Freely Deformable Liquid Metal Grids as Stretchable and Transparent Electrodes

Abstract

A new structure of stretchable and transparent metal-grid electrodes is described, where a liquid metal alloy, eutectic gallium–indium (EGaIn) is employed as a stretchable conducting material. By a “roll-painting and lift-off” technique based on photolithography, stretchable EGaIn-grids with the linewidth of 20 $\mu \text{m}$ and the line pitch of 400–1000 $\mu \text{m}$ are produced, providing the transmittance of 75%–88% with the sheet resistance less than 2.3 $\Omega $ /square. Powered by the freely deformable nature of the liquid phase conductor, the EGaIn-grid provides stable conductivity under highly stretched condition up to 40%, as well as high reliability against cyclic deformation. By combining the EGaIn-grid with a homogeneous and transparent poly(3,4-thylenedioxythiophene):poly(styrensulfonate) (PEDOT:PSS) layer in a hybrid manner, we can construct highly stretchable and uniformly conducting transparent electrodes. The hybrid PEDOT:PSS/EGaIn-grid electrodes can be utilized as electrodes for a stretchable inorganic electroluminescence device with a ZnS phosphor-elastomer composite as the emission layer, which maintains uniform and stable emission under highly and repeatedly stretched conditions.