Enhanced evaporation performance on a novel microstructured surface with vertical dimension gradient

The wick design is critical for vapor chamber or flat heat pipes based on phase-change heat dissipation. Typically, the high-performance wick is governed by geometry, topology, and the microfabrication constraints. In this article, a novel microstructure incorporating gradient dimension optimization design is proposed to co-enhance the processes of thin film evaporation and capillary pumping. The numerical work systematically studies the parametric effect of wick porosity, contact angle, microstructure layout and Marangoni convection on the performance for different wicks. This novel structure with pyramid-like topology can promote the wick performance because it not only improves the capillary performance, but also shows high effective heat flux not that apparently influenced by contact angle. Meanwhile, the gradient cuboid microstructure and gradient microchannel are fabricated by a cost-effectively one-step hot micro-embossing process and compared with traditional microstructures by macro-scale evaporation test. The temperature distribution and excellent evaporation rate on gradient cuboid surface show satisfactory effect agrees with numerical results.