Electric-Assisted Coaxial Wet Spinning of Radially Oriented Boron Nitride Nanosheet-Based Composite Fiber with Highly Enhanced Piezoelectricity

Piezoelectric filler-based composite fiber sensors have emerged as promising candidates for wearable textiles due to their self-powered capability and excellent sensing performance. However, current spinning fabrication methods face significant challenges in achieving uniform distribution and optimal orientation of piezoelectric fillers within polymer matrices, which limits their sensing performance. To address these issues, an innovative electric-assisted coaxial wet spinning method is developed to fabricate piezoelectric composite fiber (denoted as P-B fiber), which was composed of boron nitride nanosheets (BNNSs) as piezoelectric fillers and polyvinylidene fluoride (PVDF) as a piezoelectric polymer matrix. The radial electric field applied during spinning promotes the radial orientation of BNNSs, leading to enhanced stress transfer efficiency and, as a result, improved piezoelectricity. Moreover, the radial electric field enables the simultaneous in-situ polarization of BNNSs and PVDF during spinning process, further improving the piezoelectric performance. As a result, the P-B fiber exhibits an exceptional piezoelectric sensitivity of (186.4 ± 1.1) mV/N, approximately sixfold higher than that of fibers produced without electric field assistance. Accordingly, the P-B fiber demonstrates remarkable capability in detecting tiny mechanical loads, such as pulse waves and respiration, making it particularly suitable for wearable physiological monitoring textiles, providing a promising strategy for developing high-performance piezoelectric fiber sensors.