Thermoelectric effect between two liquid materials observed for the first time

A trio of physicists at Sorbonne University in France have observed for the first time a thermoelectric effect between two liquid materials. In their research, published in Proceedings of the National Academy of SciencesMarlone Vernet, Stephan Fauve and Christophe Gissinger brought two types of liquid metals together at room temperature and subjected them to a heat gradient.

Scientists have known for years that thermoelectric devices can convert thermal energy into electricity and vice versa. Such thermoelectric effects have been observed at the interfaces between two solids and between solids and liquids, but so far never between two liquids. In this new effort, the researchers built an environment conducive to such an event and tested it in their laboratory.

The environment consisted of a cylinder with a smaller cylinder in the middle. The researchers poured liquid mercury into the outer cylinder and then poured liquid gallium on top. The gallium floated because it was lighter. They then added a cooling device to cool the outer walls of the outer cylinder and a heating device to heat the walls of the inner cylinder.

This resulted in a temperature gradient between the two metals. The team then inserted a wire into the outer cylinder where the two metals met; the other end was connected to an electricity measuring device.

The researchers found that the addition of a temperature gradient led to a thermoelectric effect at the interface between the two liquid metals. They also found that it was turbulent: the flow flowed in a loop from the hot part of the cylinder to the cold part. Further testing showed that there were multiple loops. They also found spots in the interface where no electricity was generated, which doesn’t happen with thermoelectric effects between solids, they noted.

The researchers suggest that the reason such thermoelectric effects have not been observed before is because no one was looking for them. They also note that their findings could have implications for new types of battery development.