Smart glass is an innovative solution for energy conservation that can adjust its transparency and color in response to changes in electric current or temperature. It can be used in buildings, cars, sunglasses, and more, and contributes to increasing energy efficiency and improving indoor environments.
One of the most talked-about issues of the 21st century is the severe energy shortage, yet it is not uncommon to see the energy-wasting phenomenon of people sitting by the window turning on the lights all the time, even during the day, to illuminate a room that has been darkened by the strong sunlight due to closed curtains or blinds. What is the solution to this energy-wasting problem? Smart glass could be the answer. Smart materials are materials that can respond to changes in the external environment, and smart glass, which can change color and become transparent depending on the electric current, is a typical example. Among them, transparent glass and UV reflective glass are the most common.
Thanks to the principle of adjusting the transmission or reflection of light, tinted glass is a great way to save energy because it allows you to control the brightness of a room without the need for curtains or blinds. Normally, tinted glass is a dark blue color, but when it is electrified, it becomes transparent in less than a second. The higher the voltage applied by the switch, the more transparent the glass becomes. This means that you can freely change the visible light transmission of the glass by flipping the switch.
On the other hand, infrared reflective glass, a type of smart glass with a thin silver coating, is transparent but also blocks infrared light. Thanks to these properties, it can not only block heat rays in hot summers, but also harness the heat from heating in cold winters and reflect it back into the room to keep it warm.
Smart glass has many uses in our daily lives. It can be used for windows in buildings and trains, sunroofs and rearview mirrors in cars, sunglasses, and more. And if you need privacy, transparent glass can be used as a room divider that makes it impossible to see inside. In its opaque state, it can also be used as a high-resolution screen for projectors, videos, and computers.
But what’s the secret behind the transparency and opacity? The answer is hidden in the film between the glass and the glass. Between the two sheets of film are microscopic blue light-polarizing particles in a liquid droplet. Normally, the particles are in irregular motion, so they absorb light and show a deep blue color. However, when electricity is passed through both films to allow light to pass through, the light-polarizing particles become parallel to the electric field and the glass becomes transparent. Smart glass that controls its transparency with electricity looks transparent at all times and changes color spontaneously when needed, creating a blind effect. In addition to electricity, there are also glasses that are coated with microscopic metal particles that block the near-infrared rays that heat up sunlight. So the only light that enters the room is the light that helps to brighten it.
In the latest issue of Advanced Materials, a materials engineering journal, Dr. Ryojiro Akashi and his team at Fuji Xerox Corporation in Japan report that they have created contractile pigment pockets, like those found in the skin of squid and octopus, from a polymer called NIPAM. The cross-linked polymer forms a soft gel and changes color with changes in temperature, which can be harnessed to change color. For example, at normal room temperature, the gel expands, making the pigment pockets black as they enlarge, but when heated to 40°C, the gel contracts and becomes transparent. This principle has been applied to create smart glass that can change color as the temperature changes by putting the gel between the panes of glass. The trend of smart polymers that are being developed can respond not only to temperature changes, but also to acidity, electricity, and the presence of chemicals.
So far, we have seen the principles and advantages of smart glass. As energy resources are finite, energy collection and energy storage technologies are being actively researched to counteract this. Smart glass, which can regulate light transmittance in an efficient and economical way, has received a lot of attention as a functional countermeasure. Thanks to the interest from various fields, smart glass is expected to become a necessity for human civilization in the 21st century.
