Toward Optimizing Resonance for Enhanced Triboelectrification of Oscillating Triboelectric Nanogenerators

Mechanical resonant designs for oscillating triboelectric nanogenerators (O-TENGs) are effective for boosting output power at a resonant frequency, but there remains room for optimizing output performance because of the various equivalent resonant designs at the same resonant frequency. Here, we report an optimized resonant design for enhancing the output performance of O-TENGs. We theoretically design O-TENGs with different masses and spring stiffnesses at equal resonant frequencies. The triboelectric outputs of the O-TENGs improve with increasing mass and spring stiffness at the resonant frequency. To understand the enhancing mechanism, the dynamic properties such as velocity, acceleration, and contact load are analyzed. We find that increasing the contact load enhances the triboelectric outputs. In addition, we confirm that increasing the gap distance enhances the triboelectric output, but also that there is an optimal gap distance due to the vibration mode of the O-TENG. Finally, we design a tandem O-TENG with a ground system to harvest broadband vibration energy and to synergistically improve the triboelectric performance. We successfully demonstrate an overall four-fold improvement in the output voltage from 38 to 150 V. We expect that our results can provide critical design rules for effectively boosting and optimizing the output power of O-TENGs.