Liquid Metal Covered with Thermoplastic Conductive Composites for High Electrical Stability and Negligible Electromechanical Coupling at Large Strains.

Stretchable electrode is an essential part of soft electronic devices. Practical stretchable electrodes must meet the following requirements; metallic conductivity and no resistance change in various situations such as repeated large deformation, toxic environment, and large temperature change. This study suggests a simple electrode design that meets all the requirements simultaneously. The electrode consists of a liquid metal (LM) mesh pattern that is sandwiched between a thermoplastic block copolymer (BCP) film and a BCP/Ag flake composite film with a microfibril network structure on its surface. The electrode has a high conductivity (1.2 x 10^4 S/cm) and is stretchable up to 600% uniaxial strain (ε). Its resistance maintains unchanged during repeated stretching cycles at ε = 300% (ΔR < 0.04 Ω), and also under simultaneous situation of large deformation (ε = 400%) and large temperature change (20 ºC-70 ºC). The electrode is anti-corrosive in an acidic solution owing to the hydrophobic BCP layer that protects the LM from being etched. This study shows the connection of two separate electrodes and complete healing of scratched electrodes by finger pressing. In addition, it demonstrates the fabrication of superstretchable electroluminescence display as an example of potential uses of the electrode.