Design Strategies for Mixed Unit Cell Lattices: Mechanical Assessment with Biomedical 3D Printing

3D printed lattices have efficient mechanics for wide-ranging engineering applications, especially biomedical domains. In bone tissue engineering, lattices constructed from unit cells enable tunable mechanics and tissue growth by altering unit cell beam diameters and porosity suitable for design personalization. Heterogeneously mixing unit cells throughout lattices is a promising tuning strategy; however, there remains a need for further systematic investigation linking design decisions to mechanical outcomes. In this study, biocompatible photopolymer resin is used to print Cube, BC (Body-Centered), and BC–Cube lattices with approximately 75% porosity. When tested in compression, these lattices have Elastic Moduli of 202 ± 5.4, 30 ± 1.6 MPa, and 97 ± 4.0 MPa, and yield stresses of 6.0 ± 0.11, 1.1 ± 0.07, and 3.1 ± 0.13 MPa, respectively. Heterogeneous lattices with Cube and BC unit cells in stochastic mixtures (25/75, 50/50, 75/25) and four deterministic layouts (Layers 0°, Layers 90°, Rows 0°, Rows 90°) with equally proportioned unit cells were also designed. Stochastic mixing produced a linear relationship between the Elastic Modulus and Cube unit cell proportion (R2 = 0.98), consistent with a rule-of-mixtures. Deterministic heterogeneous layouts bypassed the rule-of-mixtures, with Elastic Moduli spanning 97.6 to 163.4 MPa, with select designs outperforming stochastic configurations. Findings demonstrate the merits of heterogeneous strategies to improve lattice designs, with suitability for biomedical applications.