Recurrent Filmwise and Dropwise Condensation on a Beetle Mimetic Surface

TLDR

Vapor condensation is critical for power generation, thermal management, water harvesting, and desalination, yet achieving fast droplet nucleation, efficient departure, and low thermal resistance requires balancing surface roughness and chemistry—a challenge that has largely been addressed only for dropwise condensation on superhydrophobic surfaces. This study develops a beetle‑mimetic hybrid surface with high wetting contrast to seamlessly integrate filmwise and dropwise condensation modes. An analytical model is proposed to optimize the surface morphology for dramatic heat‑transfer enhancement. The hybrid surface yields recurrent condensation modes that improve droplet nucleation density, growth rate, self‑removal, and overall heat‑transfer coefficient.

Abstract

Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation and efficient droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, these properties have conflicting requirements on the structural roughness and surface chemistry of the condensing surface or condensation modes (e.g., filmwise vs dropwise). Despite intensive efforts over the past few decades, almost all studies have focused on the dropwise condensation enabled by superhydrophobic surfaces. In this work, we report the development of a bioinspired hybrid surface with high wetting contrast that allows for seamless integration of filmwise and dropwise condensation modes. We show that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient. Moreover, we propose an analytical model to optimize the surface morphological features for dramatic heat transfer enhancement.