Lead-free (K, Na)NbO3 based impact type energy harvesters integrated with a cylindrical cavity for metal ball

In this study, we developed lead-free (K, Na)NbO₃ (KNN) based energy harvesters using impact of the metal ball. A metal ball was put in a built-in cylindrical cavity to perpendicularly impact the KNN/Si cantilever. Due to this impact, free oscillation of the cantilever was induced. This device can operate at low and wide frequency range of 20-190 Hz, and is suitable for the energy harvesting from the environmental vibration. We evaluated the influence of the impact point on the cantilever for the power generation. As a result, the harvested power increased up to 15-fold when the impact position moved from tip to base of the cantilever. The maximum power of 44 nW was obtained with a 2.5 mm length cantilever when the shaking frequency, acceleration and load resistance were 190 Hz, 39 m/s² (4g) and 7.3 KΩ, respectively.