Supercritical Fluid Foaming of Self-Polarized β-PVDF Piezoelectric Foam with Tailored Cells for Advanced Energy Harvesting
Xingang Liu, Xi Li, Xingneng Wei, Junyu Chen, Yijun Li, Chuhong Zhang
Abstract
Porous poly(vinylidene fluoride) (PVDF) attracts considerable attention for mechanical energy harvesting and self-powered systems owing to its exceptional electromechanical coupling capabilities. Supercritical carbon dioxide foaming (SCF) that features solvent-free and green nature is one of the most preferable approaches to construct controllably porous polymers. Nonetheless, the electroactive β-phase of PVDF remains elusive during SCF due to its instability under an elevated temperature. Herein, we pioneer the use of ionic liquid (IL)-assisted SCF for the fabrication of self-polarized β-PVDF piezoelectric foam with tailored cells. IL incorporation not only facilitates CO 2 infusion but also catalyzes the formation and preservation of β-phase crystals throughout the SCF process, culminating in a PVDF foam with an exceptionally high β-phase content (98%). Furthermore, the constructed honeycomb-like pore can effectively absorb external forces and significantly amplify the compressive strain, substantially enhancing the piezoelectric output of the PVDF foam. Impressively, PVDF foam with circumferential pore delivers a maximum piezoelectric output of 19.1 V, setting a new benchmark for SCF fabricated PVDF-based foam PEH. This advanced piezoelectric PVDF foam demonstrates significant potential as a flexible sensor for real-time monitoring of human foot pressure, highlighting its utility in adaptive sensing applications.