Scientists create unique fabric for cool clothes

Chinese researchers at Stanford University have developed a plastic-based textile that can cool the human body and may someday reduce demand for air conditioning.

The material cools by not only taking away sweat like ordinary fabrics do but also by allowing the heat that the body emits as infrared radiation to pass through, which makes the wearers feel cooler than they would when wearing cotton clothes, according to the researchers' study, recently published in the journal Science.

By cooling the person rather than an entire building, a substantial impact could be made on global energy use, according to Yi Cui, an associate professor of materials science and engineering at Stanford and the lead author of the study.

The human body emits mid-infrared radiation, an invisible and benign wavelength of light. That contributes to more than 50 percent of the total body-heat loss in a typical indoor setting like an office.

However, traditional textiles are not designed for infrared radiation control.

To enhance radiative dissipation in hot weather, the researchers used nanoporous polyethylene, or nanoPE, a variant of polyethylene widely used in battery-making, which allows infrared radiation to pass through it while being opaque to visible light.

There are also other challenges that the researchers need to address beyond ensuring the cooling effect, such as wicking, mechanical strength and air permeability, which are important for a textile to be wearable.

The researchers altered nanoPE through a number of processes in order to make it into a suitable human cloth.

They first created microholes as thin as human hairs with commonly used microneedle punching, resembling the spacing between the yarns in woven cotton textiles.

Because the hole is so small, the visual opacity is not affected. The wicking rate and the mechanical strength of the new material also are comparable to cotton, according to the study.

To make the thin material more fabric-like, the researchers created a three-layer material with two sheets of treated polyethylene sandwiching a cotton mesh for strength and thickness.

They then tested the cooling effect of nanoPE with a device that simulated the heat output of skin. The material increases the simulated skin temperature less than cotton, they said.

Though the temperature difference is small, it can make a difference for air conditioning setpoints, the researchers said, which means someone dressed in the new material may not feel the need to turn on the air conditioner.