Significant piezoelectric and energy harvesting enhancement of poly(vinylidene fluoride)/polypeptide fiber composites prepared through near-field electrospinning

In this study we applied near-field electrospinning (NFES) to prepare ordered poly(vinylidene fluoride) (PVDF)/poly(g-methyl L-glutamate) (PMLG) composite fibers displaying enhanced piezoelectricity. Using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC), we analyzed the miscibility, specific interactions, and secondary structures of the PVDF/PMLG composites. The NFES process improved the piezoelectric properties of the PMLG/PVDF composites, resulting in better orientation of their dipoles, a high ultimate stress (27.47 MPa), and a high Young's modulus (2.77 GPa), as determined through micro-tensile testing. After patterning PVDF/PMLG piezoelectric composite fibers onto a poly(ethylene terephthalate)-based structure with parallel electrodes, we obtained a flexible PVDF/PMLG energy harvester that could capture ambient energy with a maximum peak voltage of 0.08 V, a power of 637.81 pW, and the energy conversion efficiency is 3.3%. The electro-mechanical energy conversion efficiency of this PVDF/PMLG energy harvester was up to three times higher than those of pristine individual PVDF and PMLG energy harvesters. Such PMLG/PVDF piezoelectric composite fibers exhibiting good piezoelectricity and good mechanical properties might have applicability in several fields, including biomedical engineering, green energy, wearable sensors, and energy harvesting.