Hierarchical micro-nano surfaces with multi-functional synergy for boiling two-phase thermal management

Boiling phase-change emerges as a superior thermal management solution for high-power electronics, overcoming the limitations of air cooling in immersion cooling systems for data centers. While liquid-vapor phase change offers exceptional heat dissipation potential, three key challenges remain. These include nucleate boiling initiation hysteresis, a limited heat transfer coefficient, and low critical heat flux. This study proposes a hierarchical architecture combining a 3-dimensional copper cage for enhanced thermal transport through extended interfaces and preserved vapor pathways, with laser-etched microcavities activating bubble nucleation, along with vertically aligned copper foam rods with superhydrophilic CuO nanocoatings for capillary-driven liquid supply. The synergistic design achieves nearly 8 °C reduction for onset of nucleation boiling, 95 % heat transfer coefficient improvement, and 367.7 W/cm 2 in critical heat flux (273 % over plain copper). This tri-level architecture fundamentally resolves the inherent heat transfer coefficient-critical heat flux trade-off by synchronously optimizing nucleation dynamics through microcavity array, phase-change kinetics via the 3-dimensional cage's transport channels, and liquid sustainability through superhydrophilic foam rods' capillary wicking - achieving concurrent enhancement of boiling initiation, heat transfer intensity, and dry-out prevention. The scalable fabrication combining laser processing and electrochemical growth ensures industrial viability. These advancements establish new thermal management benchmarks for high power devices requiring >300 W/cm 2 heat flux dissipation.