Core-sheath PVDF hollow porous fibers via coaxial wet spinning for energy harvesting

Flexible piezoelectric nanogenerators (PENGs), as a promising sustainable power source in smart electronics, have attracted much attention for their potential applications in the Internet of Things. In this paper, poly(vinylidene fluoride) (PVDF) fibers with core-sheath hollow porous structure were prepared by coaxial wet spinning process, serving as the dielectric layer, which were perfused internally by liquid metal (LM) as the inner electrode layer and wrapped outside by copper-silver nanoparticles (Cu@AgNP) as the outer electrode layer, thus constructing high-performance PVDF/LM/Cu@AgNP composite fibers. The composite PVDF fibers have a layered pore structure and arbitrarily deformable LM electrodes, which can significantly reduce the effective electric constant and thus enhance the piezoelectric properties. The results reveal that PVDF/LM/Cu@AgNP-PENG yields an optimal voltage output of 410 mV, providing a clear advantage over PENG by using alternative fibers. Moreover, the PVDF/LM/Cu@AgNP-PENG shows an excellent charging capability for energy storage devices, being able to charge 1 μF capacitors to 10 V within 30 s and directly power commercial LEDs. This study demonstrates the significant potential for utilizing composite PVDF piezoelectric fibers in flexible wearable electronic devices.