A liquid-electrode ultra-stretchable monolithic illuminating fiber

Fiber-based light-emitting devices hold promise for next-generation wearable electronics and human-machine interfaces. However, optoelectronic stability under extreme deformation remains challenging due to mechanical incompatibility at heterogeneous solid-solid interfaces and the difficulty of reconciling conflicting functionalities within fiber electrodes. Here, a liquid-electrode ultra-stretchable monolithic illuminating (LUMI) fiber is presented to address these interfacial limitations. Fabricated via scalable thermal drawing, the LUMI fiber consists of a central liquid metal core and symmetric ionic liquid channels embedded in a unified thermoplastic elastomer matrix. This architecture forms adaptive liquid-solid interfaces, ensuring robust electrical contact and maintaining uniform radial electric fields during dynamic deformation. As a result, the LUMI fiber exhibits excellent omnidirectional luminescence uniformity, sustaining up to 500% tensile strain while preserving stable luminance over 15,000 stretching cycles. Its versatility is further demonstrated by seamless integration into complex textile patterns and adaptability to dynamic, irregular surfaces. Overall, this work provides a comprehensive strategy for developing durable, scalable, and high-performance interactive fibers, advancing the frontiers of stretchable displays and electronic skins.