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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!
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