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Daping Chu

Department of Engineering University of Cambridge

CIKC Showcase, 18 Dec 2012

Photonics and Sensors Group

Laminated electro-active foils

for the built environment

Acknowledgements

Photonics and Sensors Group:

Bill Crossland, Tony Davey, Mike Pivnenko, Huan Xu, Andriy Dyadusha, John Moore,

Stuart Speakman, Giovanni Orlando, Kun Li, Ivonne Median

Industrial collaborators: (TSB PICWIN Project)

Dow Corning, Vector Foiltech, SODA, DuPont Teijin Films, PETEC, Timsons

Financial supports:

EPSRC/CIKC PLACORD, LEAF and SAPLING Projects

TSB PICWIN Project

CAPE SiLC, SunSiLC-1/2/3 and other Projects

EPSRC Platform Grant (Liquid Crystal Photonics)

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Synopsis

» The need of radiation control for Green Buildings

Energy consumption in the built environment

Two examples (London City Hall and Water Cube)

» SmA liquid crystal material and dynamic scattering

» From laboratory to industry

The need for a sustainable built environment

Built environment in UK:

• Energy consumption 33% of the total; ( space heating, cooling, lighting)

• Building materials ~30% of all new materials;

• Emission 40% of the total.

Need for radiation control – even 1 degree can make a difference!

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Synopsis

» The need of radiation control for Green Buildings

» SmA liquid crystal material and dynamic scattering

Smectic A liquid crystals

Dynamic scattering

Electro-optical properties

Materials for high stability dyes and UV durable colourants

Performance of solar control

» From laboratory to industry

Liquid crystals

Typical liquid crystal molecules

Methoxybenzilidene Butylanaline (“MBBA”)

p-decyloxybenzylidene p'-amino 2-methylbutylcinnamate ("DOBAMBC")

A Chemist’s view:

A Physicist’s view:

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Some of liquid crystal phases

Isotropic Nematic Smectic A

Electro-optic bi-stability in SmA LC materials

Schematic of SmA liquid crystals

AC low frequncy (~50Hz; >60V RMS)

Clear State LC

AC high frequncy (1K – 2KHz; >60V RMS)

Scattered State LC

Permanently stable with no voltage applied.

Permanently stable with no voltage applied.

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Organic SmA LCs and ionic dopants

N

8CB (4-cyano-4’-octylbiphenyl). K 21.5 ∘C SA 32.5 ∘C N 40.0 ∘C I. Relative Permittivity: ell = 11.9 e⟘ = 4.7, De = 7.2 [14].

Packing of the molecules into smectic layers is promoted by the presence of the long axial alkyl chains as well as by the dispersive interactions between the conjugated cores of these molecules and dipole-dipole interactions due to the terminal polar cyanonitrile groups.

8CB

Dynamic scattering in SmA LCs

Most smectic A liquid crystals have a positive dielectric anisotropy but a negative conductivity anisotropy.

Smectic dynamic scattering is preceded by Helfrich-Hurault undulations caused by the space charge.

Proposed threshold Equations:

4 6 8 10 12 14 16 18 20 22 24 26

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Th

resh

old

Vo

lta

ge

, V

(rm

s)

Cell Thickness, m

Vc-2nd-test

Vs-2nd-test

Vc-1st-test

Vs-1st-test

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Dynamic scattering in nematic LCs

Ez

Ex (Eε,x)

b) Schematic of William Domain.

a) Schematic of bend fluctuation and charge segregation.

c) Periodical pattern of circular motions in the dynamic scattering state.

Molecules

Motion directions of

molecules due to

convective instability

x

Φ

~V

~V

-V

+V

Space charge formation in planar aligned nematic

(opposed by bend elastic constant)

Molecular motion torque is in the Z-direction & opposes the diectric torque zx

zx

EE

EE

)1(

)1(

//

,

//

Materials for high stability dyes

Customised anthraquinone-based black dye mixture.

20 million switching operations demonstrated.

Next generation dyes are under test.

Patent application filed

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UV durable colourants

• In-house made outdoor UV tester. • Cover glass > 92% transmission at 320-340 nm. • Set on the roof of the CAPE building. • 45-degree tiled towards south for maximum

radiation of sunlight. Test results:

• 97 days (20/7-25/10/2010). • Narrow sides were covered. • Later acceleration test was used.

Final UV lifetime test > 7 years.

Patent application filed

Synopsis

» The need of radiation control for Green Buildings

» SmA liquid crystal material and dynamic scattering

» From laboratory to industry

Glass cells

Laminated plastic cells

Graphene transparent electrodes

Small window demonstrators

PICWIN demonstrators

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Grey scales and colours

Night view

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Laminated electro-active foil (LEAF)

To develop a technology for a plastic envelope liquid crystal display.

One of the first laminated cells

Laminated smectic A cells

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Small window demonstrator: Single pixel

Small window demonstrator: Single pixel

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PICWIN demonstrator: Sheets

Laminated foils for TSB PICWIN project

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PICWIN demonstrator: Construction units

Thank you!