High-efficiency thermal diodes enabled by unidirectional capillary fluid transport and phase change

This is the authors' abstract. We don't add key points for this paper.

Thermal diodes enable controlled one-way heat transfer, making them critical for energy harvesting and thermal management. Existing thermal diodes face limitations, including short heat transport distances, geometric constraints, and low diodicity. Herein, we propose a thermal diode enabled by unidirectional liquid transport structures (ULTSs), which utilize unidirectional capillary transport and the latent heat of working fluids to achieve high thermal diodicity over long distances. The 3D-printed microporous hierarchical structures, which incorporate V-grooves and asymmetric wedge-shaped microcavities, are optimized via machine learning to enable fast, unidirectional, long-range, and passive fluid transport driven by capillary forces. By integrating the ULTS with a flat plate heat pipe, the flow circulation between the evaporator and condenser is effectively regulated. A remarkable thermal diodicity of 16.2 is achieved for a separation distance of 85 mm between the cold and heat sources. The gravity-independent operation highlights its potential for applications in portable devices and aerospace technologies.