Three-Dimensionally Printed Mechanical Metamaterials With Thermally Tunable Auxetic Behavior

Mechanical metamaterials exhibiting negative Poisson's ratio (expanding, rather than contracting, in the direction perpendicular to an applied force) typically do not retain the ability to behave as typical materials with positive Poisson's ratio, which restricts their application where adaptive behavior is desirable. This work demonstrates dynamic, on-demand regulation of auxetic behaviors in mechanical metamaterials, through a combination of structural design and multimaterial three-dimensional printing. The design principle provides a further degree of freedom for metamaterials exhibiting extraordinary and programmable mechanical behaviors.