Porosity manipulation to boost piezoelectric output via supercritical carbon dioxide foaming and surface modification

Abstract

Flexible piezoelectric devices for energy harvesting have long been attractive in the field of collecting distributed mechanical sources. However, the piezoelectric performance of the state-of-art piezoelectric devices were still limited by poor strain accumulation effect of traditional film or fiber based piezoelectric energy harvesters. Herein, flexible poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF)/barium titanate (BT) three-dimensional (3D) porous composite foam with perfected interface and controlled porosity was prepared via supercritical carbon dioxide (scCO2) foaming technology and surface modification. By manipulating foaming conditions, PVDF foams with uniform cellular structures were successfully obtained. The further introduction of surface coating of polydopamine (PDA) onto BT optimized distribution of BT and foaming behaviors of the composites, and thus by synergetic effect of BT and modulated 3D porous structure, the piezoelectric output was finally improved to ∼12.5 V and ∼150 nA with a peak output power density of ∼0.15 μW/cm2, which was ∼25 times of that of flat-film. Taking advantages of the comprehensive electromechanical performance, the integrated piezoelectric devices can be applied to collect micro sources from use of keyboard and power micro-electronics. Our work provides a simple microstructure design strategy for modulating the porosity to boost the piezoelectric output.

Keywords

• Piezoelectric
• Porous structure
• Poly(vinylidene fluoride-co-hexafluoropropylene)
• Barium titanate