Online proceedings - EDA Publishing Association

11-13 May 2011, Aix-en-Provence, France
Design and Development of Vibrational
Mechanoelectrical MEMS Transducer for
Micropower Generation
Rolanas Dauksevicius 1 , Genadijus Kulvietis 1 , Vytautas Ostasevicius 2 , Ieva Milasauskaite 2
1 Department of Information Technologies, Vilnius Gediminas Technical University
Sauletekio al. 11, LT-10223 Vilnius, Lithuania
2 Institute for High–Tech Development, Kaunas University of Technology
Studentu str. 65, LT-51369 Kaunas, Lithuania
Abstract- The paper is devoted to design, numerical
modeling and analysis of vibration-driven mechanoelectrical
MEMS transducer based on piezoelectric cantilever-type
microstructure, which function is to act as a micropower
generator in wireless sensor networks. This study also deals
with fabrication and experimental investigation of
piezoelectric PVDF thin films intended for energy harvesting
applications. The first part of the paper presents finite element
model of the transducer, which is a multiphysics one,
combining mechanics, piezoelectricity and fluid-structure
interaction in the form of squeeze-film damping governed by
nonlinear compressible isothermal Reynolds equation.
Subsequently the model is subjected to modal, harmonic and
transient analyses in order to determine the effect of viscous
air damping and geometrical parameters on device dynamical
and electrical performance. The second part of the paper
considers aspects of formation of PVDF thin films. The quality
of the produced thin films and their material characteristics
are evaluated by means of scanning electron and atomic force
microscopy as well as using X-ray diffractometry and FT-IR
spectrometry techniques. Performed experiments reveal that
fabricated PVDF samples possess distinct crystalline phases,
with alpha-phase being predominant.
I. INTRODUCTION
Constant progress in low-power electronics promotes
rapid development of large variety of battery-operated
portable, wearable, implantable and embedded devices
including autonomous wireless sensors, which have huge
potential in body area networks, condition monitoring and
ambient intelligence applications. Despite the fact that
energy density of batteries has increased by a factor of 3
over the past 15 years [1], frequently their usage has a
significant negative effect on device size and operational
cost. For example, conducting their maintenance for a largescale
sensor networks consisting of hundreds or thousands
of sensor nodes may be extremely unpractical and
uneconomical. In some cases batteries is not a feasible
solution, e.g. in providing reliable long-term power to
remote sensing systems that operate in harsh environments
such as downholes in mining, oil/gas extraction as well as
nuclear reactors, deep-sea or space applications. For this
reason alternative approaches are the subjects of active
research work worldwide. Several possibilities are
considered including [1,2]: (a) energy storage systems with
larger energy densities (e.g. miniaturized fuel cells),
however, still significant work is required for the realization
of commercial devices; (b) wireless powering solutions (as
employed in RFID tags), however, their tailoring for more
power intensive devices would require dedicated
transmission infrastructures; (c) harvesting ambient energy
by using vibration/motion or thermal energy, light or RF
radiation, acoustic noise, etc. Energy harvesters can
typically supply power in the range of 0.01 − 1 mW
depending on the employed conversion principle.
Meanwhile, the consumption of common wireless sensor
nodes is between 1 and 20 μW, with values reaching up to
100 μW for relatively complex nodes operating at high
data-rates [1]. Kinetic energy harvesting is particularly
attractive as structural vibrations are ubiquitous in the
environment. For example, it is well suited for supplying
energy to autonomous sensors in condition monitoring of
industrial machines or civil structures. Piezoelectric and
electromagnetic transduction mechanisms are considered to
be the most promising for vibrational harvesters, while
electrostatic devices are presently limited by their high
impedance and output voltages, which reduce the amount of
available current. Piezoelectric micropower generators
(PMPGs) have the advantages of relatively simple geometry
and fewer peripheral components. Moreover, it is not
difficult to integrate microelectronic circuits on the same
chip because the process for depositing both thin and thick
piezoelectric films is a fairly mature technology [2,3].
However, the majority of current micro-scaled PMPGs do
not generate sufficient energy to directly power most
electronics including MEMS-based devices. Significant
research efforts are currently focused on two principal
approaches for improving efficiency of these generators: (a)
development of hybrid micropower supply units comprising
both on-board storage and energy harvesting from
environmental vibrations, optimization of energy generation
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