Highly conductive sheath–core structured liquid metal fibers with invariant resistance under high tensile strength

• Flexible conductive fibers with a sheath-core structure were prepared using coaxial wet spinning. The sheath-core structure effectively protects the conductive core layer, resulting in low fiber resistance. Moreover, the resistance of the conductive fibers is insensitive to strain, maintaining a low value even under tensile conditions. • The fibers exhibit an excellent Joule heating effect, where the application of a small DC voltage to the conductive fibers causes a noticeable temperature increase. When the voltage is kept constant, the fibers maintain a stable temperature, and the fiber temperature is proportional to the applied voltage . As the voltage increases, the fiber temperature shows a stepwise increment. • The conductive fibers were woven into a fabric that exhibits excellent thermal stealth and electromagnetic wave shielding capabilities. When the fabric covers the surface of an object, infrared thermal imaging reveals minimal temperature contrast between the fabric and the object. Additionally, analysis using a vector network analyzer indicates that the fabric possesses outstanding electromagnetic wave shielding performance. With rapid advancements in military, information, and environmental protection technologies, electromagnetic wave-shielding and thermal stealth materials have drawn significant attention. The development of flexible electronic technology has driven the demand for smart fibers with exceptional electrical conductivity, flexibility, and elasticity. To address these requirements, we developed a sheath–core structured liquid metal flexible smart conductive fiber with high strain-insensitive conductivity using a coaxial wet spinning technique. In addition, we investigated fiber activation modes, including freeze activation, pressure activation, and freeze–pressure activation. After activation, the fiber achieved a conductivity of 4.12 × 10 4 S m -1 and a stretchability of up to 516 %. Further, the fiber fabric exhibited an electromagnetic wave-shielding effectiveness of 37.51 dB. Under 100 % strain, the activated flexible conductive fibers achieved a minimal resistance variation of only 2.99 %, demonstrating outstanding conductivity and strain-insensitive electrical performance. These smart fibers, characterized by their high conductivity, flexibility, and elasticity, present an innovative solution to various challenges encountered in smart wearable technologies.