A microfabrication approach for making metallic mechanical metamaterials

Highlights: • A low cost, rapid throughput micromachining technique for scalable manufacturing of sub-millimeter metamaterials is developed. • Sensitivity of lattice properties to manufacturing precision is investigated via assessment of geometric imperfections. • Lattice properties are competitive with those of counterparts fabricated via various additive manufacturing methods. • The developed approach provides a new route for synthesis of sub-millimeter metamaterials from a wide variety of materials. A scalable technique for making octet microlattice topology mechanical metamaterials with a cell size of 1 mm or less from thin stainless steel sheets is described. The microfabrication process used a perforation operation to form planar truss sheets by the periodic removal of rectangular shaped material. A simultaneous perforation and corrugation operation was also used to create a single layer of trusses with a pyramidal topology. A 3D lattice was then assembled by alternatively stacking the pyramidal and planar truss sheets, taking care to align their nodes to form the octet lattice truss topology. A vacuum brazing method was used to metallurgically bond the assembly. The compressive properties of the microlattices are shown to be comparable to those of much larger cell-size structures of similar material and topology. An assessment of geometric imperfection sensitivity indicates where further mechanical property improvements could be realized by improving the precision of both the perforation and assembly process.