Flexible and highly piezoelectric nanofibers with organic–inorganic coaxial structure for self-powered physiological multimodal sensing

The relatively low sensitivity of flexible piezoelectric nanogenerators (PENG) is the most urgent problem to be solved for their applications in internet of things and artificial intelligences. To improve the piezoelectricity of polymeric fibers without discount of flexibility, BaTiO3 nanowire (BTNW) with high aspect ratio is introduced into the piezoelectric P(VDF-TrFE) (denoted as PT) electrospun fibers to form coaxial composite nanofibers for improving the sensitivity towards external mechanical loads. To reinforce the organic–inorganic interfacial interaction for the improvement of the piezoelectric response, a nanolayer of polydopamine (PDA) is uniformly coated on the surface of BTNW (denoted as pBTNW) to form PT/pBTNW nanofibers. The introduction of 7 wt% pBTNW into the fibers significantly improves the polymeric β-phase conformation and mechanical properties, simultaneously, resulting in an optimal piezoelectric output of 18.2 V under an impact force of 5 N with excellent sensitivity of 4.3 V N−1. Through both theoretical simulation and experimental characterization, the PT/pBTNW-based PENG exhibits a higher electrical output than the equivalent nanoparticle-based PENG. The optimized PENG sensor can be used for self-powered and sensitive biomonitoring of physiological movements, finger identification and voice recognition. Overall, this work offers a reliable method for enhancing piezoelectricity of flexible polymeric nanofiber and designing high-performance PENG for wearable fabric-based sensors.