Abstract
This study investigated water vapor condensation on superhydrophobic surfaces (SHSs) featuring micropillars enclosed by wall lattices and having three-tier hierarchical roughness. A total of five samples were created with three (NW-J, W200-J and W400-J samples) having large micropillar depth (∼6 μm) and two (NW-S and W200-S samples) having small micropillar depth (∼1 μm). Two distinct condensate removal modes were observed during condensation: coalescence-induced jumping on samples with large micropillar depth and coalescence-induced shedding on samples with small micropillar depth. The results showed that the diameter of the shedding droplet on the W200-S sample having small micropillar depth could be as small as 107 μm, as compared to the theoretical critical diameter of 267 μm for gravitational shedding on the same sample. The enhanced functionality of the three-tier nanotextures on the W200-S sample could effectively suppress localized pinning of the three-phase contact line and Wenzel neck formation during the growth of condensate droplets. Consequently, during multidroplet coalescence, the released surface energy easily overcomes the solid-liquid adhesion, leading to spontaneous shedding of merged droplets. The inclusion of the wall lattice aids condensate growth by the droplet self-alignment along the walls and promoting coalescence. As a result, the W200-S sample exhibited the highest condensate collection as well. The proposed surface design has great potential for scaling up and implementation in heating, ventilation, and air-conditioning equipment due to the simplicity of the surface morphology and the facile spray-coating method used to achieve hierarchical roughness.
| Original language | English |
|---|---|
| Pages (from-to) | 12782-12796 |
| Number of pages | 15 |
| Journal | ACS Applied Materials and Interfaces |
| Volume | 17 |
| Issue number | 8 |
| DOIs | |
| State | Published - Feb 26 2025 |
Funding
This work was supported by the Mitsubishi Heavy Industries Thermal Systems, Japan, and partly supported by \u201CAdvanced Research Infrastructure for Materials and Nanotechnology in Japan (ARIM)\u201D of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, Grant Numbers JPMXP1222UT1035 and JPMXP1223UT1140. N.M. gratefully acknowledges funding support from the International Institute for Carbon Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology. J.A.S. and K.N. gratefully acknowledge the U.S. Department of Energy Building Technologies Office (BTO) for funding support. J.A.S. and K.N. gratefully acknowledge Stephen P Kowalski and Pengtao Wang from the Multifunctional Equipment Integration Group, Building and Transportation Science Division, Oak Ridge National Laboratory, for internally reviewing the manuscript. This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://www.energy.gov/doe-public-access-plan).
Keywords
- coalescence
- contact line pinning
- dropwise condensation
- hierarchical roughness
- jumping
- shedding
- superhydrophobic surface