Stretchable, Self-Healing, and Highly Stable Conductive Fiber Based on Bio-Based PLA-Diol for Wearable Biosensing

The rapid advancement of smart wearable textile biosensors has elevated demands for functional materials, particularly regarding their mechanical and electrical properties, environmental sustainability, cost-effectiveness, and scalability. Herein, we present a novel bio-based poly(lactic acid diol) (PLA-diol)/multiwalled carbon nanotube (MWCNT) nanoconductive fluid (PC-NCF). By utilization of PLA-diol as the dispersion medium, this fluid not only reduces the environmental impact of conventional solvent-based systems but also enhances the uniformity and stability of the conductive network. The PC-NCF exhibits liquid-metal-like self-healing capabilities, exceptional ductility, plasticity, and low-temperature processability. To further advance applications, a stretchable conductive fiber (PPCF) was fabricated via coaxial wet spinning featuring a core-shell architecture: the PC-NCF core is encapsulated by a PLA-diol-based polyurethane (PLAU) shell. Incorporating PLA-diol as a soft segment in PLAU improves the degradability and environmental compatibility while regulating the microphase separation between soft and hard segments, thereby enhancing flexibility and resilience. The PPCF's unique design, enabled by self-healing interfaces and dynamic stress transfer, ensures continuous electrical conductivity (3 S/m at 200% strain) and robust cyclic stability (8000 cycles at 100% strain), achieving a balance between mechanical performance and conductivity. Notably, the gauge factor (GF) reaches 10.62 in the 200-300% strain range. Additionally, the PPCF demonstrates rare attributes, including cryogenic adaptability (-10 °C) and closed-loop recyclability. In dynamic physiological signal monitoring, the fiber adheres conformally to the skin, enabling real-time capture of both large and subtle electrophysiological changes. These results highlight the PPCF's potential as a high-performance flexible bioelectronic sensor for next-generation wearable textiles.