Weavable and Functional PVA/WPU/KNN Piezoceramic Composite Fiber for Flexible Textile Sensors

The flexibility of fiber-based materials offers significant advantages for developing wearable sensors. In this work, piezoceramic fibers were fabricated via a wet-spinning process using a two-component PVA/WPU system as the flexible matrix and lead-free sodium potassium niobate (KNN) particles as functional fillers. In cross-linking, spinning gel was used as the precursor solution in the spinning process, thereby overcoming the challenges of non-uniform dispersion of KNN piezoceramic and weak interfacial adhesion. By adjusting the mass ratio of KNN in the spinning gel, followed by crosslinking-induced gelation and coagulation bath treatment, three types of KNN-based composite fibers were successfully prepared. The morphology and structure of the fibers were systematically characterized, and finite element analysis (FEA) was also performed to analyze the potential distribution of the piezoelectric phase of fibers under mechanical loading. The obtained fibers exhibit excellent flexibility, good weaveability, and high sensitivity with stable real-time response under stimuli. Notably, the fabricated piezoceramic composite fibers achieve a high d33 value of 65.6 pC/N, generate an output voltage of up to 76.75 V under applied pressure, respond rapidly within 1.5 s, and show potential for integration into woven textile structures. The PVA/WPU/KNN piezoceramic composite fiber developed in this study demonstrates high sensitivity and excellent flexibility, indicating strong potential for applications in wearable and flexible textile sensors.