Depth-Modulus Engineered Meta-Elastomers for Multiaxial Strain Programming in Stretchable Displays

Abstract

With the growing demand for displays with diverse form factors, stretchable displays are at the forefront of this evolution garnering significant interest. One challenge is image warping caused by the high Poisson's ratio (nu) of conventional elastomers during stretching, meta-elastomer (ME) substrates incorporating high-modulus mechanical metamaterial frames with a negative nu have emerged as promising solutions. However, the modulus mismatch between the frame and matrix results in undesirable thickness variations in ME substrates under tensile stress, degrading image quality by distorting the focal length. In this study, depth-modulus engineered MEs that achieve near-zero nu under multiaxial strain are reported. By infiltrating a vaporized cross-linker, a continuous depth-modulus gradient in the ME substrates is created, effectively minimizing Poisson's effects and z-axis deformation simultaneously. These continuous gradient depth-modulus engineered ME (C-GDME) substrates reduce the in-plane nu to 0.09 and exhibit thickness variation close to half that of pristine ME substrates without modulus tailoring. Furthermore, C-GDME substrates demonstrate excellent mechanical durability and approximate to 90% visible-light transmittance. The integrated light-emitting diode arrays on the C-GDME substrates display linear and predictable pixel displacement under stretching, highlighting their potential for stretchable displays.