The concept of energy harvesting with flexible thermoelectrics shown with a schematic of aerosol jet printing. (Credit: Injung Lee)

The design and fabrication of single-wall carbon nanotube thermoelectric devices on flexible polyimide substrates can provide the basis for wearable energy converters.

Researchers used printed carbon nanotube networks to tackle challenges. For example, carbon nanotube spaghetti networks have much lower thermal conductivity than carbon nanotubes taken alone, due to the presence of junctions in the networks, which block heat flow. Also, direct printing such carbon nanotube networks can significantly reduce their cost when they are scaled up.

To eliminate hindrances to large-scale application of thermoelectric materials — toxicity, materials scarcity, mechanical brittleness — carbon nanotubes offer an excellent alternative to other commonly used materials.

The group’s approach demonstrates a path to using carbon nanotubes with printable electrodes on flexible polymer substrates in a process anticipated to be economical for large-volume manufacturing. It is also greener than other processes, because water is used as the solvent and additional dopants are avoided.