Abstract
Evaporation of small water droplets on solids is hindered because surface tension pulls the droplet into a spherical cap that has a small perimeter. Our solution is to coat a solid with a very thin, porous layer into which the droplet flows to create a large-area disk with concomitant high rate of evaporation. We investigate evaporation by varying factors that have not been previously considered: pore size and distribution, contact angle, temperature, and relative humidity (RH). A larger pore size resulted in faster evaporation, which we explain through faster transport within the coating. Even faster evaporation occurred for a bilayer structure with small particles on the air side and larger particles on the solid side. The water advancing contact angle had an insignificant effect in the range from < 10° through to 60°. Our results for different pore sizes, temperature, humidity, and contact angle all collapse onto a single curve when appropriately normalized. This validates an equation that can be used for the evaporation from a homogeneous coating that depends only one empirical factor and the droplet volume. Since the volume is often user-controlled, we envisage that this equation can be used to predict evaporation and guide design of fast-drying coatings.
| Original language | English |
|---|---|
| Pages (from-to) | 369-379 |
| Number of pages | 11 |
| Journal | Journal of Colloid and Interface Science |
| Volume | 678 |
| DOIs | |
| State | Published - Jan 15 2025 |
Funding
The authors thank Yuxuan Zhang at Oak Ridge National Laboratory for helping with neutron imaging. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to MARS on proposal number IPTS-31740.1. This work was performed in part at the Nanoscale Characterization and Fabrication Laboratory, which is supported by the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (Nano Earth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by NSF (ECCS 1542100 and ECCS 2025151). Mohsen Hosseini acknowledges the funding through the David W. and Lillian Francis Memorial Fellowship at Virginia Tech. The authors thank the Surface Analysis Laboratory in the Department of Chemistry at Virginia Tech, which is supported by the National Science Foundation under Grant No. CHE-1531834, for capturing the XPS spectrum, and Thomas Staley for providing facilities for initial tests for the fabrication of coatings. The authors also acknowledge DataPhysics for lending us contact angle goniometer used in this study. The authors thank Yuxuan Zhang at Oak Ridge National Laboratory for helping with neutron imaging. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory . This work was performed in part at the Nanoscale Characterization and Fabrication Laboratory, which is supported by the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (Nano Earth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by NSF ( ECCS 1542100 and ECCS 2025151 ). Mohsen Hosseini acknowledges the funding through the David W. and Lillian Francis Memorial Fellowship at Virginia Tech . The authors thank the Surface Analysis Laboratory in the Department of Chemistry at Virginia Tech, which is supported by the National Science Foundation under Grant No. CHE-1531834, for capturing the XPS spectrum, and Thomas Staley for providing facilities for initial tests for the fabrication of coatings. The authors also acknowledge DataPhysics for lending us contact angle goniometer used in this study.
| Funders | Funder number |
|---|---|
| Office of Science | |
| David W. and Lillian Francis Memorial Fellowship at Virginia Tech | |
| Oak Ridge National Laboratory | IPTS-31740.1 |
| Oak Ridge National Laboratory | |
| National Science Foundation | CHE-1531834, ECCS 1542100, ECCS 2025151 |
| National Science Foundation |
Keywords
- Coating
- Droplet
- Evaporation
- Imbibition
- Porous