Electrohydrodynamic Pulling Consolidated High-Efficiency 3D Printing to Architect Unusual Self-Polarized β-PVDF Arrays for Advanced Piezoelectric Sensing.

Piezoelectric pressure sensors are important for applications in robotics, artificial intelligence, communication devices, etc. The hyperboloid is theoretically predicted to be an unusual 3D structure that allows concerted piezoelectric enhancement owing to its synergistic effects of geometrical stress confinement and stress concentration, but has not been experimentally fulfilled due to a lack of efficient architecting techniques. In this work, a 3D hyperboloidal arrayed self-polarized PVDF piezoelectric energy harvester (PEH) is successfully fabricated by incorporating electrohydrodynamic (EHD) pulling technology into fused deposition modeling (FDM) 3D printing. This strategy not only simplifies the layer-by-layer constructing procedure for arrays, but simultaneously realizes a self-polarized and high β-phase (92%) PVDF PEH in a single electric-pulling step, saving posttreatment such as poling and removing excessive additives. Such a PEH delivers a significantly enhanced piezoelectric potential which is around 8 times that of a 2D flat film sensor. Moreover, this PEH featuring excellent linearity within a wide pressure regime, enables the sensing of human activities in a relatively large force range, which is otherwise difficult for traditional film sensors to differentiate. This work demonstrates a potential roadmap to advanced piezoelectric sensors exploiting unusual 3D structures enabled by the unique EHD pulling coupled 3D printing technique.