Hexagonal Patterns in Electronic Paper

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Hexagonal Patterns in Electronic Paper
T. Bert and H. De Smet TFCG Microsystems
ElintecGhent University - IMEC
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Overview
Introduction Pattern EHD Conclusion
Introduction ? what is electronic paper? ?
applications ? technology Pattern formation ?
properties ? conditions Electrohydrodynamics
? applications ? formulas
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Electronic Paper
Introduction Pattern EHD Conclusion
Benefits lightweightflexibilitybistabilityreadi
bility
Drawbacks switching speedno threshold
(electronic inks)no (good) colourelectrochemical
complexity
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Electronic Paper
Applications
Introduction Pattern EHD Conclusion
Bio-sensors
Smart Cards
E-Signs
E-Books
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Electrophoretic Image Display
Introduction Pattern EHD Conclusion
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Electrophoretic Image Display
Introduction Pattern EHD Conclusion
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Pattern formation
Introduction Pattern EHD Conclusion
Excess amount of free chargeHigh applied voltage
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Pattern formation
Introduction Pattern EHD Conclusion
Pattern properties ? Only for Vgt threshold value
10V? Hectic pigment movement stabilizes into
pattern? Time constant few seconds? Hexagon
Radius 600µ? Hexagon Radius independent of
V Bad optical properties ? electrode not
covered with pigment? net pigment movement is
slower
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Electrohydrodynamics
Introduction Pattern EHD Conclusion

• electrodynamics of moving media? electric forces
  on dielectric fluids - external force -
  interparticle force

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Electrohydrodynamics
Introduction Pattern EHD Conclusion
Hydrodynamics temperature difference
Electro-Hydrodynamics voltage difference
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Electrohydrodynamics
Introduction Pattern EHD Conclusion
Pattern formation Driving force ?
temperature difference ? voltage difference
(VdI) gt Damping force ? friction ?
viscosity
Far from equilibrium system organizes in
spatial or temporal structure e.g. hexagonal
patterns
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Electrohydrodynamics
Introduction Pattern EHD Conclusion
Parameters
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Electrohydrodynamics
Introduction Pattern EHD Conclusion
Numerical values
When Cgtgt1 ? critical T-value 100
? critical V-value 10V
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Conclusion
Introduction Pattern EHD Conclusion
Excess amount of charge
? Vcritical10V
? centrifugation and removal of micelles? Space
charge limit not reached? NO PATTERN
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Introduction Pattern EHD Conclusion
Thank you Questions?