Achieving thermal rectification in designed liquid-liquid systems

Thermal rectification is generally implemented using solid structures. We demonstrate how thermal transport can be rectified using designed liquid-liquid structures consisting of thin adjacent immiscible water and hexane layers. For specified hot and cold side temperatures, the heat flux differs when either water or hexane is placed on the hot side, demonstrating thermal rectification between the two cases. The rectification is influenced by the relative thicknesses of the layers. It is the highest when the water-hexane interface temperatures for both cases are identical. Changing the thermal conductivity of hexane, which is the lower thermal conductivity liquid, e.g., by potentially loading it with conducting or insulating nanoparticles, has a larger impact on rectification than altering the water conductivity, which is higher. If interfacial temperature discontinuities can be engineered across macroscale interfaces as is natural for nanoscale systems, these also lead to significant increase in rectification.