Architecting Three-Dimensional Porous Energy Harvesters with Bamboo-Like Filaments for Enhanced Piezoelectric Performance

Three-dimensional (3D) poly(vinylidene fluoride) (PVDF)-based piezoelectric energy harvesters (PEHs) offer exceptional electromechanical conversion capabilities due to their flexible structures and customizable designs. However, how to design and construct such structures with enhanced strain for a higher piezoelectric output remains a complex challenge. This study presents a novel approach by combining the versatility of 3D printing with solvent exchange to create a unique 3D porous bamboo-structured PVDF/MXene PEH, allowing for a tailored hollow structure by adjusting the temperature and solvent concentration. This flexible design and construction of the macro- and micro-3D structures enables a synergistic amplification of stress-strain, hence a significant enhancement of the overall electromechanical conversion efficiency of the PEH. Additionally, the incorporation of MXene, with its abundant functional groups, achieves a high β-crystal content (92.6%) in the PVDF-based PEH. This coupling effect contributes to a piezoelectric output of 47 V and maximum sensitivity of 0.727 V/kPa, surpassing most PVDF-based sensors reported to date. Notably, the 3D PEH demonstrates its potential as a self-powered pressure sensor for monitoring human motions across varying amplitudes. This work unveils a universal strategy for harnessing 3D PEHs with high electromechanical conversion efficiency, paving the way for various applications in the fields of smart sensing and energy harvesting.