Topological design, mechanical responses and mass transport characteristics of high strength-high permeability TPMS-based scaffolds

A strategy of controlling the topology structure of triply periodic minimal surface (TPMS)-based scaffolds (CTTS) was proposed in this study to cater to the mechanical and biological requirements. Two new types of TPMS-based scaffolds called AD and AG were designed on the basis of diamond (ID) and gyroid (IG). The topology structures of ID and IG were changed by manipulating the trigonometric functions in the expressions. AD and AG retained the advantageous structural characteristics of ID and IG, such as high wall surface area and good connectivity. However, they differed in terms of pore shape and size. The gradient density ID (FD) and the gradient density IG (FG) were designed for comparison. The porosities of ID, IG, FD, FG, AD, and AG were set to 60, 70, and 80%. Compressive simulations and computational fluid dynamics simulations were conducted for the designed scaffolds. AD with 80% porosity (AD80) and FD with 80% porosity (FD80) were manufactured through electron beam melting. Their morphological features were characterized through microcomputer tomography scanning and scanning electron microscopy. Compression and fall head tests of AD80 and FD80 were performed. In combination with the numerical results, the geometrical parameters, manufacturing accuracies, mechanical properties, permeability, and flow behavior of each scaffold were systematically analyzed. Results show that with the same porosity, the manufacturing accuracies and the permeability of AD and AG are higher than ID, IG, FD, and FG. The mechanical properties of AD are higher than other scaffolds. Although the wall surface area of AD is smaller than ID and FD, it is still larger than IG and FG, which can provide sufficient space for cell adhesion. AD is an appropriate candidate for solving the contradiction between sufficient mechanical properties and high permeability and exhibits excellent biological property.