DNA-silica nanolattices as mechanical metamaterials

Mechanical metamaterials consist of intricate periodic structures made using additive manufacturing techniques. Yet, nanoscale (<10 nm) features cannot be directly printed using these fabrication techniques, although this is the size regime in which enhanced material properties appear. In addition, current additive manufacturing techniques cannot easily combine disparate materials (e.g., soft, biological polymers with hard ceramics) into structural motifs. Here, we show that DNA origami can be used to construct octahedral-based isotropic and anisotropic nanolattices. When coated with a thin silica layer, these nanolattices obtain strength and energy absorption competitive with the best additively manufactured nanolattices. The DNA nanolattices have strut 6 nm diameters and  ~50 nm unit cells, which are two orders of magnitude smaller than lithography-based lattices. The silica coating is as thin as ~1.65 nm, which results in enhanced strength. Atom probe tomography confirms the nanoscale distribution of DNA and silica in the octahedral lattice geometry. Finite element modeling (FEM) reveals two dominant failure modes: buckling at lower coating thicknesses and tensile fracture at higher thicknesses. Molecular dynamics (MD) simulations reveal that the DNA delays failure by suppressing buckling within the lattice struts, while the nanoscale silica undergoes a surface buckling mode which contributes to increased strength at large strains.