Enhanced pool boiling heat transfer performance of top-patterned nanowire micropillar array surface fabricated by selective etching

With the rapid increase in electronic-device power density, efficient and stable phase-change heat dissipation has become a key challenge in advanced thermal management. Micro- and nanostructured hybrid surfaces can enhance boiling heat transfer, but surfaces fully covered with nanostructures often lead to spatial overlap between nucleation, vapor removal, and liquid replenishment. This spatial overlap leads to vapor accumulation and local dryout at high heat fluxes. To address this issue, this study proposes a spatially selective nanostructure functional regulation strategy to control vapor-liquid transport on microstructured surfaces. A top-patterned nanowire micropillar array surface was fabricated through mask design and photolithography-assisted selective etching, combining deep reactive ion etching (DRIE) with metal-assisted chemical etching (MACE). In this structure, silicon nanowires are selectively introduced onto micropillar tops as active nucleation regions with capillary-assisted replenishment, while non-nanowire-covered regions provide low-resistance liquid transport pathways. Compared with smooth silicon, nanowire, micropillar array, and nanowire-covered micropillar hybrid surfaces, the proposed surface exhibited the best overall boiling performance, achieving a critical heat flux (CHF) of 278.5 W/cm 2 and a maximum heat transfer coefficient (HTC) of 9.41 W/(cm 2 ·K). These values correspond to increases of 195.59% and 379.55%, respectively, relative to smooth silicon, and further increases of 14.28% and 5.48%, respectively, compared with the nanowire-covered micropillar hybrid surface. The enhanced performance is attributed to a spatially separated vapor-liquid transport pathway featuring top nucleation and bottom liquid replenishment, which mitigates bubble coalescence, delays vapor film formation, and enables simultaneous enhancement of CHF and HTC.