Hybrid auxetic metamaterial platforms enabling multiscale isotropic expansion for distortion-free stretchable displays.

Stretchable displays suffer image distortion due to transverse compression of substrates under uniaxial stretching. Although auxetic frameworks with negative Poisson's ratios, which expand vertically during horizontal stretching, offer promising solutions, their void-rich structures are unsuitable for displays, requiring hybrid integration with continuous elastomeric substrates. This integration is challenging because rotational motions essential to auxetic unit cells can induce local substrate deformation, while the substrate can also restrict rotation, undermining auxetic performance. Here we show that design methodologies for hybrid auxetic metamaterial platforms, in which auxetic frameworks and elastomeric substrates are bonded at selective sites optimized for both horizontal and vertical stretching, enable isotropic expansion across local-to-global scales. To this end, the isotropic expansion factor is introduced as a statistical metric for quantifying image distortion. With the proposed hybrid platforms, we demonstrate stretchable displays exhibiting uniform, distortion-free expansion and stable performance under repeated stretching.