The Cellulose Nanocrystal Electro-optic Effect

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The Cellulose Nanocrystal Electro-optic Effect

• Chad Teters, Wei Kong, Melissa Taylor, John
  Simonsen, Mike Lerner, Tom Plant, Glenn Evans
• Oregon State University
• Corvallis, Oregon

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PRESENTATION OVERVIEW

• Cellulose nanocrystals (CNXLs)
• Production
• Properties
• Transient electric birefringence (TEB)
• Alignment
• Optical effects
• Multi-order rotation
• Device fabrication
• issues

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Cellulose
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CELLULOSE NANOCRYSTAL PRODUCTION

• Native cellulose - Semi crystalline Polymer (70
  crystalline).

Amorphous portion
Crystalline portion
CONTROLLED ACID HYDROLYSIS
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TEM image of cellulose nanocrystals
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7 nm
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150 nm
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SOURCES OF CELLULOSE NANOCRYSTALS CELLULOSE
WHISKERSCELLULOSE NANOWHISKERSCELLULOSE
CRYSTALLITES
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Wood
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Sugar Beets
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Cotton
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Barnacles (tunicin)
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Bacterial Cellulose
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CELLULOSE BIOSYNTHESIS
R.M. Brown, 1996. J. Mat. Sci. Pure Appl.
Chem. A33(10) 1345-1373
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Slide from Wankei Wan, U. W. Ontario, London, ON,
Canada
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CELLULOSE NANOCRYSTALS
Beck-Candanedo, et. al. Biomacromol. (2005)
61048-1054
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Surface Area
m2/g
http//www.jm.com/engineered_products/filtration/
products/microfiber.pdf Winter, W.
presentation at ACS meeting, San Diego, March
2005 http//www.ipme.ru/e-journals/RAMS/no_5503
/staszczuk/staszczuk.pdf.
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MECHANICAL PROPERTIES

• Marks, Cell wall mechanics of tracheids 1967
• Sturcova, et al. (2005) Biomacromol. 6, 1055
• Yu, et al Science (2000) 287, 637

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OPTICS
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TRANSIENT ELECTRIC BIREFRINGENCE, AKA THE KERR
EFFECT

• Crossed polarizers typically emit no light
• Unless an optically active substance rotates the
  light
• Electric field can align birefringent substances
  and allow light to pass polarizers
• Kerr cells, Pokels cells used in fiber optics,
  lasers, confocal microscopy, etc.

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Original Kerr Cell 1875
Optically active medium glass
from Kelvin's Instruments and the Kelvin Museum
by G. Green and J. T. Lloyd
http//www.elec.gla.ac.uk/groups/opto/Kerr.html
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KERR CELL
http//www.photonics.com/dictionary/images/terms/k
errcell.gif
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SETUP
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BASIC DETECTION THEORY
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ALIGNMENT THEORY (STATIC FIELD)
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ALIGNMENT THEORY (STATIC FIELD)
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Alignment Theory (static field)
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ALIGNMENT THEORY (T-DEPENDENT FIELD)
Growth
Decay
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EMPIRICAL FIT
decay
rise
on
off
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ALIGNMENT THEORY (FITTING PARAMETERS)
fast
slow
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CNXL RESULTS (E FIELD DEPENDENCE)
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CNXL RESULTS (CONC. DEPENDENCE)
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KERR CELL COMPARISON
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CNXL RESULTS (MULTI-ORDER ROTATION)
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CNXL RESULTS (MULTI-ORDER ROTATION)
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CNXL RESULTS (MULTI-ORDER ROTATION)
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CNXL RESULTS (MULTI-ORDER ROTATION)
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CNXL RESULTS (MULTI-ORDER ROTATION)
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WAVE PLATE OPTICS
Kerr equation
G phase shift n refractive index d
pathlength ? wavelength
n refractive index K Kerr constant ?
wavelength E electric field strength
K f(concentration) K C Linearity is an
assumption
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APPLICATIONS

• Display devices
• Privacy glass
• Electrically variable waveplate for microscopy,
  general optics
• ???

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SCHEMATIC OF LIQUID CRYSTAL DISPLAY
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TRANSMITTANCE OF CNXL DISPERSION
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CNXL vs LCD
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CNXL CHALLENGES

• Colloid stability
• Conductivity, Joule heating
• Scattering
• Field direction in plane switching

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CONCLUSIONS

• Cellulose nanoparticle dispersions exhibit a
  strong electro-optic effect
• Effect dependent on square of field strength,
  concentration, path length, surface chemistry
• Device geometry requires in-plane switching
• CNXL dispersions hold the potential for
  electro-optic applications in a variety of fields
  and devices