Characteristic of solid-ferrofluid triboelectric nanogenerator for ultra-low-frequency vibration energy harvesting

Durability problems caused by friction loss have restricted the development of a solid-solid triboelectric nanogenerator, which has provided an opportunity for the solid-liquid triboelectric nanogenerator. Ferrofluid has been used in the solid-liquid triboelectric nanogenerators due to its liquid and magnetization properties. In this study, we propose a solid-ferrofluid triboelectric nanogenerator (SF-TENG) for ultra-low-frequency vibration energy harvesting. This SF-TENG can harvest swing vibrations using friction electrification between the polytetrafluoroethylene shell and ferrofluid. To increase the moving speeds of charges, we applied a magnetic field to the SF-TENG to raise the flow velocity of the ferrofluid. The volume of ferrofluid and the magnetic field intensity applied were optimized to enhance the performance of the SF-TENG. We then characterized the SF-TENG by applying frequency swing vibrations of 0.1–0.5 Hz. When the frequency of the input swing was 0.5 Hz, the peak-to-peak value of the open-circuit voltages was 0.98 V, and the maximum instantaneous current was 1.05 nA. In addition, the output power was approximately 1.03 nW, and the power density was 0.0426 mW/m3. The peak output power of the SF-TENG parallel array reached 18.2 nW at the 700 MΩ load resistance. And the capacitor with capacity of 1 μF can be charged to 1.5 V in 150 s.