Finger flexion power generators made of piezoelectric lead zirconate titanate thin films on stainless steel foils

Abstract We have fabricated flexible piezoelectric energy harvesters (PEHs) composed of Pb(Zr,Ti)O3 (PZT) thin films on stainless steel foils and examined their power generation performance under a finger-bending motion for wearable applications. PZT thin films with a thickness of 3 μm were deposited on 30-μm-thick ferritic stainless steel (FSS) foils by RF magnetron sputtering, and the PEH elements were fabricated. Maximum effective output power of a single PZT thin-film PEH element reached 6 μW at 150 kΩ under the excitation of 2 m/s2 at the resonance frequency of 11 Hz and the piezoelectric coefficient e31, f of the PZT thin films on the FSS foils was found to be -6.3 C/m2. By connecting six PZT thin-film PEH elements, the output power of the stacked PEH increased to 13.4 μW at 300 kΩ. Because of small thickness of the PEH elements, the stacked PEH was flexible, and cracking or peeling of the PZT thin films did not occur during the continuous bending motion. The stacked PEH was embedded in gloves and light emitting diode (LED) lighting tests were conducted. By applying the finger-bending motions, we successfully turned the LED on intermittently using the generated electric power of the stacked PEH.