When Scale Matters: Size‐Dependent Mechanics of Architected Lattices for Implants and Beyond

Architected materials offer bright possibilities to achieve specialized mechanical properties that are not possible with most engineering and natural materials. For example, they allow the design of personalized metal medical implants with reduced stress shielding and improved implant longevity. However, the interplay between the characteristic length scales of a microscopic architecture and macroscopic dimensions can significantly alter the mechanical response of such implants. Here, we systematically investigate geometric size effects in cellular lattices and mechanical metamaterials under fundamental compressional, shear, and torsional loads for representative unit cell designs. Using finite element simulations, we analyze how variations in the size of a unit cell affect the effective elastic moduli of the lattices and validate our findings experimentally. We further apply these insights to analyze the mechanical behavior of a simplified metamaterial implant under complex loads and various interfacial conditions between the bone and the implant. Our results identify critical relations between the size effects parameters and the mechanical properties of cellular lattices and metamaterials. We highlight the importance of cell size in geometrically constrained applications and propose a procedure for a full‐scale discrete analysis of size effects. Our findings lay the groundwork for the advancement of higher‐order continuum theories and will help drive the adoption of metamaterials across a wide range of engineering applications.