A One‐Step Fabricated Sheath‐Core Stretchable Fiber Based on Liquid Metal with Superior Electric Conductivity for Wearable Sensors and Heaters

Abstract Conductors with high conductivity and stretchability are the crucial components of smart wearable electronics. However, most of the reported conductors have disadvantages of single function, high energy consumption, which seriously limit their application in wearable electronics. Here, a kind of stretchable (up to 373%), highly conductive (the same order of magnitude as commercial metal wire), and multifunctional sheath‐core fibers based on liquid metal that can be continuously fabricated in large quantity through a coaxial wet‐spinning process are reported. The simple preparation method of the fibers can realize continuous and mass production (1 m min^–1 in the laboratory). When the fibers are used as an electric heater, the temperature can reach 58 °C at 0.6 V and the heating rate is obviously faster than the ambient temperature under infrared light. When the fibers are used as a wearable sensor, the tiny force of 0.001 cN can be detected and objects at less than 40 cm can be detected without contact. The stretchable fibers with high electric conductivity may provide strong supports for the commercialization of wearable electronics and pave the way toward full‐fledged multifunctional wearable sensors.