Bidirectional Zero Poisson's Ratio Elastomers with Self-Deformable Soft Mechanical Metamaterials for Stretchable Displays

Abstract

Stretchable displays, capable of reversible expansion, represent significant advancements in free-form display technologies. However, the high Poisson's ratio (nu) of elastomer substrates leads to unintended deformation under tensile strain, resulting in image warping. To address this, a meta-elastomer (ME) substrate with a bidirectional zero nu, incorporating a self-deformable soft mechanical metamaterial (MM) frame, is introduced. The nu of the ME is precisely programmed by the interaction between the deformation of the MM frame, which exhibits a negative nu, and the elastomer matrix, which has a positive nu. The soft MM frame, stiffer than the elastomer matrix, undergoes both structural deformation and length alteration during substrate tensile strain. This synergistic effect enables achieving a nearly bidirectional zero nu, thus overcoming the limitations of conventional tessellated rigid MM composites. Furthermore, the ME substrate, which is chemically cross-linked at the junction interface, demonstrates exceptional mechanical robustness, enduring over 180% stretching and more than 10 000 cycles. By counteracting the Poisson's effect, the ME substrate with an integrated pixel array ensures translational pixel movement along the tensile axis during bidirectional stretching, minimizing undesired pixel movement in other directions. The stretchable ME presents key advancements for implementing more stable and reliable stretchable display applications.