1. Large Area Smart Windows for Indoor Light and Heat Modulation
Indrajit Mondal, A. K. Singh, S. Kiruthika and G. U. Kulkarni. Centre for Nano and Soft Matter Sciences, Bengaluru
Smart windows
Fabrication of Transparent Flexible Heater
Windows that change light transmission properties in response to heat, light or electricity to tune the amount of privacy, light and heat that enter into a space.
E.g.- Electro-chromic, Thermo-chromic, Thermo-tropic etc.
Opaque
Transparent
PET-sheet or Glass
Coating
Crackle
precursor
Metal deposition
& Lift-off
Crack template
Metal Mesh
Due to the growing awareness and demand for less energy consuming building, the glass panels are made smart with many functionalities which are not found in ordinary glass.
A Transparent Conducting Electrode ( TCE) or a Transparent Heater (TH) and an active material required for the fabrication of such smart glass.
Procedure: Spin coating crackle precursor on glass or PET substrate and self cracking followed by metal deposition and lift-off crackle precursor. °C 30 40 50 60 70 80 90
100 µm
1 cm
Wide spectral range
transmittance
Transparent flexible
heater
Seamless junctions
with high conductivity
Conventional TCE- ITO: Expensive, Brittle and chemically less stable.
Fabrication of Smart windows
Thermo-chromic Display
Thermochromic
Device
Hydrocarbon
Hydrogel
Metal Mesh
PET / Glass
carrying metal
mesh on top V I II
III
Translucent
VON
VOFF
Transparent
Opaque
Filled with Opaque
Filled with
transparent Hydrogel
Coated with opaque
thermochromic pigment
3.5 V
1 cm
VOFF
VON
Color and transparency change
with applied voltage
Fast Switching or response
After applying 5V voltage to different segments of display
Each segment of the 13-segment flexible display prepared with help of thermo-cromic pigment coated over transparent heater.
Further, power supply designed in such a way that it can have control over each segment. According to our choice we display numeric and alphabets on the display.
Active materials such as thermo-chromic pigment, hydro-carbon or hydro-gel are coated on the Transparent Heater.
A suitable power is supplied to change the color or transparency.
Hydrogel based Smart window
Hydrocarbon based smart window
VON
VOFF
Upon applying 5 V to this device, the hydrogel temperature increases (>40 °C) and the device becomes opaque because of its transition from a transparent liquid to an opaque gel state.
Upon applying 5V, the joule heat generated is transferred to the hydro-carbon layer within the device and it becomes transparent because of its transition.
VOFF
VON
Cyclic stability and
Transparency change
Advantages: (i) Low fabrication cost, (ii) Good flexibility, (iii) High mechanical and cyclic stability, (iv) Fast response and recovery.
Reference: A. K. Singh, S. Kiruthika, Indrajit Mondal and G. U. Kulkarni, J. Mater. Chem. C 2017, DOI: /c7tc01489a, -