Tunable broadband sliding-mode triboelectric energy harvester utilizing loaded string vibrations

The utilization of lateral sliding-mode triboelectric energy harvesters (LSTEH) for harvesting low-frequency ambient vibration energy holds immense promise but also presents considerable challenges. While most research has focused on material innovation, there is a noticeable gap in application-oriented studies on broadband triboelectric energy harvesters, especially those designed for vibration energy harvesting. This paper introduces a tunable broadband LSTEH using a loaded-string configuration. An electromechanical coupled model of the LSTEH is established, accounting for variable tension during string vibration and electrostatic forces between tribo-pairs. Experimental results align well with theoretical results, demonstrating both the broadband characteristics of the LSTEH and the accuracy of the model. Under an excitation of 4 mm in amplitude at 10 Hz, a single tribo-pair of the LSTEH achieves an output power of 41.1 μW. Even at a slightly lower frequency of 9.5 Hz with the same excitation amplitude, the output power remains at 17.6 μW. The LSTEH, with a mass ratio of 81.9, exhibits a peak frequency of 11.5 Hz and a bandwidth of 2.6 Hz at a 5 mm excitation amplitude. These results demonstrate the LSTEH’s ability to capture low-level vibrational energy while maintaining broadband characteristics. The resonant frequency of the LSTEH can be fine-tuned through both tension control and block mass modification. The proposed LSTEH is a cost-effective solution with great potential for harvesting energy from low-frequency vibrational resources.