Robust superhydrophobic wearable piezoelectric nanogenerators for self-powered body motion sensors

Self-powered wearable sensors have attracted extensive attention in tactile sensing, motion-detecting, and biomedical signal monitoring. The practical application of these devices, however, requires not only their high sensitivity, flexibility, and breathability, but also mechanical durability and long-term resistance to humidity, liquid, and bacteria. Herein, a robust superhydrophobic antibacterial self-powered piezoelectric nanogenerator (PENG) sensor is reported. The PENG sensor is comprised of flexible electrospun poly(vinylidene fluoride-co-trifluoroethylene) piezoelectric nanofiber membrane with spray-coated interdigitated carbon nanotube electrodes, which were subsequently encapsulated by a crosslinked conformal hydrophobic nanocoating wrapping around each individual fiber through initiated chemical vapor deposition (iCVD). The obtained sensor could accurately monitor various human behaviors such as breathing and different motions. The iCVD nanocoating provides excellent protection to the sensor, imparting self-cleaning, superhydrophobicity, and more than 90% anti-fouling rate against bacteria. As a result, the sensor shows reliable and durable sensing performance under harsh environments such as high humidity, chemical exposure, and mechanical impact. Finally, owing to its extraordinary long-term durability and stability, the PENG sensor was successfully integrated into shoe insoles to realize human gait monitoring.