Chinese researchers use silk to develop humidity-responsive smart textile

People's expectations are increasing on what they wear: beautiful, cozy, and now, smart.

A new study published in the international journal Advanced Functional Materials says that scientists using silkworm silk have developed a smart textile that can automatically contract and stretch with humidity changes.

According to the study, the sleeves made from such smart textile can shrink as much as 45 percent in the vertical direction when exposed to moisture or sweat and then recover to its initial length when the environment becomes dry.

The key to the feature is a fiber artificial muscle developed by researchers from the Tianjin-based Nankai University.

The fiber artificial muscles refer to materials that mimic natural muscles and can reversibly contract, expand or rotate within one component due to an external stimulus, such as electricity, temperature, moisture and light.

In this study, the artificial muscle was made of silkworm silk because the natural fiber is cheap, comfortable and absorbs water well.

Liu Zunfeng, the lead researcher, said that the study was inspired by the mechanism of reversible volume expansion of silk fiber. After water molecules are absorbed by silk protein, the fiber volume would increase, and its porosity would change.

The fiber volume changes and structural transformation after water absorption and desorption will result in reversible contraction, expansion and rotation responses, indicating that silk would be a promising candidate for moisture-responsive smart textiles.

In addition, mature processing methods of silk, such as degumming, dyeing and thermal setting, ensure the extensive applicability of silk muscle.

The silk muscle can change porosity by adapting to sweat, rain, humidity and temperature.

"When you are sweating, you may find your clothes shrink. But after the sweat dries, the material will grow longer to keep you warm," said Liu.

Although researchers have not conducted experiments on humans, they believed that the clothing length changes would not bring any discomfort to the skin.

Liu said that the silk muscle would have broad prospects.

"Because silk is largely abundant and cost-effective, the silk muscle will open a path to more possibilities in textiles, medicine and soft robotics," he said.