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Stephen Chen

A research laboratory in the southern Chinese boomtown of Shenzhen has developed a kind of paint with qualities seemingly borrowed from the animal kingdom: it can change colours in the blink of eye.
Apart from other advantages, the newly developed technology could spare many couples from arguing over how to colourise their home. 
Imagine the fun of instantly changing the colour of everything, from the wall to the floor to the furniture, just by swiping a smartphone
Dr Du Xuemin
"Imagine a house that will cheer you up with a bright colour when it rains,” said Dr Du Xuemin, the lead scientist of the project.
“Imagine the fun of instantly changing the colour of everything, from the wall to the floor to the furniture, just by swiping a smartphone,” said Du, who works with the Shenzhen Institutes of Advanced Technology (SIAT) under the Chinese Academy of Science (CAS).
"Our paint will make all these dreams come true,” Du added.
The paint relies on nano-sized cells that can be controlled to inflate or deflate to deflect visible light at different wavelengths, thus generating different colours. 

In the core of each nano-cell is a kind of metal, for example copper. To reduce the size of the cell, a small current of electricity must be applied to give the metal a positive charge. This ultimately pulls the cell's crystalline shell inward. 
Another method sounds simpler: Just spray water over the painted wall and the ensuing chemical reaction will also change the size of the nano cells, Du said. 
The third way is even more natural: significant changes in the room temperature can also affect the colour of the paint, creating automatic seasonal palettes. 
In a paper recently published in the journal Sensors & Actuators B, Du's team demonstrated how to achieve rapid colour shifts by applying weak electric currents to the new material. 
They collaborated on this with researchers from the City University of Hong Kong and the Chinese University of Hong Kong.
They found that when natural light hit the nano cells, it was deflected by the uneven surface at various wavelengths, which resulted in the human eye seeing different colours. 

Unlike the liquid crystal screen of a mobile phone, the paint does not generate its own light. 
And unlike the reflective screens of electric readers like Amazon's Kindle, the new paint can generate numerous colours rather than just being black and white. 
Du said the biggest challenge of the technology was fabricating the extremely small cells, as the diameter of each one is only several hundredths the diameter of a typical human hair. 
The structure of the cell’s uneven surface and metallic core must also be controlled precisely, or it will not produce the correct or desired colours, the scientists added. 
But the team said they had solved most of the technical issues, and their laboratory can now produce a few dozen litres of the paint each day. 
"We are working with some companies in the chemicals industry to bring the technology from the lab to mass production,” said Du. 
“The idea of a paint that can change colour like a chameleon has generated enormous interest,” Du added. 
"When the product will be available to consumers for home decoration depends on many factors. In my conservative estimate, it will hit stores shelf within three years."


Till decorating do us part: Chinese team develops chameleon-like house paint that changes colour to keep the whole family happy

The colour of the paint can be changed in a variety of ways, such as by spraying water on it, firing weak electric currents at it, or just waiting for the room temperature to change significantly. Photo: SCMP Pictures

The paint is composed of many nano cells that can be inflated or deflated to deflect visible light at different wavelengths. Photo: SCMP Pictures

Hopefully, the new tech will put an end to family squabbles over at least one aspect of home decor. Photo: SCMP Pictures

Tech

Science & Research