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Magnetic Fluids: Properties, Structures, and Applications

Explore the role of magnetic fluids, including their properties, thin film characteristics, ordered structures, and optical properties. Learn about the preparation of magnetic fluids and their diverse applications across various industries.

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Magnetic Fluids: Properties, Structures, and Applications

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  1. 磁流體實驗

  2. Role of magnetic fluids In the early 20th century Solid state physics  1960 ~ Condensed matter physics Nanoscale science & technology  Including Soft Materials : Fluids Liquid crystals Polymers Emusions Colloids Nanoparticles Nanostructured materials Nanodevices Magnetic fluids

  3. Outline • What Is Magnetic Fluids (Ferrofluids)? • Properties of Magnetic Fluids • Properties of Magnetic Fluid Thin Films under Magnetic Fields (perpendicular/parallel) • Ordered Structures of Magnetic Fluid Films • Optical Properties of Magnetic Fluid Films • Outlook

  4. What Is Magnetic Fluids (Ferrofluids) ? Liquid Carrier 100Å Magnetic particle Surfactant (界面活性劑)

  5. Properties of Magnetic Fluids Fundamental Properties - Magnetic Characterizations - I 0 I = 0 H  I/r

  6. - Thermal Conductivity - Magnetic fluid has good thermal conductivity. (Air: 26.2 mW/m/k @ T = 300 K)

  7. Applications - Loudspeaker (high thermal conductivity of MF) -

  8. Magnets Oil Liquid Research Ltd. Magnetic fluid - Sealing of magnetic fluids - S High-pressure region Low-pressure region MF N

  9. - 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

  10. mixing coating Water FeCl2 & FeCl3 H2O NH4OH co-precipitate, Fe3O4 dextran Fe3O4 centrifugal removing salt residue & large particles Dextran removing unbound dextran gel filtration chromatography homogeneous water-basedFe3O4 magnetic fluid • Preparation of Magnetic Fluids

  11. FeCl2 + FeCl3+8NaOH → Fe(OH)2 + Fe(OH)3 + 8NaCl • Fe(OH)2 + 2Fe(OH)3→ Fe3O4 + 4 H2O

  12. Properties of Magnetic Fluid Thin Films under Magnetic Fields (perpendicular/parallel) Ordered Structures of Magnetic Fluid Films Under Perpendicular Magnetic Fields Under Parallel Magnetic Fields Optical Properties of Magnetic Fluid Films Magnetochromatics (perpendicular) Birefringence (parallel) Transmittance (perpendicular/parallel) Refractive Index (perpendicular)

  13. H  - Formation of Ordered Structure in a Magnetic Fluid Film - Top View glass Magnetic fluid Si wafer/ glass H.E. Horng et al., JAP, 81, 4275(1997) APL, 75, 2196(1999) APL, 79, 2360(2001)

  14. Ordered Structures of Magnetic Fluid Films Magnetic fluid film Under Perpendicular Magnetic Fields - Observation of Ordered Structure in a Magnetic Fluid Film - Magnetic fluid Au

  15. 5 m H = 53 Oe, d = 5.14 m H = 0 Oe H = 34 Oe H = 77 Oe, d = 3.36 m H  H =630Oe, d = 2.37 m H = 560 Oe, d = 2.37 m H = 210 Oe, d = 3.27 m H =200 Oe, d = 3.36 m ~1 m, h~6 m  107 ~ 108 particles Ms = 5.6 emu/g, T = 18.0 C, dH/dt = 5 Oe/s, L = 6 m

  16. Fast Fourier Transformation r 10 m The ordered structure is characterized by d (distance between two neighboring columns, d varies from submicron to several m): d = 2/k 磁點排列成 六角形分佈 H  H.E. Horng et al.,JAP, 81, 4275(1997) APL, 75, 2196(1999) APL, 79, 2360(2001)

  17. - Control Parameters for the Magnetically Tunable Ordered Structure - Sweep rate Film thickness Concentration Temperature Material . . . Important Result: Well-controlledandtunableordered structure

  18. 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)

  19. Optical Properties of Magnetic Fluid Films A B D I J I G F E G H Magnetochromatics (perpendicular) A: PC B : Camera C: Solenoid D : Magnetic fluid film E : Mirror F : Telescope G : White source H :Current source I : Lens J : Aperture C H.E. Horng et al., Appl. Opt., 37, 2674(1998) JAP, 83, 6771(1998) JAP, 88, 5904(2000)

  20. - Controllable Magnetochromatics - H = 50 Oe (d = 2.34 m) H = 100 Oe (d = 2.26 m) H = 200 Oe (d = 1.64 m)

  21. Under Parallel Magnetic Fields

  22. Under Parallel Magnetic Fields H = 200 Oe dH/dt = 100 Oe/s W = 10 μm L = 1.5 μm Ms = 17.6 emu/g td = 3 min Δx = 1.45 μm H x 10 m - Periodic one dimensional grating -

  23. 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

  24. We have well controlled and understood the ordered structures and the optical properties of the magnetic fluid thin films. Future Works Applications of Magnetic Fluids

  25. m m 10 10 m m Magnetic Field Dependent nMF(H) The nMF is increased under a higher field. The increase in nMF is suggested to be due to the column formation.

  26. Working Principle (a) H = 0, ncore > nMF, total reflection occurs IH=0 Magnetic fluid core cladding (b) H  0, ncore< nMF, total reflection vanishes IH0 IH0 < IH=0

  27. Modulation of Transmitted Light Intensity L = 796 m Ms = 0.61 emu/g H (Oe) Transmission loss (%) Transmission loss = (IT-IT,H=0)/IT,H=0

  28. - Experimental Setup H Transmission axis Transmission axis   He-Ne laser ( = 632.8 nm) w/0.01o resolution  Polarizer Ein Eout Sample Analyzer

  29. -H

  30. Summary The refractive index of magnetic fluid films can well manipulated. The feasibility of the magnetic-fluid-based optical modulator and switch is demonstrated.

  31. What else? • Conclusions Magnetically labeled immunoassay Photonic Crystal Switch CWDM Modulator Magnetic fluids

  32. Thank you for your attention!

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