Liquid Metal Fibers

Liquid metal (LM) is a type of metal or alloy that has a low melting point near room temperature and exhibits the properties of both liquids and metals. Such unconventional materials have been gaining increasing attention within the scientific and industrial communities. Recently, fiber-shaped LM and its composites have especially attracted diverse interest owing to their unique merits, such as excellent conductivity, intrinsic stretchability, facile phase transition, and the ability to be woven or knitted into smart fabrics. This review is dedicated to summarizing different aspects of LM-based fibers, such as their material components, fabrication and design strategies, and remarkable applications by way of their representative properties. Typical fabrication approaches, such as 3D printing of pure LM wire, coating the LM shell on the surface of the fiber, injecting a LM core into hollow fibers, and spinning of LM and polymer hybrids have been comparatively illustrated. Moreover, emerging applications that primarily utilize LM fibers have been demonstrated. Finally, future directions and opportunities in the field are discussed. This categorization of LM fibers is expected to facilitate further investigation and practice in the coming society.Graphical AbstractTOC: Schematic illustration of liquid metal fibers and their fabrication technologies: 3D printing, coating of liquid metal on fibers, injection of liquid metal into hollow fibers, spinning of LM composites. Liquid metal fibers can be applied as stretchable electronics, smart clothing, health monitoring, electrical switches, and shape memory devices.