This article is from WeChat official account: science home (ID: steamforkids) , Author: Seven Jun, from the title figure: Vision China < /span>

Recently, a short video went viral on the Internet and received 3.4 million views.

Let’s take a look first–

It turns out thatwhen a light rail train passes through a residential area, the window glass will automatically change color to shield the content of the residential area and protect the privacy of residents. Netizens praised this meticulous and considerate design.

But how is this done?

In fact, this light rail is Singapore’s Bukit Panjang light rail. Bukit Panjang Light Rail started operation on November 6, 1999. All trains on this line, except for the windshield at the front of the train, can automatically shut down within 6 meters of the residential area of ​​the government HDB.

In order not to disturb the people, Bukit Pan made the tires of the light rail still made of rubber, which makes the noise less. Except to makeIn addition to using smart glass and noise-reducing rubber tires, this model of train is also Singapore’s first unmanned train.

The glass that can actively gelatinize is called smart glass. Smart glass is also used in public toilets in Yoyogishincho Park in Tokyo’s Shibuya District, which caused much controversy some time ago. However, Bukit Pan makes the history of the light rail longer and is also one of the first public facilities in the world to try smart glass.

Smart glass public toilets in Yoyogisukamachi Park in Shibuya District, Tokyo

There are many types of smart glass. Singapore’s Bukit Panjang light rail uses electrochromic glass, an earlier variety of smart glass.

Electrochromic smart glass uses electrochromic materials. The electrochromic effect was discovered as early as the 19th century, but this phenomenon was not fully understood until the 1960s.

In simple terms, voltage can cause the electrochromic material to undergo oxidation or reduction reactions, and the light band absorbed by the reacted material will also change. This is the origin of electrochromism.

The beautiful color of electrochromic materials. Image source: georgia tech

Many substances have electrochromic properties, such as some metal oxides (such as nickel oxide), Prussian blue, viologen, etc.

The name Violet essence is very strange. It is a kind of organic matter, and it is characterized by two rings.