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Particle-based display technologies. Ian Morrison Cabot Corporation. Particle based displays. Reflective not emissive “Adjusts” with ambient light Thin, flexible, low power? The electronics is a real challenge.

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Particle based display technologies l.jpg

Particle-based display technologies

Ian Morrison

Cabot Corporation

ACS Summer School on Nanoparticle Materials


Particle based displays l.jpg
Particle based displays

  • Reflective not emissive

  • “Adjusts” with ambient light

  • Thin, flexible, low power?

  • The electronics is a real challenge.

  • Require high resistivity so particles move, not ions therefore – nonaqueous dispersions

ACS Summer School on Nanoparticle Materials


To create a display start with a print l.jpg
To create a display – start with a print

and invent ways to make it change:

ACS Summer School on Nanoparticle Materials


The gyricon display l.jpg
The Gyricon Display

ACS Summer School on Nanoparticle Materials


Gyricon ball dynamics l.jpg

Ground Electrode

E

Fluid Filled Cavity

q+

X

Bichromal Ball

q

d

Switching Electrode

Z

Y

Gyricon ball dynamics*

(*Rick Lean, MIT)

Un-damped

Under-damped

Critical-damped

Over-damped

ACS Summer School on Nanoparticle Materials


Suspended particle displays l.jpg
Suspended particle displays*

*Invented by E.H. Land in 1934

ACS Summer School on Nanoparticle Materials


Electrophoretic displays l.jpg
Electrophoretic displays

ACS Summer School on Nanoparticle Materials


Problems with particle displays l.jpg
Problems with particle displays

Sedimentation:

Electrohydrodynamics:

ACS Summer School on Nanoparticle Materials


A solution encapsulation l.jpg
A solution - encapsulation

Light State

Dark State

  • “Solves”

    • Particle setting

    • Electrohydrodynamic effects

  • “Creates”

    • Self-spacing electrodes

    • “Coatable” displays

NOTE: These capsules are ~ 100 microns in diameter.

ACS Summer School on Nanoparticle Materials


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Shutter mode

ACS Summer School on Nanoparticle Materials


Switching speed use two different pigments l.jpg
Switching speed? – use two different pigments

  • Switching time goes as square of thickness:

  • The necessary thickness is determined by the optical density.

  • Dye solutions have much lower optical density than pigments.

  • Therefore dual pigments enables thinner.

ACS Summer School on Nanoparticle Materials


Dual particle displays l.jpg
Dual particle displays

Sony’s LIBRie EBR-1000EP from E Ink and Phillips Electronics

ACS Summer School on Nanoparticle Materials


Dual particle displays13 l.jpg
Dual particle displays

ACS Summer School on Nanoparticle Materials


Dispersions of oppositely charged particles l.jpg
Dispersions of oppositely charged particles

ACS Summer School on Nanoparticle Materials


How to image with flocculated particles l.jpg
How to image with flocculated particles

The field necessary to separate charged particles is:

n.b. The force varies with the product of particle charges, but the field also varies with the difference.

Practical considerations set an upper limit of about 0.5 V/mm.

A steric barrier is necessary to limit the maximum attractive force.

ACS Summer School on Nanoparticle Materials


Steric barrier necessary for typical pigments in oil l.jpg
Steric barrier necessary for typical pigments in oil

For particle radii of 150 nm, zeta potentials of +52 mV and –52 mV (corresponding to 12 charges per particle!), the background conductivity of 50 pS/cm, and a Hamaker constant of 4.05x10-20 J.

ACS Summer School on Nanoparticle Materials


Control of interparticle spacing l.jpg

Control of interparticle spacing

Electrostatic and dispersion forces are short range compared to the applied electric field.

Therefore we produce particles that only move above a limiting electric field – an electric yield point.

Manipulating the steric barriers and uneven surface charges controls the “yield” point.

This enables simple threshold addressing – “line-by-line”.

ACS Summer School on Nanoparticle Materials


Threshold addressing by other means l.jpg
Threshold addressing by other means

  • From the physics of colloids:

    • “Inverse” electrorheological fluids

    • Field dependence of zeta potential

    • AC electric fields – time dependencies

    • Particle-particle or particle-wall adhesion

    • Structures in fluid (particles or wide variety of polymer gels)

ACS Summer School on Nanoparticle Materials


What about color l.jpg
What about color?

Color filter arrays

Simple, but 2/3rds loss in brightness.

ACS Summer School on Nanoparticle Materials


Photoelectrophoretic displays l.jpg
Photoelectrophoretic displays

  • Photosensitive pigments

  • Light + electric field produces change in charge

  • Particles migrate in the field – in or out of view

  • Also a passive addressing scheme

ACS Summer School on Nanoparticle Materials


Color via plasmon resonance l.jpg
Color via plasmon resonance

The magnitude, peak wavelength, and spectral bandwidth of the plasmon resonance associated with a nanoparticle are dependent on the particle’s size, shape, and material composition, as well as the local environment.

Silver nanoparticles

Au and thin gold layers on silica.

http://www.ece.rice.edu/~halas/

http://physics.ucsd.edu/~drs/plasmon_research_home.htm#what

ACS Summer School on Nanoparticle Materials


Plasmon resonance color depends on interparticle distance l.jpg
Plasmon resonance – color depends on interparticle distance

Three color states when viewed from the top, depending on the electric field.

Blue

Red

Black

ACS Summer School on Nanoparticle Materials


Control of spacing with tethers l.jpg
Control of spacing with tethers distance

Polymer tethers keep particles within 10’s of nanometers – switching times are very short.

On

Off

ACS Summer School on Nanoparticle Materials


Quantum effects l.jpg
Quantum effects distance

Colloidal CdSe quantum dots dispersed in hexane. Quantum confinement effects allow quantum-dot color to be tuned with particle size. (Fluorescence shown.)

Moungi Bawendi

http://web.mit.edu/chemistry/nanocluster/

ACS Summer School on Nanoparticle Materials


Q dot optics also depend on interparticle distance l.jpg
Q-dot optics also depend on interparticle distance distance

  • Large Q-dots quench smaller Q-dots

  • Q-dots can be coated with a dielectric and charged

  • Q-dots could be tethered to each other or to an electrode.

ACS Summer School on Nanoparticle Materials


Electron injection into quantum dots l.jpg
Electron injection into quantum dots distance

n.b. One electron per particle makes these 103 to 104 more sensitive than molecular electrochromics.

http://dcwww.epfl.ch/lpi/electr.html

ACS Summer School on Nanoparticle Materials


Quantum dot electrochromic display l.jpg
Quantum dot electrochromic display distance

Electrode

Q Dot Layer

Dielectric layer

ITO on PE

ACS Summer School on Nanoparticle Materials


Slide28 l.jpg

Cabot – We make fine particles by the ton. distance

www.cabot-corp.com

ACS Summer School on Nanoparticle Materials