A fully encapsulated piezoelectric-triboelectric hybrid nanogenerator for energy harvesting from biomechanical and environmental sources

In this paper, a hybrid nanogenerator with concurrently harvested piezoelectric and triboelectric mechanisms, called a fully encapsulated piezoelectric-triboelectric hybrid nanogenerator (PTHG), is demonstrated. In the construction of piezoelectric nanogenerator (PENG), an in-situ poling near-field electrospinning (NFES) was utilized to direct-write piezoelectric polymeric nano/micro fibers (NMFs) polyvinylidene fluoride (PVDF) as the functional layer of piezoelectric nanogenerators. On the other hand, the nano-textured functional layer of triboelectric nanogenerators (TENGs) is also concurrently combined with PENG. This hybridized nanogenerator was demonstrated to simultaneously harvest piezoelectric and triboelectric output such that the superimposed peak output voltage /current signals of ~130 V/4 µA at 2 Hz, which can be translated to the area power density of 8.34 mW/m². Individually measured TENG under a hand-induced strain 0.2 and 2 Hz actuation, the output voltage/current peak is measured about 110 V/2.8 µA, while the PENG counterpart shows the the output voltage/current peak is about 18 V/0.6 µA. In addition, the proposed PTHG can harvest sustainable energy sources such as rain water with the output maximum voltage reaches ~20 V and area power density ~0.981 mW/m² for dropping rate of 10 ml/s. This research shows the substantial improvement in the synergy of nano-textured triboelectric and piezoelectric functional layers. The practical application of the self-powered system can be ubiquitously implemented in the sustainable energy sources and future industry 4.0 scenarios to provide the stand alone energy sources of IoT sensors.