Lead-free piezoelectric MEMS energy harvesters of stainless steel cantilevers

We fabricated piezoelectric MEMS energy harvesters (EHs) of lead-free (K, Na)NbO
₃
(KNN) thin films on microfabricated stainless steel cantilevers. The 2.2-μm-thick KNN thin films were directly deposited by rf-magnetron sputtering onto the cantilevers, thereby we could simplify fabrication process of the EHs. Because of the strong fracture toughness of stainless steel, the thickness of the cantilevers can be as thin as 30 μm. We obtained large averaged output power of 1.6 μW at 393 Hz and 10 m/s
²
for the lead-free unimorph cantilever.