Researchers have created a smart material that can keep the wearer warm and cool with no energy input and can adapt to weather conditions outdoors and keep the wearer comfortable indoors, which could lead to a reduced need for heat or air conditioning.

A microstructured fiber (left) contains pores (right) that can be filled with a phase-changing material that absorbs and releases thermal energy. Source: ACS Applied Materials & Interface

The new material is made of silk and chitosan, material from the hard outer skeleton of shellfish, that is freeze spun into colored fibers with porous microstructures. The pores are filled with polyethylene glycol (PEG), a phase changing polymer that absorbs and releases thermal energy. The threads are coated with polydimethylsiloxane, which keeps the liquid PEG from leaking. This process resulted in strong fibers that are flexible and water repellent.

The team tested the fibers by weaving them into a patch of fabric and placed the patch in a polyester glove worn by a volunteer. The gloved hand was placed in a 122° F chamber. In this chamber, the solid PEG absorbed heat from the environment and melted into a liquid that cools the skin under the patch. The gloved hand then moved to a 50° F chamber. In the cold chamber, the PEG solidified and released heat and warmed the skin.

Smart textiles are not a new development but current smart materials cannot heat and cool the wearer. Also, they are often bulky, heavy, fragile, expensive and require an outside power source. According to the research team, the new smart material overcomes all of these challenges.

Researchers say that the process of creating this fabric is compatible with the existing textile industry. The next step is to research ways to scale up for mass production.

A paper on the new material was published in ACS Applied Materials and Interface.