Hierarchically Architected Polyvinylidene Fluoride Piezoelectric Foam for Boosted Mechanical Energy Harvesting and Self-Powered Sensor

With the rapid development of wearable electronics, piezoelectric materials have received great attention owing to their potential solution to the portable power source. To enhance the output capability and broaden the application, it is highly desired for the design of piezoelectric materials with a three-dimensional and porous structure to facilitate strain accumulation. Herein, enlightened by hierarchical structures in nature, a hierarchically nested network was constructed in polyvinylidene fluoride (PVDF) foam via solid-state shear milling and salt-leaching technology. The as-prepared foam exhibited two hierarchical levels of pores with diameters of 20∼50 μm and 0.3∼4 μm, by which the porosity and flexibility were significantly enhanced, while the highest piezoelectric output reached 11.84 V and 217.78 nA. As a proof-of-concept, the PVDF piezoelectric foam can also be used to monitor human movement toward the different magnitude of strain and frequency, and simultaneously collect energy in a multidimensional stress field for energy harvesting. This work provides a simple and convenient design idea for the preparation of energy harvesters, which have great application potential as a mechanical energy harvester or self-powered sensor in wearable electronic devices.