A soft and stretchable organic thermoelectric module has been created that can harvest energy from body heat. The breakthrough was enabled by a new composite material that may have widespread use in smart clothing, wearable electronics, and electronic skin.
The team combined three materials: the conducting polymer PEDOT:PSS, a water-soluble polyurethane rubber, and an ionic liquid. The result is a composite with unique properties. The PEDOT: PSS gives it thermoelectric properties, the rubber provides elasticity, and the ionic liquid ensures softness.
PEDOT:PSS is the most common conducting polymer and is used in many applications due to its good thermoelectric properties. But thick polymer film is too hard and brittle to be successfully integrated into wearable electronics. The new material is 100 times softer and 100 times more stretchable than PEDOT:PSS.
The ability to control the structure of the material both at the nanoscale and the microscale enabled the combination of properties of the different materials in a composite. The new composite is also printable. It was formulated by water-based solution blending and can be printed onto various surfaces. When the surface flexes or folds, the composite follows the motion. The process to manufacture the composite is inexpensive and environmentally friendly.
The researchers see a range of possibilities using the material to create soft and elastic organic conducting materials. Ionic liquids, conducting polymers, and traditional elastomers can be combined to produce new nanocomposites for many applications such as thermoelectric generators, supercapacitors, batteries, sensors, and in wearable and implantable applications that require thick, elastic, and electrically conducting materials.