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J. Iannacci, G. Sordo, E. Serra, U. Schmid:
"The MEMS four‑leaf clover wideband vibration energy harvesting device: design concept and experimental verification";
Microsystem Technologies - Micro- and Nanosystems - Information Storage and Processing Systems, 22 (2016), S. 1865 - 1881.

In this contribution, we discuss a novel
design concept of a high-performance wideband MEMS
vibration energy harvester (EH), named four-leaf clover
(FLC EH-MEMS) after its circular shape featuring four
petal-like mass-spring systems. The goal is to enable
multiple resonant modes in the typical range of vibrations
scattered in the environment (i.e., up to 4-5 kHz).
This boosts the FLC conversion capability from mechanical
into electrical energy exploiting the piezoelectric
effect, thus overcoming the common limitation of cantilever-
like EHs that exhibit good performance only in
a very narrow band of vibration (i.e., fundamental resonant
mode). The FLC concept is first discussed framing
it into the current state of the art, highlighting its
strengths. Then, after a brief theoretical introduction
on mechanical resonators, the FLC EH-MEMS device
is described in details. Finite Element Method (FEM)
analyses are conducted in the ANSYS Workbench^TM
framework. A suitable 3D model is built up to perform
modal simulations, aimed to identify mechanical resonant
modes, as well as harmonic analyses, devoted to
study the mechanical and electrical behaviour of the
FLC EH-MEMS (coupled field analysis). The work
reports on experimental activities, as well. Physical samples
of the FLC EH-MEMS device are fabricated within a technology platform that combines surface and bulk
micromachining. Thereafter, specimens are tested both
with a laser doppler vibrometer measurement setup as
well as with a dedicated shaker-based setup, and the
results are compared with simulations for validation
purposes. In conclusion, the FLC EH-MEMS exhibits a
large number of resonant modes scattered in the tested
range of vibrations (up to 15 kHz) already starting from
frequencies as low as 200 Hz, and expected levels of
converted power better than 10 μW.

In this contribution, we discuss a novel
design concept of a high-performance wideband MEMS
vibration energy harvester (EH), named four-leaf clover
(FLC EH-MEMS) after its circular shape featuring four
petal-like mass-spring systems. The goal is to enable
multiple resonant modes in the typical range of vibrations
scattered in the environment (i.e., up to 4-5 kHz).
This boosts the FLC conversion capability from mechanical
into electrical energy exploiting the piezoelectric
effect, thus overcoming the common limitation of cantilever-
like EHs that exhibit good performance only in
a very narrow band of vibration (i.e., fundamental resonant
mode). The FLC concept is first discussed framing
it into the current state of the art, highlighting its
strengths. Then, after a brief theoretical introduction
on mechanical resonators, the FLC EH-MEMS device
is described in details. Finite Element Method (FEM)
analyses are conducted in the ANSYS Workbench^TM
framework. A suitable 3D model is built up to perform
modal simulations, aimed to identify mechanical resonant
modes, as well as harmonic analyses, devoted to
study the mechanical and electrical behaviour of the
FLC EH-MEMS (coupled field analysis). The work
reports on experimental activities, as well. Physical samples
of the FLC EH-MEMS device are fabricated within a technology platform that combines surface and bulk
micromachining. Thereafter, specimens are tested both
with a laser doppler vibrometer measurement setup as
well as with a dedicated shaker-based setup, and the
results are compared with simulations for validation
purposes. In conclusion, the FLC EH-MEMS exhibits a
large number of resonant modes scattered in the tested
range of vibrations (up to 15 kHz) already starting from
frequencies as low as 200 Hz, and expected levels of
converted power better than 10 μW.

http://dx.doi.org/10.1007/s00542-016-2886-3