Controllable and\nFacile Metallization of Polymer Surface\nwith Biphasic Liquid Metals toward Soft Circuits

Chemical metallization (e.g., chemical/electrical plating)\nof the\npolymer surface is an extremely important, convenient, cost-effective,\nand broadly applied strategy to realize combined advantages of functional\nmetals and polymers for today’s industry. However, traditional\nchemical and electrical metallization of polymer surfaces requires\nthe participation of physical methods, which greatly constrains the\nutilization of versatile metals in modern electronics. This work successfully\nutilized a traditional chemical strategy to address the challenging\npreliminary conductivity and subsequent liquid metal (LM) metallization\nof insulated polymer surfaces. Through the facile strategy, an ultrathin\n(6 μm) LM film could be conveniently coated on both the external\nand internal surface of polymers to fabricate large-area flexible\ncircuits with fine line width (15 μm) at low-cost (9.5 $·dm<sup>–2</sup>). A detailed reaction mechanism of the LMs was reported,\nand various chemical parameters of the metallization were thoroughly\ninvestigated. Interestingly, the metallized polymer surface showed\na distinguished CuGa<sub>2</sub>/Ga biphasic structure of the LMs,\nwhich enabled the polymer as an extraordinarily soft conductor with\nultrahigh uniaxial strain (>1200%), extremely low resistance variation\n(<i>R/R</i><sub><i>0</i></sub> < 7), strong\nmetal–polymer adhesion (1.5 N·mm<sup>–1</sup>),\nand excellent electrical durability. Furthermore, with the benefit\nof the photolithography technique, precisely designed circuits could\nbe achieved, and wireless transmission/control soft electronic devices\nwere easily fabricated.