Solvent-assisted precipitation direct-write printing toward in-suit oriented β-phase polyvinylidene fluoride with tunable microarchitectures for energy harvesting and self-powered sensing

Additive manufacturing technology has attracted significant attention because it facilitates the one-step fabrication of complex structures for piezoelectric devices. In this study, a facile approach is proposed for manufacturing complex piezoelectric nanogenerators (PENGs) with an in-suit oriented β-phase of polyvinylidene fluoride (PVDF) based on solvent-assisted precipitation direct-write three-dimensional (3D) printing (SPDWP). This SPDWP has the ability to fabricate porous structures owing to the rapid nonsolvent-induced phase separation and controllable porosity of the fiber. In particular, the SPDWP based on ethanol precipitation increases the β-phase content of PVDF to 76.21%, representing a 1.5-fold improvement compared to that by the solvent casting technique. Moreover, the shape of the printed fiber—impacted by the printing parameters—significantly influences the piezoelectric performance. In particular, cylindrical fiber-based PENGs exhibit better piezoelectric performance than elliptical fiber-based PENGs, producing a higher voltage output of 11.3 V owing to the structural deformation, as confirmed by the simulation results. As expected, these printed PENGs can detect a variety of human movements, demonstrating that SPDWP is a novel method for fabricating 3D structural PENGs for self-powering microelectronic applications with the advantages of achieving geometric complexity, manufacturing simplicity, and low cost.