A piezoelectric MEMS energy harvester (EH) with low resonant frequency and wide operation bandwidth was designed, microfabricated, and characterized. The MEMS piezoelectric energy harvesting cantilever consists of a silicon beam integrated with piezoelectric thin film (PZT) elements parallel-arranged on top and a silicon proof mass resulting in a low resonant frequency of 36 Hz. The whole chip was assembled onto a metal carrier with a limited spacer such that the operation frequency bandwidth can be widened to 17 Hz at the input acceleration of 1.0 g during frequency up-sweep. Load voltage and power generation for different numbers of PZT elements in series and in parallel connections were compared and discussed based on experimental and simulation results. Moreover, the EH device has a wideband and steadily increased power generation from 19.4 nW to 51.3 nW within the operation frequency bandwidth ranging from 30 Hz to 47 Hz at 1.0 g. Based on theoretical estimation, a potential output power of 0.53 μW could be harvested from low and irregular frequency vibrations by adjusting the PZT pattern and spacer thickness to achieve an optimal design.

We have developed a piezoelectric (PZT) microcantilever as an air flow sensor and a wind-driven energy harvester for a self-sustained flow-sensing microsystem. A flow sensing sensitivity of 0.9 mV/(m/s) is obtained. The output voltage and optimized power regarding to the load resistance of 100 kΩ are measured as 18.1 mV and 3.3 nW at flow velocity of 15.6 m/s, respectively. The corresponding power density is as large as 0.36 mW/cm³. The experimental results have elucidated the smart function of using PZT microcantilevers as flow-sensors and wind-driven energy harvesters simultaneously.