A film coated with the novel thermoelectric ink. Photo: KTH Royal Institute of Technology.
A film coated with the novel thermoelectric ink. Photo: KTH Royal Institute of Technology.

Researchers in Sweden report that they are closing in on a way to replace the batteries in wearables and low-power applications for the internet of things (IoT). The answer lies in an ink coating that is able to convert low-grade heat, which is generated by all electrical devices, into electrical power.

In a paper in ACS Applied Materials & Interfaces, the researchers from KTH Royal Institute of Technology in Stockholm report their development of a promising thermoelectric coating for devices that generate heat up to 100°C.

Thermoelectricity is the direct conversion of heat to electricity. It’s possible to capture the heat that a device generates and convert it into power that can be used by the same device, or another device.

This requires specially designed thermoelectric materials. When one end of a thermoelectric material is heated up, charge carriers (negative electrons and positive ‘holes’ generated by the absence of electrons) move away from the hot end of the material towards the cold end, producing an electric current. One challenge is in managing the thermal conductivity and resistance in materials that can be applied to a large area without losing their performance over time.

Muhammet Toprak, professor of materials chemistry at KTH, says that the research his team performed focused on the design and development of hybrid thermoelectric materials for room-temperature operations. As part of this research, the team managed to integrate solid state semiconductors with flexible materials such as polymers to create a novel ink coating.

According to Toprak, the coating can be applied to any surface that dissipates heat, resulting in the generation of electrical power. This research also contributes to gaining a better understanding of the capabilities and limitations of compounds used for designing hybrid thermoelectric materials.

“These results open a new low-cost and sustainable way of producing and implementing thermoelectric coatings on a large scale,” Toprak says. “In the short term, this is expected to make an impact for IoT and other low power applications. It could replace batteries by being integrated as a coating in the form of wearable electronics.

“In the long run, with the use of more sustainable inorganic thermoelectric materials compositions and sustainable biopolymers such as cellulose and lignocellulose (or plant matter), the use of this technology on large areas will impact the adaptation of thermoelectric technology for efficient heat-to-power energy harvesting, as a complementary means to green transition.”

This story is adapted from material from KTH Royal Institute of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.