Nanoscale-Agglomerate-Mediated Heterogeneous Nucleation.
Hyeongyun ChaAlex WuMoon-Kyung KimKosuke SaigusaAihua LiuNenad MiljkovicPublished in: Nano letters (2017)
Water vapor condensation on hydrophobic surfaces has received much attention due to its ability to rapidly shed water droplets and enhance heat transfer, anti-icing, water harvesting, energy harvesting, and self-cleaning performance. However, the mechanism of heterogeneous nucleation on hydrophobic surfaces remains poorly understood and is attributed to defects in the hydrophobic coating exposing the high surface energy substrate. Here, we observe the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), microgoniometric contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of sulfuric acid based aerosol particles inside the droplet and adsorption of volatile organic compounds such as methanethiol (CH3SH), dimethyl disulfide (CH3SSCH), and dimethyl trisulfide (CH3SSSCH3) on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation after evaporation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces.
Keyphrases
- ionic liquid
- electron microscopy
- high resolution
- aqueous solution
- room temperature
- atomic force microscopy
- biofilm formation
- air pollution
- single molecule
- pseudomonas aeruginosa
- particulate matter
- computed tomography
- energy transfer
- heat stress
- working memory
- solid state
- magnetic resonance imaging
- cystic fibrosis
- dual energy