A Jacket That Breaths: Thins Out with Sweat to Prevent Overheating

If you think you’ll be wearing your jacket indefinitely once the sunshine fades, a material that decreases in thickness when you sweat could be a game changer.

Researchers have previously created self-adaptive materials that help cool individuals in high temperatures by emitting excess heat as infrared radiation. However, these materials generally operate in only one direction and are not effective for retaining warmth in cooler environments.

Xiuqiang Li, a Chinese astronaut, along with his team, has crafted a jacket that consists of layers that dry and flatten when wet. This unique property allows the jacket to become thicker in cooler surroundings and thinner in warmer conditions, primarily due to human perspiration. “The amount of sweat produced serves as a timely and straightforward indicator of the body’s actual thermal needs,” notes Li.

The design of the clothing resembles that of standard down jackets but incorporates layers of cellulose derived from bacteria. This is further bolstered with polyester to ensure that the fabric’s outer layer can expand effectively. Li’s team discovered that the cellulose layer does not dry in a predictable manner and remains fixed at a certain angle for up to 12 hours, working effectively after 200 cycles of transitioning from flat to curved.

The team examined how much heat the material emitted while being worn under varying moisture levels. They found it to feel as cool as standard polyester shirts when wet, yet nearly as warm as down jackets when in a similar condition.

These assessments were akin to wearing the material directly against bare skin. “Theoretically, when the material is layered over other clothing items, such as t-shirts, the sweat produced can permeate through these inner layers, potentially triggering a response that causes thinning,” states Xiaofeng Jiang, who is also from Nanjing Aviation University.

With these insights, the team aims to enhance the fibers to ensure they generate enough warmth to be worn without additional layers.

Li believes that scaling up the production of these materials should be feasible, as bacterial cellulose is readily obtainable and cost-effective; however, the team must first confirm that it can withstand the durability expected from conventional clothing.