Ultrastretchable Thermo- and Mechanochromic Fiber with Healable Metallic Conductivity

This work demonstrates a facile way to fabricate ultrastretchable thermo- and mechanochromic fiber with healable metallic conductivity. Thermochromic hollow elastic fiber is prepared by using silicone composite with thermochromic pigment. Once the fiber forms, gallium-based liquid metal is injected into the fiber. The composite fiber with liquid metal core shows uniform color change along the fiber by applying Joule heating through the liquid metal wire. The fiber with multiple thermochromic pigment locally distributed along the fiber shows serial color change by increased current. The healable conductivity of the metal core is demonstrated by restoring electrical conductivity near room temperature. When it is in a solid state, the wire can fracture during deformation, thus the wire loses conductivity. However, upon body heating, the wire can rewire, because of the low melting point of the metal (gallium, 29.8 °C). This healing ability of the metal core can allow the fiber to have healable thermochromic behavior. Stretching a liquid metal wire can change the geometry of the wires, resulting in a color change because of increased resistance while Joule heating is applied. This thermo- and mechanochromic fiber with liquid metal core would find use in wearable and conformal electronics, electronic textiles, and soft robotics.