High-Performance Weavable Piezoelectret Fibers via Scalable In Situ Poling Melt-Spinning for Real-Time Knee Joint Rehabilitation Monitoring.

The scalable production of high-performance piezoelectric fibers remains a major hurdle for smart textile applications. Here, we report an in situ polarization strategy integrated into an industrially viable melt-spinning process for the continuous fabrication of piezoelectric polypropylene/barium titanate (PP/BTO) composite fibers. This approach simultaneously induces interfacial cavitation to form electret pore structures and accomplishes rapid dipole polarization under a high electric field during fiber drawing, eliminating the need for post-processing. The optimized PP/BTO fibers exhibit a high piezoelectric coefficient (d33) of 1.8 pC/N and a surface potential of -3.4 V, achieved with an ultralow poling time of 0.3 s. The fibers demonstrate exceptional flexibility and weavability, enabling their integration into large-scale textiles. As a proof-of-concept, a sensor-woven insole is constructed for real-time gait monitoring. Combined with machine learning, the system successfully recognizes different gait patterns with over 84% accuracy, showcasing significant potential for personalized rehabilitation diagnostics. This work provides an efficient and scalable pathway for manufacturing functional fibers, bridging the gap between laboratory innovation and industrial production.