Fig. 1: Soluble-core fabrication of the super-elastic conductive fiber through thermal drawing method.

a PVA pellets were reshaped into rods with different shapes by injection molding machine. b To wrap shaped PVA cores with SEBS films. c The prepared preforms after consolidation. d Schematic of the fiber drawing process in the thermal fiber drawing tower. Preforms with different shaped cores were pre-fabricated, and the all-solid preform was heated in the furnace till soft and then drawn into fibers. e Cross-section photos of different shaped PVA cores before and after dissolving the inner cores in water. The inserted scale bars are 200 μm. f Optical image of the resulting fibers. g The microstructure fabricated on fiber surface with the scale bar of 20 μm. h The formation of ultra-flexible conductive fiber. By injecting liquid metal GaIn eutectic alloy into the hollow channel and connecting copper wires on both ends of the fiber as electrodes, an ultra-flexible and ultra-stretchable conductive fiber was formed. A green LED lighted up when connecting to the power source via a piece of conductive fiber that was coiled on a pencil. The inset is the cross-section view of the liquid metal core fiber with the scale bar of 200 μm.