Oriented β-phase and porous architecture synergistically boost piezoelectricity of poly(vinylidene fluoride) films for wearable electronics

Melt stretching and ZnO nanofillers induce highly oriented β-phase with an 81.7% fraction. • Flow-driven ZnO interconnection constructs acid-etching channels for anisotropic pore formation. • Oriented β-phase and porous architecture synergistically boost piezoelectric output. • Piezoelectric film devices enable wearable sensing and CNN-assisted information transmission. Oriented β-phase crystallites and well-defined porous structures are two well-established routes to boost PVDF piezoelectricity, yet integrating both in a single material remains an unsolved challenge. Here, we report a film processing strategy by combining ZnO incorporation, irradiation crosslinking, melt stretching, and acid etching to address this issue. ZnO nanoparticles play a dual role, serving as both a promoter to enhance flow-induced β-phase formation and a sacrificial template for pore generation. The synergistic effects of high ZnO loading (60 wt%), slight chain crosslinking, and strong melt stretching (20×) yield highly oriented β-phase with a fraction as high as 81.7%. Meanwhile, flow-induced redispersion of ZnO aggregates forms an interconnected nanofiller network, enabling complete ZnO removal upon acid etching to generate anisotropic pores. The resulting porous architecture, together with the oriented β-phase, enhances piezoelectric performance through three synergistic mechanisms: the intrinsic piezoelectricity of the β-phase, reduced dielectric permittivity, and the piezoelectret effect of the pores. The optimized film achieves a high piezoelectric coefficient ( d 33 ) of 69.6 pC/N and a figure of merit of 4.6 × 10 −11  m 2 /N, with robust mechanical properties. The corresponding piezoelectric device exhibits a broad force-response range, high sensitivity to weak stimuli, and excellent cyclic stability. Flexible sensors based on these films can monitor human motion and physiological signals, and integration with a two-dimensional convolutional neural network enables Morse-code-based transmission with 98.4% accuracy. This work offers a scalable melt-processing route for high-performance porous PVDF piezoelectric films toward flexible wearable electronics and self-powered sensing systems. Download: Download high-res image (241KB) Download: Download full-size image