Soft Network Materials With Isotropic Negative Poisson's Ratios Over Large Strains

Auxetic materials with negative Poisson’s ratios have important applications across a broad range of

engineering areas, such as biomedical devices, aerospace engineering and automotive engineering. A

variety of design strategies have been developed to achieve artificial auxetic materials with controllable

responses in the Poisson’s ratio. The development of designs that can offer isotropic negative Poisson’s

ratios over large strains can open up new opportunities in emerging biomedical applications, which,

however, remains a challenge. Here, we introduce deterministic routes to soft architected materials that

can be tailored precisely to yield the values of Poisson’s ratio in the range from 1 to 1, in an isotropic

manner, with a tunable strain range from 0% to ~90%. The designs rely on a network construction in a

periodic lattice topology, which incorporates zigzag microstructures as building blocks to connect

lattice nodes. Combined experimental and theoretical studies on broad classes of network topologies

illustrate the wide-ranging utility of these concepts. Quantitative mechanics modeling under both

infinitesimal and finite deformations allows the development of a rigorous design algorithm that

determines the necessary network geometries to yield target Poisson ratios over desired strain ranges.

Demonstrative examples in artificial skin with both the negative Poisson’s ratio and the nonlinear stress–strain

curve precisely matching those of the cat’s skin and in unusual cylindrical structures with engineered

Poisson effect and shape memory effect suggest potential applications of these network materials.

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