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.