Hierarchical biphilic micro/nanostructures for a new generation phase-change heat sink

Pushing the critical heat flux (CHF) limit in boiling has been a century-old challenge. Overcoming this challenge can greatly benefit advancements of myriad devices in which a large quantity of heat must be removed from a small surface. The occurrence of CHF is accompanied by the formation of significant vapor adjacent to the heated surface, such that liquid cannot rewet the surface. Here, a new concept is implemented to ensure that liquid always displaces the vapor near the heated surface. In the new approach, flow is constrained within a hydrophilic microstructure by a hydrophobic vapor-permeable nanostructure. A bubble bounded between the two structures is pulled away from the hydrophilic heated structure and discharged from the flow, thus leading to a fundamental change in CHF dynamics. The performance of a device based on this principle exceeded that of prior studies, with some metrics exhibiting an order of magnitude improvement.