Flow Evaporation of Confined Thin Liquid Films on the Hybrid Surfaces

Advanced high-power electronic devices require phase-change cooling technologies with high-heat-flux dissipation and low thermal resistance. Conventional capillary evaporation in porous wicks enables rapid heat removal through thin liquid films, whereas enclosed microchannel flow boiling enhances the liquid supply with high-pressure pumping. Here, we report flow evaporation of a confined thin liquid film on hybrid surfaces for both rapid heat transfer and timely vapor expulsion. The structure with asymmetric wettability provides an additional interfacial pressure that increases the maximum stable liquid supply rate while maintaining an ultrathin liquid film, enabling efficient evaporation and heat dissipation with a low thermal resistance. The generated vapor is discharged in situ through the hydrophobic foam layer, avoiding two-phase flow instability caused by the vapor accumulation. Micro-PIV and high-speed imaging show that the confined liquid film increases the maximum stable liquid supply rate and local liquid velocity by 34-fold and 3-fold, respectively, when compared with a free capillary liquid film. For flow evaporation, the average and maximum surface temperatures are reduced by 8.4% and 6.4%, respectively, and the temperature uniformity is improved by 35.7%. The insights obtained from flow evaporation can guide the design and fabrication of efficient thermal-management devices.