Preparation and property of diaphragm type CMC pressure sensor○Mika Kamei, Takashi Katsuno, Hironori Natsuhara, Toshikazu Sekine, Kazuaki Hashimoto*, Kyoko Miwa*, Keiji Kawabe**、Seiji Motojima（Faculty of Engineering, Gifu university, *Toukai Medical Products, **CMC Technical Development）(Abstract) Carbon micro coil synthesized by decomposition of acetylene gas have double helix structure. Therefore
electrical properties such as impedance |Z| and resistance were changed with extension-contraction of CMC itself.
CMC tactile sensor element obtained by mixing CMC with elastic matrix can detect contact pressure. Many
researchers have studied influence of size of element, matrices, configuration of CMC and CMC loading. Though,because of deformation difficulty of sensor element, it was hard to detect small pressure change at pressurized air.
In this work, in order to solve the problems, we tried to develop novel pressure sensor element leads tocomparatively large deformation induced by small pressure change, and did property evaluate.

Principle of CMC sensor

Prototype pressure sensor
Diameter：16 mm

CMC 7 wt%(300～500μm)

Length：30 mm+CMC/silicone
composite

GE Toshiba silicone
YE 5623
On sequentially

60200 mmHg

Inner CMC sensor element...

150 mmHg|Z|/kΩ

100 mmHg

50+50 mmHg
0 mmHg40
1.E+01Distance changeDeformation

5551|Z|/kΩ

Fig. 1. SEM image of double helix CMC.

Fig. 2. Photograph of CMC 18wt%/
polysilicone pressure sensor element.

47

43

1.E+03Frequency/Hz

1.E+050Fig. 3. Frequency properties of prototype pressure
sensor element in different pressure conditions.

50

100150Pressure/mmHg

200Fig. 4. Impedance change of prototype pressure
sensor element in pressurization.

Compression of CMC sensor element withpressurizing increase |Z|.

Electrical parameterchangeDiaphram sensor

Impedance Analyzer

Cu electrodes

Gas cylinder

Acrylic board

Manometer

Glass tube

Glass tube

CMC(18wt%, <90μm)/
polysilicone thin film

60

ReleaseValve

Valve

Fig. 5. Photograph of Diaphram sensor element.

0 mm H g

6050 mmH g

54

200 m mH g
R -150 m mH g
R -100 m mH g

42

2nd40

Ideal curve

R -50 mm H g

Pressurization

R -0 mm H g

1 .E+ 0 2
1 . E+ 0 3
Fr e qu e n c y/ Hz

1 . E+ 0 4

Fig. 7. Frequency properties of diaphram sensor
element in different pressure conditions.

30050★Conclusions★
①CMC/ polysilicone thin film wasdeformed by such a smallpressure change, leading toelectrical parameter change.

50|Z|/k Ω|Z|/ kΩ48

3rd

1st100 m mH g
150 m mH g

36
1 . E+ 0 1sensor

Fig. 6. Experimental equipment.

1 kHzDepressurization

100150 200 150 100 50
0Pres s ure/mmH g
Fig. 8. Impedance change of diaphram
sensor element applied different pressure.

Impedance |Z| increased with pressurizing and decreased with depressurizing. Since
excess deformation of thin film produced residual strain, when depressurize to 0 mmHg in
1st curve, |Z| value was different from start value. This phenomena also looked in start andfinish of 2nd and 3rd curve.

②In order to increase signal, weprepared diaphragm type CMC
pressure sensor element havingvery thin film. Though, we foundthat excess deformation of CMC/
polysilicone thin film produced
residual strain.
③We need to consider a novelstructure having quick recovery
and possibility of miniaturization.