An ultra-thin piezoelectric nanogenerator with breathable, superhydrophobic, and antibacterial properties for human motion monitoring

Piezoelectric nanogenerators (PENGs) are promising for harvesting renewable and abundant mechanical energy with high efficiency. Up to now, published research studies have mainly focused on increasing the sensitivity and output of PENGs. The technical challenges in relation to practicability, comfort, and antibacterial performance, which are critically important for wearable applications, have not been well addressed. To overcome the limitations, we developed an all-nanofiber PENG (ANF-PENG) with a sandwich structure, in which the middle poly(vinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP))/ZnO electrospun nanofibers serve as the piezoelectric layer, and the above and below electrostatic direct-writing P(VDF-HFP)/ZnO nanofiber membranes with a 110 nm Ag layer on one side that was plated by vacuum coating technique serve as the electrode layer. As the ANF-PENG only has 91 μm thick and does not need further encapsulating, it has a high air permeability of 24.97 mm/s. ZnO nanoparticles in ANF-PENG not only improve the piezoelectric output, but also have antibacterial function (over 98%). The multi-functional ANF-PENG demonstrates good sensitivity to human motion and can harvest mechanical energy, indicating great potential applications in flexible self-powered electronic wearables and body health monitoring.