Electric wristband heaters for constant portable warmth

Lightweight wearable heaters with heating elements embedded within the fabric could help keep people warm, but previous attempts have resulted in hot stiff wires or threads that cannot be safely washed.

Recently, researchers have treated fabric and yarn with poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate). This flexible coating warmed up the materials and stayed in place after washing.

The polymers were not conductive enough for personal heating.

So, the researchers dipped the polymer-coated cotton yarn into ethylene glycol, which is not irritating to human skin.

When they applied voltage to the material, it warmed up, requiring lower voltages to reach high temperatures than some previously reported flexible heaters.

Finally, the researchers sewed multiple pieces of the yarn into a "TU" pattern on a bit of fabric with an additional fabric backing. When the heater was connected to a three-volt power supply and attached to a person's wrist, the heat distribution in the thermal wristband was steady as it was bent back and forth. The researchers say the wristband can also be powered by a battery via an external circuit for more portability.