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This article reports a compact wideband piezoelectric vibration energy harvester consisting of three proof masses and an asymmetric M-shaped cantilever. The M-shaped beam comprises a main beam and two folded and dimension varied auxiliary beams interconnected through the proof mass at the end of the main cantilever. Such an arrangement constitutes a three degree-of-freedom vibrating body, which can tune the resonant frequencies of its first three orders close enough to obtain a utility wide bandwidth. The finite element simulation results and the experimental results are well matched. The operation bandwidth comprises three adjacent voltage peaks on account of the frequency interval shortening mechanism. The result shows that the proposed piezoelectric energy harvester could be efficient and adaptive in practical vibration circumstance based on multiple resonant modes.

Polyimide is used as a sacrificial material because of its low stress, its removable ability and its compatibility with standard micromachining processes. In this work, polyimide structures with inclined sidewalls are fabricated with a reactive ion etching process, where SiO2 is used as the hard-mask material. The structures can be further used as sacrificial layers in micro-electro-mechanical systems infrared (IR) sensors to support IR absorbers, to realize the thermal connections between the absorbers and the thermopiles, and to scale down the size of the sensors. As a result, IR sensors with low-residual-stress absorption, high structural stability, low heat loss and small dimensions can be achieved.