Stretchable and leakage-free coaxial liquid metal fibers for wearable and neural bioelectronics

Stretchable conductive fibers are key components for next-generation wearable electronics. Gallium-based liquid metals (LMs), with high conductivity and deformability, are promising candidates but suffer from surface tension and leakage issues. Here, we report a coaxial spinning strategy to fabricate highly stretchable, leakage-free core–sheath fibers. Liquid metal particles embedded in a polydimethylsiloxane (PDMS) core are encapsulated by a Dragon Skin elastomer sheath, effectively restricting LM mobility and preventing leakage under large deformation. Under strain, deformation-induced structural evolution of LM particles is associated with conductive-pathway reconstruction, allowing the fibers to maintain electrical conduction at elongations above 600%. Based on these fibers, double-helical capacitive sensors were constructed, showing linear, tunable, and low-hysteresis strain responses for reliable posture monitoring. Furthermore, through interfacial engineering using silver paste and hydrogel, the fibers were further developed into wearable and acutely implantable bioelectrodes. These electrodes enabled on-skin EMG acquisition comparable to commercial electrodes and supported stable acute neural recording/stimulation in vivo, while avoiding direct LM exposure at the biointerface. Overall, these core–sheath LM fibers offer a versatile, leakage-free platform for wearable and bioelectronic applications, bridging soft materials with functional electronic systems.