Gallium-Based Liquid Metal Composites for Flexible Sensors: Design Strategies, Sensing Functions, and Application

In recent years, flexible sensors have played an important role in fields of medical diagnostics and soft robotics for their unique conformability. To further improve the sensing performance, new strategies involving liquid metal-based composite materials have shown many advantages. Among the emerging new materials, gallium-based liquid metals stand out as an ideal candidate for flexible sensors, thanks to their high electrical conductivity, high stretchability, and excellent biocompatibility. In this review, recent progress of gallium-based liquid metal composites–enabling flexible sensors is summarized. First, fundamental properties of gallium-based liquid metals are introduced; second, compositional and structural designs of various liquid metal composites predominantly based on gallium alloys are described. Third, a variety of functional sensors, with applications ranging from strain measurement to pH testing, are presented. Fourth, representative emerging applications of flexible sensors are highlighted. Lastly, key challenges and future opportunities of liquid metal composites for flexible sensors are discussed.