Auxetic Two-Dimensional Nanostructures from DNA

Abstract

Architectured materials exhibit negative Poisson’s ratios and possess enhanced mechanical properties compared with regular materials. Their auxetic behaviors emerge from periodic cellular structures rather than chemistry. 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 (2D) auxetic nanostructures using DNA origami. Structural deformation 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 a role. From elasticity theory, we introduce a set of design principles for auxetic DNA materials which should be useful for diverse applications.

DNA Nanostar Structures with Tunable Auxetic Properties

“…The rotation with  = -1 is consistent with that of other centrosymmetric designs such as rotating squares. 17 Overall, the auxetic properties of the sliding stars can be modulated by directing the sliding behaviors into a desired combination.…”

“…This method is efficient for material usage and allows for designing larger structures with a limited number of nucleotides (nt). 41 To enhance the stiffness of the edges of the stars, we followed the principles previously described by Li et al 17 They demonstrated that edge thickness t must be sufficiently large for a given length L and ss-joints at vertices must experience a certain level of tension (termed joint stretch η) in order to avoid significant flexure or distortion during reconfiguration. Our edges and joints are designed with four duplex bundles (t/L ≈ 0.1) and a stretch level of η ≈ 55% to meet the design requirements.…”

“…We followed the same procedure for sample preparation and measurement as previously described. 17 The lengths of edges and the angles at vertices were measured and matched with our designs.…”

“…16 Recently, Li et al bridged this gap in lengthscale. 17,18 In their studies, nanoscale auxetic units were constructed using DNA origami exploiting sequence complementarity of DNA molecules. DNA self-assembly has been developed as a powerful bottom-up strategy with excellent programmability and precision 19 and demonstrated for complex architectures, [20][21][22][23][24] reconfigurable designs, [25][26][27][28] and dynamics processes.…”

Topological Assembly of a Deployable Hoberman Flight Ring from DNA

“…The flight ring is unique in that its structure is finite, while other typical auxetic geometries are periodic, extended in 2D or 3D. 27,28 In closing, Hoberman flight rings are realized using DNA origami, which forms a left-handed trefoil knot. The deployable and auxetic nanostructures may serve as a versatile platform for topological studies and open new opportunities for bioengineering and biosensors such as highprecision drug delivery 29 and molecular targeting and swallow 30 .…”