Auxetic Two-Dimensional Nanostructures from DNA

Abstract

Architectured materials exhibit negative Poissons ratios and enhanced mechanical properties compared with regular materials. Their auxetic behaviors should emerge from periodic cellular structures regardless of the materials used. The majority of such metamaterials are constructed by top-down approaches and macroscopic with unit cells of microns or larger. On the other extreme, there are molecular-scale auxetics including naturally-occurring crystals which are not designable. There is a gap from few nanometers to microns, which may be filled by bottom-up biomolecular self-assembly. Here we demonstrate two-dimensional auxetic nanostructures using DNA origami. Structural reconfiguration experiments are performed by strand displacement and complemented by mechanical deformation studies using coarse-grained molecular dynamics (MD) simulations. We find that the auxetic properties of DNA nanostructures are mostly defined by geometrical designs, yet materials chemistry also plays an important role. From elasticity theory, we introduce a set of design principles for auxetic DNA metamaterials, which should find diverse applications.