Nanograssed Micropyramidal Architectures for Continuous Dropwise Condensation

TLDR

Dropwise condensation is essential for thermal management and water harvesting, yet designing surfaces that enable both efficient droplet nucleation and self‑removal is difficult because nucleation requires wettability while departure demands super‑hydrophobicity. This study demonstrates that a hierarchical nanograssed micropyramid architecture can reconcile these opposing requirements. The architecture provides global super‑hydrophobicity with locally wettable nucleation sites, boosting drop number density by ~65 % and self‑removal volume by ~450 % versus nanostructure‑only surfaces. The synergistic interaction of the multiscale structures sustains continuous nucleation, coalescence, departure, and re‑nucleation, enabling prolonged dropwise condensation and offering new opportunities for high‑performance cooling and water‑condenser surfaces.

Abstract

Abstract Engineering the dropwise condensation of water on surfaces is critical in a wide range of applications from thermal management (e.g. heat pipes, chip cooling etc.) to water harvesting technologies. Surfaces that enable both efficient droplet nucleation and droplet self‐removal (i.e. droplet departure) are essential to accomplish successful dropwise condensation. However it is extremely challenging to design such surfaces. This is because droplet nucleation requires a wettable surface while droplet departure necessitates a super‐hydrophobic surface. Here we report that these conflicting requirements can be satisfied using a hierarchical (multiscale) nanograssed micropyramid architecture that yield a gobal superhydrophobicity as well as locally wettable nucleation sites, allowing for ˜65% increase in the drop number density and ˜450% increase in the drop self‐removal volume as compared to a superhydrophobic surface with nanostructures alone. Further we find that synergistic co‐operation between the hierarchical structures contributes directly to a continuous process of nucleation, coalescence, departure, and re‐nucleation enabling sustained dropwise condensation over prolonged periods. Exploiting such multiscale coupling effects can open up novel and exciting vistas in surface engineering leading to optimal condensation surfaces for high performance electronics cooling and water condenser systems.