Bio-imitative Synergistic Color-Changing and Shape-Morphing Elastic Fibers with a Liquid Metal Core

The systematic integration of color-changing and shape-morphing abilities into entirely soft devices is a compelling strategy for creating adaptive camouflage, electronic skin, and wearable healthcare devices. In this study, we developed soft actuators capable of color change and programmable shape morphing using elastic fibers with a liquid metal core. Once the hollow elastic fiber with the thermochromic pigment was fabricated, liquid metal (gallium) was injected into the core of the fiber. Gallium has a relatively low melting point (29.8 degrees C); thus, fluidity and metallic conductivity are preserved while strained. The fiber can change color by Joule heating upon applying a current through the liquid metal core and can also be actuated by the Lorentz force caused by the interaction between the external magnetic field and the magnetic field generated around the liquid metal core when a current is applied. Based on this underlying principle, we demonstrated unique geometrical actuations, including flower-like blooming, winging butterflies, and the locomotion of coil-shaped fibers. The color-changing and shape-morphing elastic fiber actuators presented in this study can be utilized in artificial skin, soft robotics, and actuators.