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M. Dorfmeister, B. Kössl, M. Schneider, G. Pfusterschmied, U. Schmid:
"Switching performance of bistable membranes activated with integrated piezoelectric thin film transducers";
Journal of Micromechanics and Microengineering, 29 (2019), 1 - 11.

In this paper we report on the fabrication of bistable micro electromechanical systems (MEMS)
membranes, which have diameters in the range of 600-800 μm, a total thickness of 3.13 μm
and feature integrated low power piezoelectric transducers based on aluminium nitride. To
estimate the impact of the membrane asymmetry due to the integrated piezoelectric transducers,
an asymmetric constant in the potential energy calculation of the bistable system is introduced,
thus enabling a proper theoretical prediction of the membrane behaviour. To switch between
the two bistable ground states, rectangular pulses with frequencies in the range of 50-100 kHz
and a peak-to-peak voltage of 30 Vpp are applied. Two different actuation schemes were
investigated, whereas one shows positive and the other negative pulse amplitudes. With a Laser-
Doppler Vibrometer the velocity of the membranes during the bistable switching process is
measured and integrated over time to calculate the membrane displacement in the centre. FFT
(fast Fourier transform) spectra of an applied broadband white noise signal were determined
in both ground states and showed a strongly decreased dominant resonance frequency in the
lower ground state. The results also showed, that the asymmetry of the system causes different
switching behaviours for each bistable ground state, whereas it requires less energy to switch
from the lower to the upper ground state. Furthermore, it was demonstrated that a minimum of
two pulses are needed for switching when using positive rectangular pulses of 30 Vpp in contrast
to four when applying negative pulses. The pulse frequency causing switching was in the range
of 60-110 kHz, strongly depending on the geometry and applied signal scheme. Additionally, a
positive voltage offset applied to the pulse signal characteristics resulted in both a wider range
of frequencies suitable for switching and in a decrease of the dominant resonance frequency,
which is also beneficial for the switching process and indicates the potential for efficient
switching of bistable MEMS membranes.

http://dx.doi.org/10.1088/1361-6439/ab3185