3D Printing-Enabled In-Situ Orientation of BaTi2O5 Nanorods in β-PVDF for High-Efficiency Piezoelectric Energy Harvesters.

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% β 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.