磁流體實驗

Role of magnetic fluidsRole of magnetic fluids

In the early 20th century In the early 20th century Solid state physicsSolid state physics

Nanoparticles

Nanostructured materials

Nanodevices

Nanoparticles

Nanostructured materials

Nanodevices

Nanoscale science & technology

Nanoscale science & technology

1960 ~1960 ~

Including Soft Materials : Fluids Liquid crystals Polymers Emusions Colloids

Including Soft Materials : Fluids Liquid crystals Polymers Emusions Colloids

Condensed matter physics

Condensed matter physics

Magnetic fluidsMagnetic fluids

OutlineOutline

• What Is Magnetic Fluids (Ferrofluids)? • Properties of Magnetic Fluids• Properties of Magnetic Fluid Thin Films under Mag

netic Fields (perpendicular/parallel) Ordered Structures of Magnetic Fluid Films Optical Properties of Magnetic Fluid Films• Outlook

• What Is Magnetic Fluids (Ferrofluids)? • Properties of Magnetic Fluids• Properties of Magnetic Fluid Thin Films under Mag

netic Fields (perpendicular/parallel) Ordered Structures of Magnetic Fluid Films Optical Properties of Magnetic Fluid Films• Outlook

100 Å

Magnetic particle Surfactant ( 界面活性劑 )

Liquid Carrier

What Is Magnetic Fluids (Ferrofluids) ?What Is Magnetic Fluids (Ferrofluids) ?

Properties of Magnetic Fluids

Fundamental Properties- Magnetic Characterizations -- Magnetic Characterizations -

H I/r

I = 0 I 0

- Thermal Conductivity -- Thermal Conductivity -

Magnetic fluid has good thermal conductivity.

(Air: 26.2 mW/m/k @ T = 300 K)

- Loudspeaker (high thermal conductivity of MF) -- Loudspeaker (high thermal conductivity of MF) -

0 5 10 15Tim e (m in)

0

40

80

120

160

Coi

l tem

pera

ture

(o C

)

Input signal: 300 H z 40 W

Air

M agnetic flu ids

ApplicationsApplications

Oil

Magnets

Magnetic fluidLiquid Research Ltd.

- Sealing of magnetic fluids -- Sealing of magnetic fluids -

S

N

High-pressure region

Low-pressure region

MF

- Other Applications- Other Applications

•Inkjet printing : coding (magnetic particles)

•Surface polishing (nanoparticles)

Most applications are focused on mechanical purposes.

Applications in bio-medical and optical-electronics are new interesting topics

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Preparation of Magnetic Fluids

Fe3O4

Dextran

Water mixingNH4OH

co-precipitate, Fe3O4

removing salt residue & large particles

removing unbound dextran

coating

centrifugal

gel filtration chromatography

homogeneous water-based Fe3O4 magnetic

fluid

dextran

H2O FeCl2 & FeCl3

FeCl2 + FeCl3+8NaOH → Fe(OH)2 + Fe(OH)3 + 8NaCl

• Fe(OH)2 + 2Fe(OH)3 → Fe3O4 + 4 H2O

Properties of Magnetic Fluid Thin Films under Magnetic Fields

(perpendicular/parallel) Ordered Structures of Magnetic Fluid FilmsUnder Perpendicular Magnetic FieldsUnder Parallel Magnetic Fields

Optical Properties of Magnetic Fluid FilmsMagnetochromatics (perpendicular)Birefringence (parallel)Transmittance (perpendicular/parallel)Refractive Index (perpendicular)

H

H.E. Horng et al., JAP, 81, 4275(1997) APL, 75, 2196(1999) APL, 79, 2360(2001)

Magnetic fluid

Si wafer/ glass

Top View

glass

- Formation of Ordered Structure in a Magnetic Fluid Film -

Ordered Structures of Magnetic Fluid Films

Ordered Structures of Magnetic Fluid Films

Under Perpendicular Magnetic FieldsUnder Perpendicular Magnetic Fields

Magnetic fluid filmMagnetic fluid

Au

- Observation of Ordered Structure in a Magnetic Fluid Film -- Observation of Ordered Structure in a Magnetic Fluid Film -

H = 53 Oe, d = 5.14 m

H =200 Oe, d = 3.36 m

H = 77 Oe, d = 3.36 m

H = 210 Oe, d = 3.27 m

H = 34 Oe

H = 560 Oe, d = 2.37 mH =630 Oe, d = 2.37 m

H = 0 Oe

5 m

Ms = 5.6 emu/g, T = 18.0 C, dH/dt = 5 Oe/s, L = 6 m

H

~1 m, h~6 m 107 ~ 108 particles

Fast Fourier Transformation

H

10 mThe ordered structure is characterized by d (distance between two neighboring columns, d varies from submicron to several m): d = 2d = 2/k/k

r

H.E. Horng et al., JAP, 81, 4275(1997) APL, 75, 2196(1999) APL, 79, 2360(2001)

磁點排列成

六角形分佈

Sweep rate

Film thickness

Concentration

Temperature

Material

.

.

.

- Control Parameters for the Magnetically Tunable - Control Parameters for the Magnetically Tunable Ordered Structure -Ordered Structure -

Well-controlled and tunable ordered structure

Important Result:

Magnetochromatic Effects in Magnetic Fluid Thin Films

H.E. Horng, Chin-Yih Hong, Wai Bong Yeung, and H.C. Yang

Cover page of Applied Optics, Vol. 37, 1 May(1998)

Magnetochromatics (perpendicular)Magnetochromatics (perpendicular)

A: PC B : CameraC: Solenoid D : Magnetic fluid film E : Mirror F : Telescope G : White source H :Current source I : Lens J : Aperture

C

E G

H

F G

D

B

A

I J I

H.E. Horng et al., Appl. Opt., 37, 2674(1998) JAP, 83, 6771(1998) JAP, 88, 5904(2000)

Optical Properties of Magnetic Fluid FilmsOptical Properties of Magnetic Fluid Films

H = 50 Oe (d = 2.34 m)

H = 100 Oe (d = 2.26 m)

H = 200 Oe (d = 1.64 m)

- Controllable Magnetochromatics -- Controllable Magnetochromatics -

Under Parallel Magnetic Fields

Under Parallel Magnetic FieldsUnder Parallel Magnetic Fields

- Periodic one dimensional grating -- Periodic one dimensional grating -

H = 200 OedH/dt = 100 Oe/s W = 10 μm L = 1.5 μm Ms = 17.6 emu/g td = 3 min Δx = 1.45 μm

H

10 m

x

Magnetochromatics of the Magnetic Fluid Film under a Dynamic Magnetic Field

Herng-Er Horng, S.Y. Yang, S.L. Lee, Chin-Yih Hong, and H.C. Yang

Appl. Phys. Lett., 79, 350 (2001)

H(Oe) 60 200

= 15.2o

Applications of Magnetic Fluids

Future Works

We have well controlled and understood the ordered structures and the optical properties of the magnetic

fluid thin films.

We have well controlled and understood the ordered structures and the optical properties of the magnetic

fluid thin films.

NTNUNTNUNTNUNTNUMagnetic Field Dependent nMF

(H)

0 30 60 90 120 150 180 210 240 270H (O e)

1.4350

1.4400

1.4450

1.4500

1.4550

Ref

ract

ive

inde

x, n

MF

M s = 0.68 em u/gdH /dt = 10 O e/s = 1.557 m

L = 80 m10 m10 m

The nMF is increased under a higher field.

The increase in nMF is suggested to be due to the column formation.

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Working Principle

Magnetic fluid core

(a) H = 0, ncore > nMF, total reflection occurs

(b) H 0, ncore< nMF, total reflection vanishescladding

IH=0

IH0

IH0 < IH=0IH0 < IH=0

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Modulation of Transmitted Light Intensity

0.00 10.00 20.00 30.00 40.00Tim e (s)

-8 .00

-4.00

0.00

4.00

0

200

400

273 Oe

180 Oe

100 Oe

60 Oe

Transmission loss =(IT-IT,H=0)/IT,H=0

H (

Oe) L = 796 m

Ms = 0.61 emu/g

Tra

nsm

issi

on lo

ss (

%)

H

Transmission

axis

Polarizer

Sample

He-Ne laser ( = 632.8 nm)

- Experimental Setup- Experimental Setup

Ein

Eout

w/0.01o resolution

Analyzer

Transmission axis

0 30 60 90 120 150 180 2100.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

(

deg)

H (O e)

L = 6 mM s = 6.4 em u/gdH /dt = 50 O e/s

-H

NTNUNTNUNTNUNTNUSummary

The refractive index of magnetic fluid films can well manipulated.

The feasibility of the magnetic-fluid-based optical modulator and switch is demonstrated.

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Conclusions

Magnetically labeled

immunoassayPhotonic Crystal

Modulator

CWDM

Switch What else?

Magnetic fluids