Gallium-based liquid metals (LMs) featuring both high conductivity and fluidity are ideal conductors for soft and stretchable electronics. However, their liquid nature is a doubleedged sword in many key applications since LMs are inherently prone to mechanical damage. Although additional encapsulation is frequently used for the protection of delicate LM electrodes, it hinders the electrical interfacing with other objects for interconnection, sensing, and stimulation. Here, different from conventional patterning methods that deposit LM on or inside substrates, we for the first time report a simple strategy to create surface-embedded LM of eutectic gallium-indium (EGaIn) circuits with mechanical damage endurance. This was achieved by using direct magnetic printing to overcome the high surface tension of LM, allowing it to be passively filled into the laser-patterned microgrooves on soft substrates. We show that the surface-embedded LM circuits are resistant to mechanical erasure, washing, and peeling. We also show the applications of our surface-embedded LM electrodes in respiration monitoring and electrical stimulation of nerves. This work provides a simple and efficient way to create mechanically reliable LM microelectrodes, holding great promise for wearable and implantable bioelectronics.

Conductive and stretchable fibers are the cornerstone of intelligent textiles and imperceptible electronics. Among existing fiber conductors, gallium-based liquid metals (LMs) featuring high conductivity, fluidity, and self-healing are excellent candidates for highly stretchable fibers with sensing, actuation, power generation, and interconnection functionalities. However, current LM fibers fabricated by direct injection or surface coating have a limitation in shape programmability. This hinders their applications in functional fibers with tunable electromechanical response and miniaturization. Here, we reported a simple and efficient method to create shape-programmable LM fibers using the phase transition of gallium. Gallium metal wires in the solid state can be easily shaped into a 3D helical structure, and the structure can be preserved after coating the wire with polyurethane and liquifying the metal. The 3D helical LM fiber offered enhanced stretchability with a high breaking strain of 1273% and showed invariable conductance over 283% strain. Moreover, we can reduce the fiber diameter by stretching the fiber during the solidification of polyurethane. We also demonstrated applications of the programmed fibers in self-powered strain sensing, heart rate monitoring, airflow, and humidity sensing. This work provided simple and facile ways toward functional LM fibers, which may facilitate the broad applications of LM fibers in e-skins, wearable computation, soft robots, and smart fabrics.

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Magnetic soft robots featuring untethered actuation and high mechanical compliance have promising applications ranging from bionics to biomedicine. However, their fixed magnetization profiles pose a challenge for adaptive shape transformation in unpredictable environments and dynamic tasks. Herein, a reprogrammable magnetic soft composite is reported by encapsulating magnetic neodymium–iron–boron microparticles with low melting alloy (LMA) and embedding them into the elastomer. Utilizing the phase transition of the LMA, the magnetic microparticles can be reoriented under an external magnetic field and they can be immobilized through LMA solidification, allowing the robot to obtain a new magnetization profile corresponding to its temporary shape. By changing the LMA composition, the robot with multiple programming temperatures can be fabricated and its local magnetization profiles can be selectively programmed in different temperature ranges. A bioinspired crawler with multimode locomotion, a reconfigurable robotic gripper capable of adaptable grasping, and reconfigurable electronic circuits are also demonstrated. This work may pave the way for the next‐generation magnetic soft robots and reconfigurable devices.