Sometimes it is too cold for us and then too warm again – annoying dressing-undressing of sweaters and co. Is therefore required. However, that may change: researchers have developed a sophisticated textile that can independently adapt its thermal properties to how hot, sweaty or cold the wearer is: the innovative fabric warms or cools as needed.

The human organism is like a radiator – we radiate heat. How much infrared radiation we emit into the environment can be regulated by clothing. In this context, material researchers have always developed sophisticated textiles in recent years. However, they can usually only be either or: Some materials insulate extremely well, thereby keeping the body warm. Others, on the other hand, can give off intense heat radiation to cool. A textile that can dynamically move from one function to another has not existed so far, say researchers around Yu Huang Wang of the University of Maryland at College Park. However, this ability should now possess their newly developed material.

Refined fibers with nano-coating

They report that the innovative fabric is made from specially assembled fibers coated with carbon nanotubes. The carrier material is composed of two different polymer materials which react in a contrary manner to moisture and heat with deformation. The dynamic properties of the material are based on this effect, explain the scientists: In moisture or heat, the fibers warp and thus change the structure of the material.

This process opens pores in the fabric that allow heat to escape, the researchers say. But the real highlight is the second effect: The structural change causes an electromagnetic coupling between the carbon nanotubes in the coating. This then leads to increased heat radiation of the material. In sweaty conditions, it thus ensures cooling. On the other hand, if the fabric is cold or dry, the opposite effect occurs: the pores close and the change in the electromagnetic coupling between the carbon nanotubes reduces the heat radiation. This gives the fabric an insulating effect.

“In simple terms, the concept is similar to the effects of radio antennas,” says Wang, “bending two antennas closer together changes their response to electromagnetic waves. The fibers in our material are similar: depending on how close or far they are brought together, their response to infrared radiation changes, “Wang said. At the level of the whole fabric this means that the material can emit more or less heat according to the conditions and thus keep the body warm or cool.

Literally cool clothes in planning

Concretely, the previous test results showed that the infrared-adapive material can change its heat radiation by more than 35 percent. As the researchers report, the fabric also appears to be well suited for use as a textile material with regard to further properties: the basic substances for producing the fibers are readily available and the carbon coating can be applied without problems. In addition, the fabric can be dyed and washed, the developers say.

Nevertheless, the substance has yet to be further optimized and tested until it can be incorporated into products, the scientists emphasize. However, they are confident that some day clothes will be based on their concept: “I find it very exciting to be able to use the material for the development of fabrics that can improve the functionality of garments and other fabrics,” says Co-author Min Ouyang.

Image Credit:  Faye Levine, University of Maryland

Thanks to Heinz V. Hoenen.  Follow him on twitter: @HeinzVHoenen