Boosting Sensitivity of Piezoelectric Sensors by Electrohydrodynamic Pulling Promoted In Situ Foaming

Polymer-based piezoelectric sensors are gaining widespread attraction for wearable sensing applications due to their light weight, flexibility, and self-powered performance. Wherein high response sensitivity and good linearity are essential for piezoelectric sensors. However, conventional piezoelectric sensors are limited in their ability to exploit space fully to generate adequate strain, leading to a relatively low piezoelectric output and insufficient sensitivity under a broad stress linearity range. Herein, an electrohydrodynamic (EHD) pulling-promoted in situ foaming technology is proposed to significantly enhance the sensitivity of piezoelectric sensors. The results indicate that the EHD pulling facilitates in situ pore formation, thus enhancing the piezoelectric output voltage without disturbing the material's initial crystal structure. Furthermore, the synergistic integration of microcellular pores and a 3D macroporous architecture enhance electromechanical conversion efficiency through optimized stress distribution and increased effective strain accumulation. As expected, the porous hyperboloidal arrayed PVDF/IL/AC-2 sensor exhibits resultant piezoelectric performance (11 V and 160 nA), with an open-circuit voltage 2.8 times that of nonfoamed counterparts. Concurrently, this piezoelectric sensor boasts an excellent sensitivity of 640 mV/N under a load force between 2.0 and 17.5 N, surpassing most PVDF-based piezoelectric sensors. These performance metrics enable effective implementation in human motion detection applications, particularly in joint articulation monitoring and gait analysis scenarios. The innovative multistage PVDF architecture offers substantial promise for intelligent sensing applications.