Conference Paper was given by Mudassar Khalil at the 3rd World Congress on Artificial Intelligence in Materials and Manufacturing (AIMM 2025).

The Additive Manufacturing Meets Medicine Scientific Conference was focused on the intersection of 3D printing technology and medical engineering. Organized by Infinite Science GmbH, this conference took place at the prestigious Fraunhofer IMTE in Lübeck, Germany. Its aim was to serve as a platform for engineers, scientists, technicians, physicians, and entrepreneurs to come together and explore the latest advancements in the field of 3D printing as it pertains to medicine. As the use of additive manufacturing continues to expand in medical applications, this conference was to highlight its transformative potential in creating prostheses, soft implants, and matrices for tissue engineering.

Published in “Transactions on Additive Manufacturing Meets Medicine Trans. AMMM, 2025, Vol. 7, No 1, Article ID 2086”

https://doi.org/10.18416/AMMM.2025.25062086

Abstract: Bioengineered scaffolds with optimized osteoconductive and osteoinductive properties are highly desirable in bone tissue regeneration. Stochastic porous structures, resembling human trabecular bones, have gained increasing attention due to their suitability and superior performance in bone healing compared to regular porous architectures. In this study, we designed six trabecular-like porous scaffolds with varying porosity and surface area-to-volume ratios. The scaffolds were fabricated using pure titanium via selective laser melting, and their morphological characteristics were analyzed via micro computed tomography. Quasi-static compression testing was conducted to assess mechanical properties. The results showed that the as-built scaffolds exhibited a porosityrange67–71%, an average pore diameter ranging440–565 μm, a quasi-elastic gradient between2.6–3.5 GPa, and a yield strength of 44–58MPa. These values closely match those of the cortical bone, indicating potential for orthopeadic applications by mitigating stress shielding and enhancing implant longevity. Additionally, the permeability and wall shear stress were measured to predict cell growth performance in the scaffolds. The as-built models have a satisfactory permeability range of 6×10−9to 15×10−9m2, which is higher than that of cancellous bone, benefitting prospects for nutrient flow and by-product removal that encourage osteoblastic mineralization

This Conference Presentation was given by Mudassar Khalil at the 3rd World Congress on Artificial Intelligence in Materials and Manufacturing (AIMM 2025).

The Additive Manufacturing Meets Medicine Scientific Conference was focused on the intersection of 3D printing technology and medical engineering. Organized by Infinite Science GmbH, this conference took place at the prestigious Fraunhofer IMTE in Lübeck, Germany. Its aim was to serve as a platform for engineers, scientists, technicians, physicians, and entrepreneurs to come together and explore the latest advancements in the field of 3D printing as it pertains to medicine. As the use of additive manufacturing continues to expand in medical applications, this conference was to highlight its transformative potential in creating prostheses, soft implants, and matrices for tissue engineering.