Soft network materials with isotropic negative Poisson's ratios over large strains

Abstract

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.

Star-shaped metrics for mechanical metamaterial design

“…Metamaterials can even have properties that are not commonly found in nature, as in the case of auxetic metamaterials, i.e. materials with a negative Poisson's ratio that will expand transversally when stretched along a give direction [Babaee et al 2013;Kolken and Zadpoor 2017;Lakes 1987;Liu and Zhang 2018]. As such, they are of great interest to engineers and material scientists and actively studied in these communities.…”

Geometric Mechanics of Origami Patterns Exhibiting Poisson’s Ratio Switch by Breaking Mountain and Valley Assignment

“…1), thus behaving as a single material possessing both positive and negative Poisson's ratio. The Poisson's ratio switching is an enticing phenomenon that has only been found recently for selected mechanical metamaterial designs, including nanoplates [14], re-entrant origami tube assemblages [15], bistable auxetics [16], kirigami structures [17] and soft networks [18]. Compared to other designs, the Morph excels on having a wider tunable range of Poisson's ratio, theoretically from negative infinity to positive infinity.…”

Progress in Auxetic Mechanical Metamaterials: Structures, Characteristics, Manufacturing Methods, and Applications

“…Utilizing this technique, 2D and 3D chiral AMMs have been made from single photosensitive material. [39,44,52,124] To enhance the auxetic behavior and mechanical properties of AMMs, some researchers have fabricated re-entrant structures [59,125,126] and missing ribs [38] by the multimaterial PolyJet technique, which could simultaneously print more than two types of materials in one part. Compared with 3D re-entrant auxetic metamaterials with single material, dual-material auxetic metamaterials have stable NPR at large strain.…”