Nanotechnology has brought another amazing breakthrough that will make us all more comfortable, will improve sporting performance, and possibly even save lives. By using a carbon nanotube coating, researchers from the University of Maryland have created a fabric that automatically regulates the garments cooling or insulating properties.

Current clothing is made of material that is either designed to keep marathon runners and people in hot climates cool, or mountain hikers and people in cold climates warm. But in these two different situations two different fabrics are needed.

Nanotechnology has now provided a fabric that can do both, by adjusting the way it reacts to the wearer’s temperature. As the cloth becomes moist from sweat in hot conditions, individual strands of fabric close up creating pores for heat to pass through. Additionally, and more importantly, the carbon nanotubes on the fibres react to the heat and moisture to allow infrared radiation to pass through.

As the wearer cools down, less sweat is produced and the fabric dries.  This causes the strands of yarn to spread out, and causes the nanotubes to repel infrared radiation, locking the heat in.

Before and after pictures of the same fibres, showing how the ‘gating’ of individual strands has opened pores in the fabric.

A video footage of the fibres expanding and contracting as a result of the carbon nanotube coating can be viewed here.

This new concept of expanding and contracting yarn fibres has been labelled ‘gating’ and has created a material that auto-regulates both cooling and insulating.

It is a concept that may revolutionise the clothing industry. As the study’s co-author, YuHuang Wang, a professor of chemistry and biochemistry at UMD, states, “This is the first technology that allows us to dynamically gate infrared radiation.”

His colleague, Min Ouyang, a professor of physics at UMD, agrees, “I think it's very exciting to be able to apply this gating phenomenon to the development of a textile that has the ability to improve the functionality of clothing and other fabrics.”

The researchers’ results have now been published in the journal Science, where they explain how their new fabric interacts with the human body and how (because of the carbon nanotube coating) the fibres interact with each other. They explain how, “The human body absorbs and loses heat largely through infrared radiation centering around a wavelength of 10 micrometres. However, neither our skin nor the textiles that make up clothing are capable of dynamically controlling this optical channel for thermal management. By coating triacetate-cellulose bimorph fibres with a thin layer of carbon nanotubes, we effectively modulated the infrared radiation by more than 35% as the relative humidity of the underlying skin changed.”

The online scientific journal Phys.org, further described the fabric, when it reported how, “The base yarn for this new textile is created with fibres made of two different synthetic materials—one absorbs water and the other repels it. The strands are coated with carbon nanotubes, a special class of lightweight, carbon-based, conductive metal.”

The carbon nanotubes are influenced by an electromagnetic coupling that changes as the distance between them changes. Because the fabric both repels and absorbs water, changes in humidity cause the strands to warp bringing the carbon nanotubes closer together or further apart.

The effect of this thermal management by carbon nanotubes is explained by Wang with an analogy which describes the discovery as follows; “You can think of this [electromagnetic] coupling effect like the bending of a radio antenna to change the wavelength or frequency it resonates with. It's a very simplified way to think of it, but imagine bringing two antennae close together to regulate the kind of electromagnetic wave they pick up. When the fibres are brought closer together, the radiation they interact with changes. In clothing, that means the fabric interacts with the heat radiating from the human body.”

Chemistry and Biochemistry Professor YuHuang Wang (left) and Physics Professor Min Ouyang.

While the clothing industry has yet to become involved, the development of the fabric is already winning plaudits from the scientific community. One such supporter is Prof. Ray Baughman, a chemist from University of Texas, who stated that, “This pioneering work provides an exciting new switchable characteristic for comfort-adjusting clothing.” Adding that, “Textiles were known that increase porosity in response to sweat or increasing temperature, as well as textiles that transmit the infrared radiation associated with body temperatures. However, no one before had found a way to switch both the porosity and infrared transparency of a textile so as to provide increased comfort in response to environmental conditions.”

While further work is needed before the fabric can be commercialized, the research duo do not expect any major problems in up-scaling. Both of the synthetic fabrics used are readily available, while the carbon coating can ‘easily be added during the standard drying process’.

This means that shops may soon be selling clothing that adjusts according to the wearer’s temperature. As a result, for the first time since clothing was first worn 170,000 years ago, people who are hot or cold do not need to react. They can let their clothes react for them.

As Ouyang observes, “The human body is a perfect radiator. It gives off heat quickly. For all of history, the only way to regulate the radiator has been to take clothes off or put clothes on. But this fabric is a true bi-directional regulator.”


Photo credit: Phys.org, UniversityofMaryland, & Science