Hybrid electromagnetic–triboelectric nanogenerator for harvesting vibration energy

We report a hybrid nanogenerator that includes a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) for scavenging mechanical energy. This nanogenerator operates in a hybrid mode using both the triboelectric and electromagnetic induction effects. Under a vibration frequency of 14 Hz, the fabricated TENG can deliver an open-circuit voltage of about 84 V, a short-circuit current of 43 μA, and a maximum power of 1.2 mW (the corresponding power per unit mass and volume are 1.82 mW/g and 3.4 W/m³, respectively) under a loading resistance of 2 MΩ, whereas the fabricated EMG can produce an opencircuit voltage of about 9.9 V, a short-circuit current of 7 mA, and a maximum power of 17.4 mW (the corresponding power per unit mass and volume are 0.53 mW/g and 3.7 W/m³, respectively) under a loading resistance of 2 kΩ. Impedance matching between the TENG and EMG can be achieved using a transformer to decrease the impedance of the TENG. Moreover, the energy produced by the hybrid nanogenerator can be stored in a home-made Li-ion battery. This research represents important progress toward practical applications of vibration energy generation for realizing self-charging power cells.