Vapor Chamber Thermal Diode with Laser- fabricated Wickless Components

In this study, a vapor chamber - thermal diode apparatus is fabricated and tested. The system's components are laser-functionalized, wickless, and wettability-patterned copper plates. This is the first thermal management component that is completely wick-free and operates due to surface modification and wettability patterning instead of utilizing wicks or any kind of wicking structures. Our approach takes advantage of the phase-changing property of water in a closed loop composed of two initially identical copper plates, one acting as an evaporator, and the other designed as a condenser. The plates have different wettability patterns, each especially designed/engineered to transform the simple flat rectangular copper plate to a functional component of a vapor chamber. The apparatus, while operating as a vapor chamber, displays a thermal resistance as low as 0.07 ± 0.01 K/W, and while operating as a thermal diode, it shows a diodicity, defined as the heat flux ratio in forward and reverse operation, as high as 9. This value demonstrates the system's ability to effectively remove the heat from a heat source (i.e., electronic chip) while, in parallel, protecting it from damage by excessive heat backflow. The diodicity of the diode is ascribed to the different wettability-pattern designs on the two copper plates comprising the system. On the forward mode, the two patterns work as designed to enable heat transfer, but on the reverse mode, the patterns no longer function harmoniously with each other, and the heat transfer is hindered. The simplicity of the design and its moderate dimensions are important advantages that make this new thermal management component attractive for engineering applications.