Tunable Phase Change on Nanoengineered Surfaces
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. We developed a hierarchical (multiscale) nanograssed micropyramid architecture that yield a global superhydrophobicity as well as locally wettable nucleation sites and, therefore, enable both efficient droplet nucleation and droplet self‐removal to accomplish successful dropwise condensation. This work is featured as a Front Cover in (Advanced Functional Materials ,2011)
We further elucidate the mechanism of recurrent filmwise and dropwise condensation modes on a beetle mimetic surface of hybrid structures with high wetting contrast (biphilic interface), which 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 (ACS Nano, 2015, Front Cover). We conducted modeling and simulation for the optimization of condensation heat transfer at biphilic interface (IJHMT, 2018). We developed electrospraying method for scalable manufacturing of the biphilic surfaces on metal substrates and efficient water harvesting performance achieved by the fabricated surfaces (ACS Nano, 2018).
Preventing or minimizing ice formation in supercooled water at the interface is of prominent importance in many infrastructures, transportation, and cooling systems. The overall phase change heat transfer on icephobic surfaces, in general, is intentionally sacrificed to suppress the nucleation of water and ice. However, inhibiting freezing without compromising the water condensation has been an unsolved challenge. We discovered that our biphilic structures can tune the nucleation rates of water and ice in the sequential condensation-to-freezing process, enabling the suppression of ice formation while sustaining rapid water condensation (Physical Review Letters, 2018).