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Smart Glass Developed at NTHU
Glass has just gotten smarter. A research team led by Prof. Tai Nyan-hwa of the Department of Materials Science and Engineering has recently used graphene to develop a type of heat-sensitive glass that becomes opaque when it reaches a certain temperature. While its primary application is for automobiles, where it can reduce internal heat, thereby saving energy and reducing the possibility of heat exhaustion or death of infants accidentally left inside on a hot day, it can also be used to help cool buildings. Tai is now applying to have his award-winning smart glass patented in several countries.
 
The concept of graphene smart glass was first conceived and developed several years ago by Tai and his doctoral student Chou Hung-Tao.
 
Tai said that graphene (GO) is able to transform optical energy into thermal energy, so that when it’s mixed with a temperature-sensitive hydrogel it turns into a liquid substance which can be injected between two pieces of glass, and when the ambient temperature goes above 32°C, in 1 to 2 minutes the smart glass turn opaque, blocking most of the light. Used as automobile windows, once the air conditioning is turned on, the glass will resume full transparency after cooling. By adjusting the formula, the glass can turn different colors and be used to meet different needs.
 
"Look, just a bit of strong light and the glass changes color!" says Tai, pointing towards a LEGO house made by his students, half of which is fitted with ordinary glass, and the other half with graphene smart glass. After applying the strong light for five minutes at room temperature, the side with the graphene roof is 34°C inside, while the other side has soared to 44°C.
 
Developed by Tai’s research team working at NTHU’s Advanced Carbon Nano-materials (ACNM) laboratory, the smart glass won third place in this year’s Green Tech Contest held by the TECO Technology Foundation. The team consists of doctoral student Hsiao Chung-Hsuan, and master’s students Hung Ya-Min, Chien Ming-Shen, Tsai Meng-Ting, and Li Ming-Yao.
 
In this age of global warming, with temperatures regularly topping 50 degrees Celsius, Tai’s heat-reducing and energy-saving smart glass is already receiving lots of interest.
 
Graphene smart glass may appear similar to the lenses used in photochromic sunglasses, but the principle is completely different. As team member Li Mingyao explains, the photochromic lenses used in sunglasses have silver chloride or halide coated on the surface or inside, which undergoes a chemical reaction in UV light, resulting in a darkening of the glass. By contrast, smart glass uses a temperature-sensitive polymer, thus reducing the cost while also allowing the use of different colors.
 
Li says that the most difficult part of making smart glass is that bubbles tend to form when the liquid substance is injected into the glass, but this problem can be solved in the mass production process.
 
Comparison between graphene smart glass and the photochromic lenses used in sunglasses
 
 
Smart glass
Photochromic lenses
Principle
Graphene is able to transform optical energy into thermal energy; when mixed with a temperature-sensitive hydrogel, light causes it to block both light and heat.
Photochromic lenses have silver chloride or halide coated on the surface or inside, which undergoes a chemical reaction in UV light, resulting in a darkening of the glass.
Speed of change
1–2 minutes
30 seconds
Cost
Low
High
Colors
Multiple
Single
 
Professor Tai Nyan-hwa of the Department of Materials Science and Engineering with his research team.

Professor Tai Nyan-hwa of the Department of Materials Science and Engineering with his research team.

Testing the heat-reducing ability of graphene smart glass.

Testing the heat-reducing ability of graphene smart glass.

Members of the research team working on the LEGO house fitted with ordinary glass and graphene smart glass.

Members of the research team working on the LEGO house fitted with ordinary glass and graphene smart glass.

After receiving two minutes of intense light, the ordinary glass (left) remains transparent, while the graphene smart glass has turned opaque.

After receiving two minutes of intense light, the ordinary glass (left) remains transparent, while the graphene smart glass has turned opaque.

 

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