In this blog post, we will look at how smart glass works and its various applications, and see how it is a technology that goes beyond simple windows to lead to energy savings and space innovation.
One of the most pressing issues of the 21st century is the serious energy shortage. Despite this, it is common to see people sitting by windows with curtains or blinds closed to block out the strong sunlight, and lights turned on even during the day to brighten up the darkened room, which is a waste of energy. What is the solution to this energy waste problem? Smart glass may be the answer. Smart materials are materials that can respond to changes in the external environment, and smart glass, which changes color and becomes transparent depending on the electric current, is a representative example. Among them, variable transmittance glass and ultraviolet-reflective glass are the most common.
Based on the principle of adjusting the light transmittance and reflectance as desired, variable transmittance glass can freely control the brightness of a room without curtains or blinds, which is very helpful for saving energy. Normally, variable transmittance glass is dark blue, but it becomes transparent in less than a second when electricity is applied. Therefore, the higher the voltage applied with the switch, the more transparent the glass becomes. In other words, you can freely change the visible light transmittance of the glass by turning the switch.
On the other hand, infrared-reflective glass, which is a type of smart glass coated with a thin layer of silver, is transparent but blocks infrared rays. Thanks to this characteristic, it not only blocks heat rays in the hot summer, but also reflects heat rays from heating back into the room in the cold winter, creating a warming effect.
Smart glass can be used in many ways in our daily lives. Variable transmittance glass can be used in buildings, train windows, car sunroofs, rearview mirrors, sunglasses, and more. And when you need some privacy, transparent glass can be used as an interior partition to block the view from the outside. When opaque, it can also be used as a high-resolution screen for projectors and computers.
What is the secret behind this ability to become transparent and opaque? The answer lies in the film between the two layers of glass. Between the two films are tiny blue polarizing particles suspended in liquid droplets. Normally, the particles move irregularly, absorbing light and appearing dark blue. However, when electricity is passed through both films to allow light to pass through, the polarized particles align with the electric field, and the glass becomes transparent. Smart glass, which uses electricity to control transparency, appears transparent under normal conditions and can be used as a blind by changing color automatically when necessary. In addition, there is glass that blocks near-infrared rays, which generate heat from sunlight, by coating the glass with fine metal particles instead of electricity. As a result, only light that helps brighten the room enters the room.
A research team led by Dr. Ryoji Akashi of Fuji Xerox in Japan announced in the latest issue of Advanced Materials, a journal specializing in materials engineering, that they have created contractile pigment sacs similar to those found in the skin of squid and octopus using a polymer material called NIPAM. The cross-linked polymer material becomes a soft gel that changes with temperature, allowing it to change color. For example, at normal room temperature, the gel expands, causing the pigment sacs to enlarge and turn black, but when heated to 40°C, the gel shrinks and becomes transparent. Applying this principle, the team created smart glass that can change color in response to temperature changes by placing the gel between glass panes. Smart polymer materials currently under development can respond not only to temperature changes but also to acidity, electric currents, and the presence of chemicals.
We have looked at the principles and advantages of smart glass. Energy resources are limited, so energy collection and storage technologies are being actively researched to find solutions to this problem. Smart glass, which can control light transmittance in an efficient and economical manner, is attracting a lot of attention as a functional solution. With interest from various fields, smart glass is expected to become an essential part of human civilization in the 21st century.
