Ink Provides Thermoelectric Power for IoT Devices

The IoT is very much at the heart of our lives today. Whether it is a smart watch measuring our body functions, or monitoring the performance and condition of machines in an industrial installation, the IoT has helped to make our lives safer and more predictable. To be able to perform these functions requires many sensors, which are situated in areas that are often hard to access. These sensors require power to take measurements and transmit them back to a router. It is also becoming more and more common that the sensors are part of a cluster, where calculations can be performed close to where they are needed, at the edge of the system. In that case, even more power is required. Because of their location, and often their design, these sensors and sensor clusters cannot be connected to mains power and rely on batteries, which even then are hard to access to replace or charge. Energy harvesting has become a popular method of topping up the charge in the batteries, or in some cases to completely power the devices themselves. Capturing energy from the sun, vibration or heat and converting it to electrical energy to power the devices requires more components, which consume power themselves, add cost to the end product and make the devices larger than they could be. However, researchers in Sweden are working on a different method of scavenging energy that has none of those disadvantages.

The researchers are looking to develop an ink coating that enables low-grade heat, which is generated by the devices themselves, to be converted to electrical power. In a new paper that has been publishing in American Chemical Society Applied Materials & Interfaces, the researchers from KTH Royal Institute of Technology in Stockholm report that they have developed a promising blend of thermoelectric coating for devices that generate heat amounting to less than 100 ^oC. The new ink will capture the heat that a device generates and convert to power that can be used by the same device, or another device.

What are required are specially-designed thermoelectric materials. When one end of a thermoelectric material is heated up, charge carriers (electrons and holes) move away from the hot end towards the cold end, resulting in an electric current. One challenge is in managing the thermal conductivity and resistance with 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, which integrates solid state semiconductors with flexible materials such as polymers, to formulate inks. The coating can be applied to any surface that dissipates heat, to generate electrical power. The research also makes headway in gaining better understanding of the capabilities and limitations of materials used for hybrid thermoelectric material design. “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.

The work was performed in collaboration with University of Valencia, Spain, and University of Warwick, UK.