Achieving robust and enhanced pool boiling heat transfer using micro-nano multiscale structures

Vapor chamber thermal management technology has become a high-reliability cooling method to solve the heat dissipation problem. However, this is still a crucial challenge to overcome when the capillary wick is exposed to harsh service environments. In this paper, a fabrication method of capillary wicks with micro-nano multiscale structures combining micro hot embossing and high-pressure hydrothermal treatment is proposed. Micro pyramid-channel is fabricated by micro hot embossing, and when the axis-to-diameter ratio of nanobars reaches 3.16-3.17, superhydrophilicity is realized. In the pool boiling experiment, the heat transfer performance of the pyramid-channel is better than that of the triangular-channel. Importantly, the superhydrophilic micro-nano structures achieve significantly improved critical heat flux and heat transfer coefficient simultaneously, increased by 162.1% and 180.8%. Moreover, the fabricated micro-nano capillary wick, which comprise high-strength pyramid-channel and specific wettability nanostructures, can maintain their outstanding superhydrophilicity and superhydrophobicity and their enhanced boiling property even after high-pressure high-velocity fluid scouring. The proposed cost-effective fabrication method provides an ideal and industrialized approach for the mass production of vapor chamber capillary wicks suitable for severe application environments.