In an article published in the journal Nature Nanotechnology, researchers detailed how, through a molecular bonding design strategy and scalable dip-coating methods, nanoprocessed silk can achieve a temperature of 3.5 degrees Celsius below ambient in the daytime.
This was due to the engineered silk’s ability to reflect most sunlight and radiate heat. The silk is said to be the first fabric developed that stays colder than the surrounding air when in sunlight.
The researchers–Jia Zhu at Nanjing University in China and Shanhui Fan at Stanford University and their colleagues–also found that when the silk was draped over a surface designed to simulate skin, it kept the surrogate 8 degrees cooler under direct sunlight than natural silk and 12.5 degrees cooler than cotton.
“We anticipate that this strategy of tailoring natural materials through convenient and scalable processes may not only provide a sustainable energy-saving approach to personal thermal management, but also inspire new pathways for the development of materials and devices for passive cooling to reduce energy consumption,” the researchers said.
The engineered silk was composed of fibers embedded with aluminum oxide nanoparticles that reflect the ultraviolet wavelengths of sunlight. In the final part of their experiments, they made a collared long-sleeved shirt from the engineered silk and asked a volunteer to wear it while standing out in the sun. Infrared images revealed that the shirt stayed cool. Similar infrared images captured of the volunteer wearing shirts made of natural silk or cotton showed that these fabrics warmed up.
The engineered silk is comfortable to wear, with good breathability, and can be washed and dried repeatedly without falling apart, researchers noted. The fabric is mainly designed to keep people cool when they are outdoors and exposed to sun, rather than in indoor settings like homes and office buildings.
Companies are invested in fabric cooling tech.
Forloh, a Made in America technical outdoor brand, recently introduced SolAir, a collection of apparel designed to keep wearers cool and comfortable when hiking, hunting, fishing or other outdoors activities.
The brand is introducing first-to-market brrr° Pro technology, with cooling minerals woven into fibers of the apparel that decrease body temperature 3.5 degrees. The warm-weather range features hyper-wicking and a 900+ UPF rating, along with anti-microbial and scent control.