Tailoring 3D Buckling and Post Contact in Microlattice Metamaterials

Abstract

Mechanical metamaterials have been established as the paragons of enhanced mechanical performance, due to their properties inherited by their architected microstructure. The rapid progress in additive manufacturing has enabled the fabrication of complex geometries even at the microscale, with nanoscale features. For the case of ultra-light, ultra-stiff mechanical metamaterials, the high stiffness and increased energy dissipation is associated with the controlled buckling and subsequent post contact of the lattice members. In addition, architected defects, scaled up in the microscale, inspired by the structural defects in the crystal structure, have accomplished tailoring the plasticity mechanisms and localized deformation in a similar manner as slip planes through dislocation motion and vacancies in bulk crystalline materials. This chapter will focus on the design principles that must be addressed to effectively fabricate novel geometries possessing these intrinsic properties. These principles will be instantiated through the design of intertwined microlattices, inspired by crystal in-growth mechanisms, and architected 3D vacancies, inspired by crystal defects. All of the structures were fabricated through multiphoton lithography, the most suitable technique for fabrication of complex geometries at the micrometer-nanometer length scale. Through finite element analysis and nanoindentation experiments, we delineate how the mechanical behavior is manifested and can be tailored.