Highly Conductive and Stretchable Photothermal CuSe Fiber for Wearable Electronics and Implantable Drug Release Systems

ABSTRACT Recently, fiber electronics have emerged as promising platforms for next‐generation wearable and biomedical systems because of their flexibility, light weight, and softness. Among them, photothermal fibers are particularly attractive for therapeutic applications because of their remote and localized heat generation. However, most existing photothermal fibers rely on near‐infrared (NIR)‐I‐responsive materials, which exhibit shallow tissue penetration and limited efficiency, thereby restricting their applicability in tissue implantation. In this study, a stretchable photothermal copper (II) selenide (CuSe) fiber was fabricated via a simple solution‐based synthesis. Owing to the uniformly embedded CuSe nanoplates within the polyurethane matrix, the fabricated CuSe fiber exhibits high electrical conductivity (3.419 S/cm), excellent stretchability (100% tensile strain), and stable heating up to 81.7°C under NIR‐II irradiation. When integrated into textiles, the fiber can function as both a reliable strain sensor (gauge factor = 28.88) and a wearable heater (photothermal conversion efficiency = 40.1%). In addition, an implantable NIR‐triggered drug release fiber was developed by coating the prepared CuSe fiber with a thermo‐responsive hydrogel, achieving photothermal‐triggered drug release and exhibiting therapeutic efficacy in mice with lipopolysaccharide‐induced sepsis. Overall, the developed NIR‐II‐responsive CuSe photothermal fiber provides a versatile and clinically relevant platform for next‐generation wearable and biomedical systems.