07/01/2013 1 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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Laminated electro-active foils for the built environment Area Electr… · Electro-optic bi-stability in SmA LC materials Schematic of SmA liquid crystals AC low frequncy (~50Hz;
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07/01/2013
1
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
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.