Tuning surface curvatures and young's moduli of TPMS-based lattices independent of volume fraction

Scaffold surface curvature is crucial to guide cell growth and form tissues, and the Young’s modulus of an implant should match the tissue in the implant site. Usually, the curvature and modulus are coupled with volume fraction. Inspired by the lattice slip phenomenon, we propose two structural design methods, linear slip transformation (LST) and rotational slip transformation (RST), to distort an original structure for largely tuning its curvature distribution and Young’s modulus within the restrictions of fixed structural type, volume fraction, and fabricated material. Here samples were additively manufactured using Ti6Al4V. Compared to original triply periodic minimal surfaces (TPMS) based lattices, the curvature distribution spectrum was largely broadened, and negative curvatures were introduced by both LST (generating symmetrical curvature distribution) and RST (generating asymmetrical curvature distribution). Additionally, LST and RST can continuously adjust the Young’s modulus of the original lattice and obtain a drop up to 90 % with 0.3 vol fraction, which can be expected to match soft trabecular bones. Interestingly, the resulting structures show elastic anisotropy and slip-induced deformation. The proposed approaches can be applied to biomedical applications and used to adjust lattice properties for use in energy, aerospace, and optics.