Lead-Free (K,Na)NbO3 Impact-Induced-Oscillation Microenergy Harvester

We developed microenergy harvesters using impact-induced oscillation to scavenge electrical power from low frequency (<;200 Hz) and random environmental vibrations. The microharvesters comprised a (K,Na)NbO₃/Si composite cantilever and a cylindrical cavity to guide a metal ball to perpendicularly strike the cantilever. Through ball impact, oscillation of the cantilever was induced, generating electrical power at ambient vibration frequencies from 20 to 150 Hz. The contact time of ball impact was identified as a key parameter for power enhancement and was effectively tuned by adjusting the impact position on the triangular cantilever. The experimental output power when the impact position was at the base of the cantilever was 34.6 nW. This value is tenfold higher than that from conventional devices in which the ball strikes the tip of the cantilever.