Liquid metals are a class of metals that are fluids at room tem-perature.They have surface tension,that is approximately an order of magnitude higher than that of water,owing to the high surface energy of metals.The ultra-high surface tension creates a stream of liquid metal droplets to minimize surface energy,and therefore,creating other shapes is difficult.Enormous efforts have been made to manipulate liquid metals into various shapes and patterns,and are driven by emerging opportunities for soft,stretchable and reconfigurable electronic and electromagnetic devices[1,2].For instance,to form tailor-designed conductive patterns,liquid metal is smeared onto a soft substrate[3],injected into channels and molds[4],or liquid metal droplets are stacked into 3D architectures[5].To facilitate the printing of liquid metal,it is either enveloped by a viscous sheath fluid[6],or formulated into pastes by adding large amounts of nanoparticles[7].