Enhanced Piezoelectric Performance of Composite Fibers Based on Lead-Free BCTZ Ceramics and P(VDF-TrFE) Piezopolymer for Self-Powered Wearable Sensors

Flexible piezoelectric energy harvesters (f-PEHs) have recently become popular alternative power sources for smart and wearable devices. For applications in self-powered wearable devices and biomedical applications, f-PEHs should exhibit high flexibility, nontoxicity, and excellent piezoelectricity. In this study, we developed high-efficiency ultra-f-PEHs based on electrospun piezoelectric composite fiber (PCF) membranes composed of lead-free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃(BCTZ) nanoparticles (NPs) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) fibers. In particular, post-treatments, including post-crystallization and an extra-poling process, were exploited to further enhance the piezoelectricity of the PCFs. The PCF membrane reached an output voltage of 36.5 V, a current signal of 1.09 μA, and an effective output power of 13.2 μW, which are higher compared to the previously reported PCF-based energy harvesters. Furthermore, an ultra-f-PEH consisting of aluminum electrodes, PCF membranes, and polydimethylsiloxane elastomers was proposed and successfully monitored tiny bio-signals, such as carotid pulses, vocalization, and articular bending motions. This study provides suggestions for applications in wearable and biomedical self-powered electronics using piezoelectric energy-harvesting systems.