Airflow energy harvester of piezoelectric thin-film bimorph using self-excited vibration

•Small-scale airflow energy harvesters piezoelectric thin films are developed.•Piezoelectric bimorphs are fabricated from PZT thin films, which are directly deposited on both sides of stainless-steel foils.•Because of the high flexibility of PZT thin-film bimorphs, large output power (∼53 μW) can be generated byself-excited vibration under continuous airflow.

The airflow energy harvesters (AFEHs) of piezoelectric Pb(Zr,Ti)O3 (PZT) thin films were developed. Electric power was generated by self-excited vibration of the piezoelectric bimorph cantilevers induced by a continuous airflow. To enhance the vibration in low wind speed, we used very thin stainless-steel (SS) foils with thickness of 20 μm as base substrates, and the PZT thin films were deposited on both surface of SS foils by radio-frequency (rf) magnetron sputtering. When the angle of attack (AOA) was 20° and above, stable self-excited vibration was generated at wind speeds larger than 4.5 m/s. When the wind speed was 8 m/s, the maximum output power reached 36.4 μW at the AOA of 20°. From the evaluation of the thickness effect of the base cantilevers, it was confirmed that the thinner substrate reduced not only cut-in wind speed but also maximum output voltage.