Elastic and failure characterization of hydroxyapatite TPMS scaffolds using a combined approach of ultrasound, compression tests and micro-CT based numerical models

Abstract

Hydroxyapatite is a widely used ceramic material for bone tissue engineering. For creating suitable scaffolds, reliable design and thorough characterization are essential. In this study, we designed and 3D printed three Triply Periodic Minimal Surface (TPMS) scaffold geometries using Vat Photopolymerization (VPP). We employed a combined experimental and numerical analysis approach to evaluate printing accuracy and its correlation with the mechanical properties of the scaffolds. Our findings indicate that VPP can print complex micro-architectures as those of the TPMS with thin wall thickness in the range of few hundreds of micrometers. Ultrasound waves and compression tests were conducted to determine the effective stiffness and strength of scaffolds, respectively. Finite Element Models were developed based on Computed micro-Tomography acquisitions to simulate the experimental compression tests, showing strong alignment with the experimental data. Among the tested TPMS geometries, the Diamond microstructures fail with the lowest specific strength, while the highest specific strength is shown by the I-graph and wrapped package-graph (IWP) scaffolds.