Direct Writing and Repairable Paper Flexible Electronics Using Nickel–Liquid Metal Ink

Liquid metals such as gallium and its alloys can be printed on various substrates to form electronic circuits. However, up to now there are still few methods for the direct writing of liquid metals on common printed paper. Here, a novel conductive material prepared by adding metal powder to a gallium alloy is introduced. The proposed material exhibits low liquidity, excellent plasticity, significantly enhanced adhesivity to paper substrates, which guarantee the stable and flexible electrical connection. The oxide film wrapping the nickel powder forms a skeleton for additional oxidation products, resulting in superior adhesion to paper. In addition, several paper flexible electronic applications are showcased to demonstrate the practical value and reparability of this material. This work paves the way for the design of a facile method of preparing paper electronics.