Thermoelectric generators convert heat into electrical energy – temperature differences between the two sides of the generator generate a voltage and produce a current. Although not used as the main source of day-to-day power, they are used in specific applications, where they are invaluable. For example, they can be used to recover waste heat in power plants and factories (to improve efficiency), power space probes, and create wearable devices powered by body heat alone.

Challenges With Traditional Thermoelectric Materials

Traditionally used thermoelectric materials tend to be metal-based inorganic materials. These efficiently convert heat to electricity, but suffer from several limitations:

- Rigid structure – making them unsuitable for applications requiring flexibility, such as wearable devices.

- High cost.

- Complex manufacturing processes.

Organic thermoelectric materials have been suggested as an alternative, offering flexibility, non-toxicity, and a lower weight. However, these also face limitations, including low electrical conductivity and poor mechanical durability.

Flexible Thermoelectric Materials using CNTs

Researchers at the Korea Research Institute of Chemical Technology have recently made a breakthrough in producing a thermoelectric material that is flexible and has high conductivity. To achieve these, the researchers combined carbon nanotubes (CNTs) with Bi_0.45Sb_1.55Te₃ (bismuth-antimony-telluride/BST; a thermoelectric material), using a rapid solvent evaporation process to form a composite foam. The BST is distributed within the 3D CNT structure to create an electrically conductive network. Not only does this new material have a high thermoelectric performance – 5.7 times higher than  CNT foam alone – but it also has improved flexibility and durability, maintaining performance even after 10,000 bending tests.

Next-Gen Thermoelectric Generators

Current thermoelectric generators are limited either by a lack of flexibility or a lack of conductivity and durability. CNTs provide flexibility, durability, and conductivity, making them an ideal solution for the production of more effective thermoelectric generators. The moldable nature of the CNT-BST foam marks this material as a promising candidate for next-generation thermoelectric generators with exciting new applications, including battery-free wearable devices and waste heat recovery.

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Korea researchers develop flexible carbon nanotube thermoelectric generator