characteristic evaluation of a solid polymer electrolyte sensor
TRANSCRIPT
TECHNICAL PAPER
Characteristic evaluation of a solid polymer electrolyte sensor
Manabu Otsuki • Takeshi Okuyama •
Mami Tanaka
Received: 4 September 2010 / Accepted: 28 March 2011 / Published online: 19 April 2011
� Springer-Verlag 2011
Abstract This paper describes a development of a cur-
vature sensor using a solid polymer electrolyte (SPE) film.
The SPE film has good flexibility, and can be used in air. In
previous research, we clarified output response to defor-
mation of the SPE sensor and the relationship between
sensor output and sensor curvature. In this paper, output
characteristics of the SPE sensor are investigated in detail.
Four sensors with different length and width are prepared.
And the influence of the SPE sensor on the sensor element
shape is investigated. As a result, it is confirmed that there
are a several sensors which cause a slight reduction of the
sensor output because it is difficult to place the whole
sensor element on the sample curve exactly. Concerning
with the large sensor, it was confirmed that the reduction of
the sensor output is not occurred.
1 Introduction
Recently, functional polymers including PVDF with pie-
zoelectricity and ionic polymer metal composites (IPMC)
have been attracting attention, and several actuators and
sensors have been developed (Shahinpoor 1998). In gen-
eral, the functional polymers have advantages such as
lightweight, flexibility and good workability. And they
have another advantage that an external power supply is
unnecessary, because functional polymers can convert
electrical energy into mechanical energy by itself and can
convert reversely. Especially, IPMC attracts attention in
broad fields as an actuator which makes large bending
deformation by low voltage (Konyo et al. 2000). IPMC has
been investigated as a sensor, too (Bonomo et al. 2008).
However, IPMC has the water evaporation problem in air.
Therefore, a solid polymer electrolyte (SPE) has been
expected as a functional polymer which makes deformation
by adding voltage like IPMC in air (Cho et al. 2007).
Authors have been developing an SPE sensor which has
a layer structure. Fundamental characteristic evaluation of
the sensor was carried out. It was observed that the output
voltage of the sensor is associated with bending deforma-
tion (Okuyama et al. 2009). Moreover, it was found that
output voltage of the proposed sensor is proportional to the
average of the curvature over the whole sensor element
(Otsuki et al. 2009). However, in previous study, the
influence of the sensor shape on the sensor output is not
considered.
In this paper, output characteristics of the SPE curvature
sensor are investigated in detail. Four sensors which have
different area size were prepared. Two of the sensors are
square-shaped and the other two are rectangle-shaped. The
influence of the SPE sensor on the sensor element shape is
investigated.
2 Structure of SPE sensor
Figure 1 shows the photograph and the structure of the SPE
sensor. The sensor element has a basic structure that an
SPE film is sandwiched between thin carbon films coated
with Ag paste. In addition, they are covered with polymer
films. And polyvinyl chloride film as a gripper is set around
the sensor. Output voltage of the SPE sensor was generated
M. Otsuki (&) � M. Tanaka
Graduate School of Biomedical Engineering, Tohoku University,
Sendai, Japan
e-mail: [email protected]
T. Okuyama
Graduate School of Engineering, Tohoku University,
Sendai, Japan
123
Microsyst Technol (2011) 17:1129–1133
DOI 10.1007/s00542-011-1285-z
by applying bending deformation. Although the output
generation mechanism of SPE sensors has not yet been
elucidated, the difference in electric double layer capacity
between the anodic and cathodic interfaces may be gen-
erated by applying bending deformation (Saito et al. 2009).
Dimensions of four sensors are listed in Table 1. Based
on shape (rectangular: R or square: S) and the size of the
sensor element (100, 200, 400, 900 [mm2]), four sensors
were described by the abbreviation. For example, R100
indicates the sensor with rectangular shape and the size of
100 mm2. Moreover, l means the length of the long side
and w means the length of the short side.
3 Experiment
3.1 Measurement condition
The influence of the sensor shape on the sensor output was
investigated. Ten kinds of acrylic cylinders whose radii are
10 to 50 mm were prepared as measurement sample as
shown in Fig. 2.
To perform the all measurements at unified position on
the sample, three base lines on the sensor, which are line 1,
line 2 and line 3, and a reference line on the sample were
defined as shown in Fig. 3. The line 1 is defined as the
center line of the sensor element which is parallel to the
width direction. And the reference line which is parallel to
the cylinder axis was set on the curve of the sample as
shown in Fig. 4. And ‘sensor-rotation angle’, h, is defined
as the sharp angle between line 1 and the reference line.
For example, when line 2 was placed on the reference line
as shown in Fig. 4, h was p/4 rad. The measurements were
carried out for three kinds of h (e.g. h = 0: when line 1 was
placed on the reference line, p/4 and p/2: line 3 was placed
on the reference line).
In the experiment, the sensor was operated manually.
First, the sensor was placed on the flat, and the voltage
adjusted to zero. Next, the sensor was placed on the curve
of the sample at three kinds of h as shown in Fig. 4. Then
the sensor was carried back to the flat. The output voltage
Ag pasteSPE material
Carbon films Polymer film
a
b
Fig. 1 Photograph and structure of the SPE sensor. a Photograph of
four sensors. b Cross section of the sensor on side view
Table 1 Properties of four sensors
Sensor symbol l (mm) w (mm) Area size of sensor
element (mm2)
R100 20 5 100
R200 20 10 200
S400 20 20 400
S900 30 30 900
Fig. 2 Measurement samples
π/4 radθ
Line 1
Line 2
Line 3
Sensor element
Lead
Center of the sensor element
l
w
Fig. 3 Positional relation between three base lines and the sensor
element
1130 Microsyst Technol (2011) 17:1129–1133
123
was measured using a data logger (KEYENCE products
NR-500, ST04, input impedance of 1 MX) at sampling rate
of 100 Hz. The sensor was kept on the sample for about
10 s. Output was measured five times for each condition.
The measurement was carried out at room temperature.
3.2 Result
Figure 5 shows the output voltage waveforms from S900 at
0 rad for the sample with 10 mm radius in five times
measurements. As the sensor was placed on the sample, the
output voltage increased. While holding on the sample, the
output was relatively constant. When the sensor was car-
ried back to the flat, the output voltage was back to zero.
The transient responses of the output are different for each
measurement due to manual operation. However, by
comparing the sensor outputs from five times measure-
ment, it was confirmed that the sensor output converge a
constant value under constant deformation. The average of
the sensor output with 25–30 s after beginning of the
measurement was calculated. In evaluation of the sensor,
the average value was used as the sensor output.
Figure 6 shows the relationships between the sensor
output and curvature for four kinds of sensors at 0 rad. For
all sensors, the relationship between the sensor outputs and
curvature are approximately in agreement.
Figure 7 shows the relationship between the sensor
output and curvature for three kinds of h for each sensor. In
the case of S400 (Fig. 7c) and S900 (Fig. 7d), the rela-
tionship between the sensor output and curvature is not
affected by h. The results coincide with that in the previous
study (Otsuki et al. 2009). In the case of R100 (Fig. 7a) and
R200 (Fig. 7b), the output decreases slightly with rotating
the sensor to p/4 and p/2. Moreover, the amount of the
reduction increases with increasing the sensor curvature.
4 Discussion
In previous study (Otsuki et al. 2009), it is clarified that the
sensor output voltage corresponds with the average cur-
vature over sensor element. Therefore, when a part of
sensor element is not entirely fitted on the surface of
measuring object, the average curvature reduces. More-
over, according to increasing the ratio of small curvature
part on the sensor, the average curvature reduces, too. The
reduction of the average curvature results in the decrease of
the sensor output.
Focusing on sensor R100, R200 and S400, the sensor
output at h = 0 is the same, and the output at h = p/2 is
different. Moreover, the sensor element length parallel to
the circumferential direction of the sample is the same
relation. In fact, it is considered that the sensor output
decreases slightly with decreasing the sensor element
length parallel to the circumferential direction of the
sample.
Fig. 4 Aspect of measurement
0 10 20 30 40 50
0
0.2
0.4
0.6
Time (s)
Out
put v
olta
ge (
mV
)
Fig. 5 A typical response of the SPE sensor to measure the curve of
the sample
0 0.02 0.04 0.06 0.08 0. 10
0.1
0.2
0.3
0.4
0.5
0.6
Curvature (mm−1
Sens
or o
utpu
t (m
V)
R100R200S400S900
)
Fig. 6 The sensor output versus the sensor curvature for four kinds of
sensors
Microsyst Technol (2011) 17:1129–1133 1131
123
Due to the manual operation, it is difficult to place the
whole sensor element on the sample curve exactly.
Therefore, it is considered that the gap between the sensor
element rim and the sample curve is occurred although the
gap is so small that it is seldom visible to the naked eye.
The influence of the gap on the sensor output increases
with decreasing the sensor length and width.
Furthermore, by comparison of S400 and S900, the
dimensions are different. However, the output character-
istic of the sensor was almost the same. The results suggest
that there is the critical width and length so that the
reduction of the average of the sensor curvature is occur-
red. The reason is as described above.
5 Conclusion
In this paper, characteristics of the SPE curvature sensor
were evaluated. As a result, it was confirmed that the
output voltage of the small sensor decreases slightly
because it is difficult to place the whole sensor element on
the sample curve exactly. Concerning with the large sensor,
it was confirmed that the reduction of the sensor output is
not occurred.
Acknowledgments The authors wish to thank Mr. Nozomu Sugoh,
Mr. Taketoshi Okuno and Mr. Ryota Komiya (KURARAY CO.,
LTD.) for providing us the sensor material.
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