A cantilever-plucked and vibration-driven rotational energy harvester with high electric outputs

The ubiquitous and renewable vibration energy has been recognized as a promising energy source for the increasing number of low-power electronics, but its efficient harvesting is still an open issue. Here, an innovative vibration-to-rotation conversion mechanism (which we name ‘cantilever-plucked rotor’) is reported for converting ambient vibrations to uni-directional and high-speed rotation through a new plectrum design. Featuring a simple configuration and being attached on a cantilever beam, the proposed plectrum consists of a rigid part for spinning the rotor and a flexible part for reducing the frictional resistance acting on the rotor, enabling the plectrum to switch its effective stiffness automatically according to its motion with respect to the rotation of the rotor. An electromagnetic rotational energy harvester constructed with the cantilever-plucked rotor generates high output power of 4 mW under a harmonic vibration of 0.4 g (1 g = 9.8 m/s²) at 8.6 Hz, which is several times higher than that provided by a conventional electromagnetic energy harvester without the rotor. Under low-level vibrations (≤0.8 g), the constructed energy harvester can also generate sufficient electric energy for the continuous operation of some commercial electronics. This work demonstrates the promising potential of the cantilever-plucked rotational energy harvester in the efficient scavenging of ambient vibrations.