RESUMEN
Piezoelectric energy harvesters (PEHs) with a three-dimensional (3D) structure are arousing increasing interest because of the ability to efficiently convert mechanical energy into electricity catering for self-powered systems. Among them, 3D PEHs composed of 1-3-type piezoelectric composites which exploit one-dimensional (1D) piezoceramic fillers rather than conventional powders are particularly attractive. However, an issue involving the orientation of the 1D fillers to utilize the piezoelectric effect renders the 3D structural design for high-efficiency energy conversion more challenging. Herein, for the first time, we introduce the fused deposition modeling (FDM) 3D printing to the flexible construction of poly(vinylidene fluoride) (PVDF)-based 3D PEHs by incorporating 1D BaTi2O5 (BT2) nanorods as piezoelectric fillers. The shearing force generated by FDM successfully realizes the in situ uniform orientation of BT2 nanorods in the PVDF (98% ß crystals) matrix along the nozzle extrusion direction. Besides, by coupling 3D printing with the appealing piezoelectric anisotropy feature of BT2 nanorods, the 3D PEH is able to generate different piezoelectric responses to the same applied external force from X, Y, and Z directions. Furthermore, an optimized 3D conical array structure is constructed to amplify the effective deformation of the PEH to enhance its piezoelectric output. As expected, customized PEH can continuously power commercial electronic devices and monitor various human motions, indicating 3D printing as a multifunctional strategy to fabricate 3D PEHs with 1-3-type piezoelectric composite materials for self-powering microelectronic applications.
RESUMEN
Three-dimensional (3D) printing technologies have unparalleled advantages in constructing piezoelectric devices with three-dimensional structures, which are conducive to improving the efficiency of energy harvesting. Among them, fused deposition modeling (FDM) is the most widely used thanks to its low cost and wide range of molding materials. However, as the best piezoelectric polymer, a high electroactive ß-phase poly(vinylidene fluoride) (PVDF) piezoelectric device cannot be directly obtained by FDM printing because the ß-crystal is unstable at the molten state. Herein, we develop for the first time ionic liquid (IL)-assisted FDM for direct printing of ß-PVDF piezoelectric devices. An IL can induce and maintain ß crystals during melt extrusion and FDM printing, ensuring that the ß-crystal in the printed PVDF device is as high as 98.3%, which is the highest in 3D-printed PVDF as far as we know. Furthermore, the shearing force provided by the FDM facilitates the directional arrangement of the dipoles, resulting in the printed PVDF device having self-polarization characteristics without poling. Finally, the piezoelectric output voltage of the 3D-printed PVDF device is 4.7 times that of the flat PVDF device, and its area current density (17.5 nA cm-2) is more than that of the reported 3D-printed PVDF piezoelectric device in the literature by two orders of magnitude. The one-step 3D printing strategy proposed in this paper can realize the rapid preparation of complex-shaped and lightweight self-polarized ß-PVDF-based piezoelectric devices for energy harvesting.