Highly Conductive Omnidirectionally Stretchable 2D Transparent Copper Mesh Electrodes and Applications in Optoelectronic Devices

2D stretchable transparent electrodes (STE) are required to conform to non-flat complex 3D surfaces for next-generation stretchable optoelectronic devices. However, it is a great challenge to simultaneously maintain omnidirectional stretchability, high transmittance, and the least change in conductivity at large strain. In this work, omnidirectionally stretchable 2D transparent electrode is achieved by hybrid printed copper mesh embedded in an elastic material. The electrode displays exceedingly low sheet resistance down to 0.12 omega sq(-1) while still maintaining 80% of optical transparency. Two types of mesh geometries, the horseshoe-like and sinusoid-like shapes, are thoroughly investigated by simulations and experiments. By optimizing the key geometrical parameters of mesh structure, the copper mesh can endure stretching up to 130% with no fractures and no resistivity change. After 1000 stretch-and-release cycles at 10% strain, the copper mesh remains intact with negligible resistance variation. For 2D stretchability, the copper mesh is stretched in eight directions simultaneously and can maintain its initial conductivity up to 50% tensile deformation. As a demonstration of application, the copper mesh STE is employed in a stretchable electroluminescent device that maintained uniform lighting up to 120% stretching and 100 stretch-release cycles at 30% strain, showing its potential in stretchable and wearable optoelectronic applications.