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energy generating and the supply method for the sensor
power supply are developed, the realization and the op-
eration of the marine sensor network will be easy, and
this kind of system has the environmental and the eco-
nomical advantages [4].
There are two kinds of the vibration energy harvesting
method from material point of view. One is the PZT
(Lead-Zirconate-Titanate) actuator method, and the other
is EAP actuator method. The wake-up circuit, power
management circuit, rectifier and MOSFET (Metal-Ox-
ide Semiconductor Field Effect Transistor) have been
researched because the harvested energy quantity from
the vibration energy is very low for the material limita-
tion and structure characteristics [5-9].
In this study, the sample which consists of a acrylic
elastomer (VHB4905 film from 3 M), conductible car-
bon grease(from MG chemical) and electric wire for the
basic study of an energy harvesting strategy and tech-
nique using EAP actuator was fabricated, and the con-
ductible carbon grease was used for an electrode. The
characteristics of the fabricated sample were analyzed
through the experiment. We also mixed carbon grease
with aluminum powder for conductibility improvement,
and the effect of the mixed electrode was confirmed
through the conductivity measurement which is derived
from the output voltage and the output current from the
fabricated sample with a mixed electrode.
2. Experimental Apparatus
2.1. Principal of Energy Harvesting
Figure 1 shows the principal of the electrical energy
production when the conductible polymer is used for the
energy generation. The energy density, , of the electric
field when Maxwell stress is not considered is expressed
as Equation (1).
u
2
0
1
2
u
E
(1)
where,
means the relative permittivity and 0
is the
permittivity (8.85 × 10–12 F/m) in the free space.
[V/m] is the electric field.
E
The electrostatic capacity, [C], which is derived
by the conductible polymer from the Figure 1 is de-
scribed as Equation (2).
C
0
Cz
(2)
where, is the length between two electrodes,
z
[m2]
is the cross-sectional area between electrodes. And the
electric field is expressed as Equation (3).
E
V
Ez
(3)
COMPLIANT ELECTRODES (2)
DIELECTRIC ELASTOMER
+V
out
(high)
+V
out
(high)
+V
in
(low)
+V
in
(low)
Figure 1. Energy generated from dielectric elastomer when
a force is impressed on compliant electrodes.
where, [V] means the voltage drop which is gener-
ated by the electrostatic capacity.
V
The outputted energy, [W], from the conductible
polymer is as Equation (4).
U
UuAz
(4)
We can get the final equation Equation (5) substituting
Equation (1) and Equation (3) for Equation (4).
2
1
2
UCV (5)
From the Equation (5), we can know that the energy is
outputted in accordance with the electrostatic capacity
change of the conductible polymer [9,10].
Figure 1 explains the energy generation state by the
electrostatic capacity change which is also governed by
the real external force. The electrostatic capacity is var-
ied if the length between the electrodes and the cross-
sectional area of the electrode are changed because the
electrostatic capacity is in inverse proportion to the sur-
face area of the polymer actuator and is also in propor-
tion to the length between the electrodes.
2.2. Experimental Setup and Procedure
Many kinds of EAP materials such as HS3 silicone,
Polyurethanes, Silicone NuSil CF 19-2186 and Acrylic
Elastomer are used for the energy harvesting mechanism.
In this study, the Acrylic Elastomer has been selected for
the energy harvesting material because this material has
characteristics such as a long displacement, a high oper-
ating force and a high density.
In this study, the Acrylic Elastomer of VHB 4905 film
from 3M was selected [11], and the electrode of the con-
ductible carbon grease from MG chemical was used for
the enough transformation for the flexible Acrylic Elas-
tomer [12].
Figure 2 shows the photo of the energy harvesting de-
vice which is the laboratory-made prototype and consists
of the Acrylic Elastomers, carbon greases and the electric
wires. The made energy harvester is two layered experi-
mental model. An Acrylic Elastomer was displaced at the
center position and the carbon grease with an electrode
was painted as a same height of 5 mm to the both side of
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