Novel Functional Materials--Carbon Microcoils/（CMC）-Properties and Potential Application
Dr. Seiji Motojima
Fellow
Toyota Physical ＆ Chemical ResearchInstitute

Prologue to selendipitic discovery of silicon
nitride microcoils and carbon microcoils ------Beautiful face of ceramic single crystals
obtained from high corrosive
atmosphere using CVD process------・ Reaction temperature： 800～2500℃
・ Corrosive atmosphere: HCl, H2S, etc
・ Crystal size: 10~500μm

Golden prizes got in the Micrograph Exhibition for Ceramics Crystals(Ceramic Society of Japan)

1981

1987

1981

1988

1981

1989

1987

1989

1992

Cover photographs of the Journal of Ceramics

2000

2002
2006

Fe, 1200℃
Si3N4 whiskers (microcoils), Nature，339(1989)179
Si2Cl6+NH3+H2

5 um

Carbon Microcoils (Appl. Phys. Lett., 56(1990)321.

What is CMC (Carbon microcoils) ？
1) A kind of vapor grown carbon fiber (VGCF)
2) Preparation process: by metal catalyst-activated CVD・Carbon source: acetylene (for weld）
・Catalyst: Ni, Fe-Ni, etc.
・Reaction temperature: 750-800℃
3) Morphology:3D-Helical/spiral structure4) Dimension: ・Coil diameter: ～μm
・Coil Length ～10mm5) Microstructure: Amorphous
6) Characteristics： ・Coiling-chirality
・High-elasticity
・High interaction with microwaves

Critical difference of CMC from carbon nanotube

Reaction tube for the preparation of carbon microcoils (CMC)＋Ｈ２Ｓ＋Ｎ２）

Catalyst

Arrow：Catalyst grain (Ni). Rotating at 60 rpm

Double-helix Carbon Microcoils(CMC)

L

L

R

Double-helix carbon microcoil (flat-type)
Commercially available
representative CMC

Regular Right-hand Carbon Microcoils

Regular left-hand Carbon Microcoils

Single-helix Carbon Microcoils

CMCs with various interesting morphologies (1)CMCs with various interesting
morphologies (2)R
Catalyst Grain
Twinned single-helix CMC
grown from a catalyst grain
Arrow indicate a catalyst grain

LSuper-helix CMC

Super-helix carbon nanocoils (Catalyst: Fe, 700 ℃）

（Catalyst: SUS 304)

Single-helix CMC(Catalyst: Fe-Ni)

Cover photographs of Journals

These interesting micrographs were published as coverphotographs of international journals.

Microstructure of as-grown CMC
Palm
hull-based A.C.
ヤシガラ活性炭

木質活性炭A.C.
Wood-based

Coaltar-based A.C.
コールタール活性炭

As-grown CMC

TEM (lattice) image of as-grown CMC

XRD pattern of as-grown
CMC and activated carbon

XRD patterns ( left) and Neutron diffraction analysis (right) of as-grown CMC
and heat-treated CMC in CO+CO2 or Ar atmosphereHeat treatment
temperature( in Ar, for 3 hrs)

Influence of heat-treatment temperature on the spring constantHeat treatment
temperature( in Ar, for 3 hrs)

Videos showing the extension and contraction of as-grown CMC

A piece of CMC

Bulk CMC as-grown on thesubstrate

Extension

Extended forms of as-grown CMC to the right and left directionExtended Carbon Microcoils

Extension

Extension

Mechanical stability of CMC
Source CMC
Characterization process
CMC （0.3ｇ）/1,2-Dichloroethane（60ml）
stirred by magnetic stirrer in conical beaker (100ml)
for 6 days

After 6 days
stirring

StirrerS-s curves of CMC under applied load
For a single coil

Applied Load (mg)for Bulk coils

Extendedlength(mm)
伸びcoil”δ”(μm)

Another importantcharacteristics of CMC
is changing in electricalparameters under theextension orcontraction of the coils。
This figure shows therelationship between
the extension andelectrical resistivity.
It can be seen that theelectrical resistivity
increases with theextension anddecrease with thecontraction. Other
electrical parameter,
such as L, C, Z, θalso changes by theextension orcontraction.

As-grown CMC

Heat-treated
CMC

VGCF

Influence of coil diameterand fiber diameter on thespring constant of asgrown CMC

Interaction of CMC with EM wave
CMC with 3D-Helical/spiral form
Electromagnetic (EM)Wave

Generation of inductive electromotive
force
electric current
Joule`s Heat

Faraday`s Law of Electromagnetic Induction

Generation of inductive
electromotive force

Generation of inductive electromotive force

Application
to magnetic
sensorelement

Relationship between
magneto-resistanceand magnetic field ofa piece of CMC.

Application to micromagnetic sensor
Connecting Au electrodes to a single coil using FIB

Electric
Current

Au Electrode

Au
ElectrodeVisualization of magnetic flux by en Electron pholographExperiment

Estimation

Distribution image of magnetic flux lines

Application to laser sensor
100
インピーダンスの変化量
Δ Z [Ω ]100
インピーダンスの変化量
Δ Z[Ω ]

80

80

60

60

40

40

20

20

0

-20
400

0
500

600
700
レーザ波長λ[nm]800

Relationship between wavelength of laser and
impedance of a piece of CMC.
(Measured frequency=1kHz、Laser
power=300μW)

0

100

200
300
光の強さW[μW]

Relationship between laser power and
impedance of a piece of CMC.
(f=1kHz、λ=405nm)

400Application to ｆield emitterワイヤレス独立機能型CMCインテリジェント
センサー（イメージ図）
CMCの電磁波吸収特性

CMCインテリ
ジェント
センサー
ID No.０００００

0-5

CMCインテリ
ジェント
センサー
ID No.０００００

信号交換

R e fle c tio n L o ss (dB )電力供給用電波

-10
-15
-20

0.1%
0.5%
1%
1.5%
2%
3%
5%
10%

-25
-30
-35

CMCインテリ
ジェント
センサー
ID No.０００００

信号送信

受信機
コンピュータ-40

受電用CMC -45
12.4
マイクロアンテナ

32.4

52.4

72.4

92.4

Frequency (GHz)

信号送信用
CMC
マイクロアンテナ

計測・制御
CMC Technology Development Co., Ltd.

Potential application in micro antenna
Micro antenna of various types are prepared.

Dipole-type

Dielectrics-type

Characteristics of micro-antenna for space development
10
11.5GHz
13.5GHz

0

0

340

350
10

-10

Gain[dBi]

20
30

330
320

Gain[dBi]

10

40

0

50

310
300

60

-10

70

290

-20

-20

280

-30

270

-30

80
90
100

260

リード線(比較用)
CMCAT-001
CMCAT-002
CMCAT-003
CMCAT-004

-40
-50

250

110

240

120

230

130
220

140
210

150
200

190

170

160

180

Radiation pattern

-60

1.0
1.0

Gain ratio

10.0
10.0

周波数[GHz]
ネットワークアナライザ

ホーンアンテナ
試供体

30.0 [GHz]100.0

共試体 ホーンアンテナ

パソコン等

電波吸収体
ターンテーブル

Measurement/evaluation system

ターンテーブル

ネットワークアナライザー

CMC Technology Development Co., Ltd.

CMC-Containing Fibers
ＣＭＣ／Keratin fiber

ＣＭＣ／ＰＬＡ Fiber

繊維径２４ﾐｸﾛﾝ、約５デニール

CMC-keratin clothCMC(3wt%)/PET fibers

Characteristics of CMC as reinforcing fibers
Stress-strain diagram of CMC/Epoxy resin（Young’s modulus:700MPa）composite
50
Tensilestrength（MPa）

Stretch（%）

Young’smodulus
（MPa）

Blank

42

65

690

Carbon fiber(3wt%）

44

67

750

ＣＭＣ
3wt%

40

51

720

Epoxy matrix
Carbon fiber
Carbon micro-coilStress(MPa)

40

30

(n=3)

20

Straight carbon fiber composite
10

Tensile strength, Stretch andYoung’s modulus: slightly increased0

CMC composite
・ Tensile strength：slightly decreased
・ Stretch, Young’s modulus: slightly
increased

050
Strain(%)

Stress-strain diagram of CMC/Epoxy resin（Young’s
modulus:1MPa）composite
1.0
Tensilestrength（MPa）

Stretch（%）

Young’smodulus
（MPa）

Blank

0.36
(σ=0.035)614(σ=36)

1.2(σ=0.12)

Carbon fiber(3wt%）0.56(σ=0.031)714(σ=61)

1.4(σ=0.13)ＣＭＣ（3wt%）

0.83

605

2.1

(σ=0.034)(σ=16)(σ=0.37)

Stress(MPa)

Epoxy matrix
Carbon fiber
Carbon micro-coil

0.5

Straight carbon fiber composite
Tensile strength, extension andYoung’s modulus: slightly increased
CMC composite
0.0
0

500
Strain(%)

Tensile strength, Young’s modulus:
increased by ca. 2 times

Application
to analytical
microsensor

Application as a microwave heating element

150

(Coil
length) Absorption of 2.45GHz(コイル長)

90μm↓
90～150μm
150～300μm
300～500μm
500～1000μm
1000μm↑シリコーン油のみ

Temperature
温度上昇(K)
increase (K）

120

90

60

CMC:
３ ｗｔ％

(Carbon
炭素粉末powder)(CMC 1.0wt.%)(Ferrite) フェライト

30

蒸留水( Water)(Siliconeoil)
シリコーン油

0
0

15

30

45

Irradiation
Time
照射時間
(s)(s)
Temperature increase of CMC( 1wt%)/silicone oil by microwave oven heating

CMC試料の温度上昇

“Electron Crucible” heated by amicrowave oven for ca. 15 min

IR Thermograph

Refractorybrick

Crucible in which
CMC are imbedded
High microwave absorption property of CMC is now applied in a microwave oven crucible.
That is, the CMC was embedded into ceramic crucible, and the crucible was heated for 10
min in microwave oven. The highest temperature was attained up to 1200℃

Commercially available representative CMC (powder-like forms)

CMC(1wt%)/PMMA Bead

CMC/PMMA Foam

1 mm

These are CMC and PMMA composite beads and foams.

10 mm

Visualization screen ofelectromagnetic field
Microwave（2.45GHz, λ=12
cm）

1 mm
CMC/PMMA beadThis is a microwave visualization panel which wasformed by the CMC/PMMA beads and was vertically set
in the central part of a microwave oven, and the formed
heat was visualized by an IR thermograph.

１ mm

Visualization of microwave （2.45GHz)
CMC(1wt%/PMMA

Microwave

CMC(10wt%)/PMMA

6 cm

60 mm

This is an IR thermograph of CMC panel after
microwave oven heating.The red part is a hightemperature part and microwave is concentrated inthese regions.
The distance between vertical patterns is about 6 cm,
which correspond to a half of wave length 12 cm of
microwave 2.45GHz.
It can be seen that microwave within a microwave
oven is not present in uniform but present
discontinuously with the separation of 6 cm.

Application to cosmetics(ng/ml)(ng/ml)Breeding effects of CMC on skin cells and collagen fibrils
This figure shows the effect of CMCs on the skin cell and collagens breeding. It can be seen that the number of skin cell; Pam
212,increases by 160% by the addition of CMC of 1000ng/ml、against a control sample, that is, without addition of CMC. In
the case of collagen fibrous too, breeding effect of the addition of CMC was observed.

CMC is also now applied
to cosmetics as shown inthis micrograph.
Very small amount of CMC
is added to compact
cosmetic powders.

Effect of CMCs for anti-breeding ofHela cell (human-uterus-neck-cancercell）（CMC : 0.04 wt%）

Applicable as cancer
remedy medicine

This figure shows the effect of
CMC on the breeding of cancer cell.
When the CMC was added by 0.04
wt%, the number of cancer cell after
7 day breeding is about 20% against
control sample.
That is, the CMC can be applicable
as a cancer remedy medicine.
Why CMC is affective for therecovery of skin cell or for cancer
remedy is not known yet.

Application to electro microwave absorber

Free space microwave measurement system (JFCC-HVS)

Carbon powder(d)Carbon powder(c)Ｔｈａｎｋ ｙｏｕ

CMC(B)
Carbon powder(b)Carbon powder(a)CMC(A)
Coil length:<1mm

CMC/Polyurethane

CMC+Microballoon+Al flake+Carbon Fiber+Carbon blackApplication to microwave absorber

Polyurethane

1 wt%
2 wt%
1.5 wt%CMC(1wt%）PMMA Foam(26mm)((() 300-500μm(1%)) 300-500μm(1%)/ 300-500μm(1%)) 300-500μm(1%)/ 150-300μm(1%)

300-500μm(1%)/ 150300μm(1%)

5 wt％
10 wt％
１wt％
CMC/PMMA Bead

3 wt%
1 wt%

Reflection loss of CMC/PMMA foams （CMC:１５０－３00μm)

Single sheet (150-300μm, 3 wt)(150-300μm, 3 wt%)/(150-300μm, 1 wt%)
(150-300μm, 3 wt%)/(150-300μm, 1 wt%)
CMC/PMMA Foam: Total thickness of absorbing layer: 26 mm.
(CMC coil length and content of CMC in PMMA) :() single sheet (150-300μm, 3 wt%), () doublesheet (150-300μm, 3 wt%)/(300-500μm, 1 wt%), ()
double sheet (150-300μm, 3 wt%)/(150-300μm, 1 wt%).

Change in electrical resistivity of CMC/polysilicone composite
sheet in relation with the addition amount of CMC

10

7

10

6

10

5

10

4

10

3

10

2

Resistivity (Ω cm)

10

8

0

CMC
Vapor grown
VGCF carbon fiber
CarbonCB
powder1020
30Volume fraction (%)

40

Change in electrical resistivity of composites under
applying compression stress of 0.1~0.2MPa)(Vapor Grown Carbon Fiber)

8

10

7

10

6

10

5

10

4

10

3

0

2vol%
4vol%
6vol%

5
Strain (%)

10

10

8

10

7

10

6

10

5

10

4

10

3

2vol%
4vol%
6vol%

0

5
Strain (%)

for ＣＭＣ(4vol%) composite
Under applying
load of 0.1～0.2
MPa (1～2
kgf/cm2)

Under the deformationof 10％ compression or
tensile stresses

CB composite
Resistivity (Ω cm)

10

VGCF composite
Resistivity (Ω cm)

Resistivity (Ω cm)

CMC composite(Carbon Black)

10

10

8

10

7

10

6

10

5

10

4

10

3

0

15vol%

20vol%
25vol%

5
Strain (%)

Applicable as atactile sensor element

Changing inelectrical resistivity
by 1,000 times

10Change in electrical resistivity of composites under
applying compression stress

8

10

7

10

6

10

5

10

4

10

3

2vol%
4vol%

0

6vol%

5
Strain (%)

10

10

8

10

7

10

6

10

5

10

4

10

3

0

2vol%

Resistivity (Ω cm)

10

CB
composite

VGCF
composite
Resistivity (Ω cm)

Resistivity (Ω cm)

CMC
Composite

4vol%

6vol%
5
Strain (%)

10

10

8

10

7

10

6

10

5

10

4

10

3

0

15vol%

20vol%
25vol%
5
Strain (%)

10Model of various receptors of human skin(by Prof. T. Maeno of Keio Univ.)
1) Meissner’s
corpuscle is ahelical receptor of
cocoon-like forms,
which is formed by
the coiling of theterminal of nerves
fibers.
2) Meissnor’s
corpuscles arepresent in twoarrays under finger
prints with thedensity of
1500/cm3.
3) Meissnor’s
corpuscles showsa high sensitivity
and discrimination
ability to applied
physical stimuli.

(Slow adapting-narrow)(Fast adapting-wide)

Finger Prints

・ Human skin has very high sensitivity anddiscrimination ability to various stresses and stimuli,
such as, mechanical loading, pressing, picking, sticking,rubbing, temperature, sound, etc.
・ So, It is expected that if CMC is embedded into elastic
rubbers, high tactile sensing and discrimination ability
corresponding to that of human skin may be obtained.
・According to this concept, we have prepared artificial
skin with tactile sensing properties. These sensor
elements were made of CMC and elastic polysilicone
rubber composite sheet.

・ So, it is expected that if CMC is embedded into elastic
rubbers, high tactile sensing and discrimination ability
comparable to that of human skin may be obtained.
・According to this concept, we have prepared artificial
skin with tactile sensing properties. These sensor
elements were made of CMC and elastic polysilicone
rubber composite sheet.

Meissner’s Corpuscles
・ 3D helical-coiled nerve fibers(Proteins)・ Single-helix ?
・ Diameter of helix : 40-70 μm
・ Length of helix : 20-150 μm

Carbon Microcoils(CMC)
・3D helical-coiled carbon fibers(Pure carbon)
・Double-helic or single-helix
・Diameter of coils : 1-20 μｍ
・Coil Length : 50-500 μｍ

Relationship between Meissner’s corpuscle and carbon micorcoils
There are many similarity between Meissner’s corpuscle andcarbon microcoils in the point of conformation and size

Model of CMC/Polysilicone Micro-sensor Element

Structure of CMC Sensor element

Carbon microcoils(90-500μm, 1~5wt%)

Sensing applied verysmall load, pressure,temperature,electromagnetic waves,sound, etc. with very highsensitivity anddiscrimination ability.

Matrix(Elastic Polysilicone)

Electrode(50-200KHz,
0.5-10V)

Ｍｉｎｉaｔｕｒｉｚａｔｉｏｎ Ｐｒｏｃｅｓｓ

Cut

Cut
The CMC sensor element have avery simple structure, composite
of CMC and elastic matrix, andcan be easily miniaturizing by
cutting successively the large
sheets to small sheets or blocks
by using conventional cutter orultrasonic cutter. The minimum
size of obtained sensor element
was about 100x80x80mm3

C（F）
Change in LCR parameters of
micro-sensor （100ｘ100ｘ100
μm3 )

50fF

Matrix： Elastic silicone resin
Coil Length： 500-500μm
Coil Diameter： 1-10μm
Addition amount： 5ｗｔ％
Load： 0.5ｇf

L（H）

R（Ω）

1mH

100 Ω

Change of LCR parameters
under applying very small loads
Addition amount of CMC: 1wt%
Coil Length: <300 μm
Thickness of element： 100 μm
Separation of electrode: 2.5mm

C

４００ｆF

Minimum detectable load： 1mgf (comparable to human skin)

500mg

L

200mg

R

100mg
50mg

１００ｍH

20mg
10mg

5mg
1mg 2mg

４０ｋΩ

The CMC sensor element has proximity sensing property as well as tactile sensing property

Approaching

Change in LCR parameters
under approaching a handto CMC sensor element
The CMC sensor element can detect accessing
substances to the elements without touching.

Separation between asensor element and a hand

Change in impedance (z) of the CMC sensor element
under approaching and touching to a Cu plate
ＣＭＣ1％ (電極間2mm)
96000

CMC（１wt％)/polysilicone
92000

200KHz

|Z|/Ω

88000

84000

80000

76000
0

10

20

30

40

50

60

Distance試料台(ＣＭＣサン
between CMC sensor
element and Cu plate
プ ル用)-金属板の距離/mm

70

Effect of target substances on the change in impedanceInfluence of the area of target object on the gain of proximity signal

Without
objectCMS was dispersed uniformly in thematrix, while the CMC did not form
a percolation structure (electricalcontact).

Possible tactile sensing mechanism of CMC sensor element(Formation of Complex Electric Equivalent Circuit)

CMC
Electric Equivalent Circuit

Mechanical Dynamic Model

MatrixＲ
Ｌ

Ｃ
Ｃ(ＬＣＲ Complex Resonance Circuit)(Spring Material Point Model)
CMC Technology Development Co., Ltd.

Possible proximity sensing mechanism of CMC sensor element(Changing in space capacitance by accessing conductive substances)

Cu plate

CuElectrodeApplications to medical
instruments for low
invasive surgery

Endoscope

CMC Sensor

Forceps

CMC Sensor

Forceps

Application to the advanced medical instruments

CMC Sensor
CMC Sensor

X-ray Diagnostic Instruments

Application to safety rotary door or elevator’s door

Stop/
停止・開放
opening

Stop/
停止・開放
opening

Stop/

減速・停止
opening
Red line赤線がセンサー装着部位
indicates CMC sensor element

CMC-Containing Fibers
CMC/Polyurethane
fibersCMC/Pulp Paper

CMC:20 wt%

CMC:50 wt%

2cmPreparation of Ceramic Microcoils/microtubeｓ
using CMC as a Template (by the high temperature vapor phase diffusion process)TiC/CMC Microcoils

TaC
Microtube

TiO2 microcoil

Applicationof Carbon
Microcoils

Initial growth stage of CMC

Top-view of CMC （arrow: Ni catalyst）

Side-view of CMC (arrow: Ni3C single crystal)
Catalyst grain

2D-growth model of CMC

Coiling mechanism based on the anisotropic property of catalyst
grain

Catalyst crystal

Circular coil

Flat coil