Thermoplastic and Recyclable EGaIn-SEBS/WPU Fibers via Wet Spinning with Ultrahigh Stretchability and High Electrical Conductivity

Highly stretchable and electrically conductive fibers are critical for flexible electronic devices. In this study, we developed EGaIn-SEBS/WPU fibers (ESWFs) via a scalable wet-spinning process, where eutectic gallium–indium (EGaIn) particles were composited with styrene-ethylene-butylene-styrene (SEBS) and encapsulated by waterborne polyurethane (WPU) to integrate high conductivity, ultrahigh stretchability, and thermoplastic reconfigurability─addressing the inherent trade-off between conductivity and stretchability in wet-spun liquid metal fibers. Continuous ESWFs (length >20 m) were fabricated, with mechanical sintering enabling a maximum conductivity of 2.6 × 105 S/m at 95 wt % EGaIn content, and the fibers exhibited a hyperelastic stretching range of 0–780% while maintaining stable performance over 4000 cycles of 200% stretching; leveraging the thermoplasticity of the WPU encapsulation layer, ESWFs could be molded into a helical structure at ∼160 °C, extending the sensing range to 0–3300% (Q = criticalstrainsrelativeresistancechange = 8920) for ultrastretchable electrode applications, and dual ESWFs fabricated via the same wet-spinning process could be twisted into capacitive sensors with tunable sensitivity. Notably, ESWFs showed excellent recyclability with an EGaIn recovery rate of 94.74% by dissolving the polymer matrix, highlighting the rational design of the EGaIn-SEBS/WPU material system and the versatility of the wet-spinning process, which delivers fibers with integrated core properties that hold substantial promise for the scalable fabrication of flexible electronics.