By adding nanoparticles to silk, researchers have created a fabric that reflects 95 percent of sunlight. This keeps the material cool on a hot day.
About 15 percent of global electricity consumption goes to resources that keep us cool. So to reduce energy consumption, scientists are looking for ways to cool that don’t require electricity.
Materials scientists Jia Zhu of Nanjing University in China and Shanhui Fan of Stanford University in the United States set their sights on silk. They chose this fabric because it feels cool against the skin, reflecting most of the sunlight that hits it. This mainly concerns the infrared part, or heat radiation, and the visible part of the light. Silk also easily releases heat.
By adapting silk, the scientists were able to create a fabric that blocks even more sunlight: up to about 95 percent. They did this by encasing the fibers with nanoparticles of aluminum oxide. Due to this addition, the fabric also reflects the ultraviolet part of the sunlight.
When the researchers placed their side in sunlight, they saw that it remained 3.5 degrees cooler than its surroundings. It is the first substance to remain colder than the surrounding air in sunlight.
fake skin
The researchers also discovered that when they draped their silks over a surface that mimicked human skin, the fabric kept the ‘skin’ in the sun 8 degrees cooler than natural silk. Compared to cotton, the special silk was even 12.5 degrees cooler. The fake skin consisted of silicone rubber wrapped around a heater to mimic body heat.
As a final experiment, the researchers made a long-sleeved shirt from the modified silk. They asked a test subject to wear it on a sunny day with a temperature of 37 degrees Celsius. Using thermal cameras, the researchers proved that the shirt remained cool. When the test subject wore a shirt made of natural silk or cotton, these fabrics did warm up.
“So when you wear the artificial silk, you feel much cooler than when you wear normal textiles,” says Zhu. The special silk is comfortable, has good breathability and can be washed and dried repeatedly, Zhu says. According to him, the fabric is also inexpensive and can be produced on a large scale.