Abstract
This study conducted molecular dynamics simulations to estimate the behavior of water and oil droplets on the same surface and to investigate how oil droplets respond to varying surface conditions. The surfaces were considered from a flat plate to pillared surfaces with varying heights. Additionally, three surface conditions were examined by altering the solid-surface characteristic energy: lipophobic (weakly hydrophobic), weak lipophobic, and lipophilic conditions. The results showed that as the pillar height increased, the contact angle of the water droplet on the weak hydrophobic surfaces increased, while that of the 1, 2-dichloroethane (DCE) droplet remained relatively constant. In the case of weak lipophobic conditions, the top and bottom parts of the DCE droplet exhibited distinct behaviors as the pillar height increased. Furthermore, under lipophilic conditions, the oil droplets displayed varying patterns in their shape changes with increasing pillar height. These findings imply that droplet behavior on surfaces can be manipulated by engineering structures without necessitating additional external forces or energy inputs. This research provides valuable insights into the potential for separating and merging different types of liquids.
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Abbreviations
- A n :
-
Dihedral coefficient
- H :
-
Pillar height
- K angle :
-
Angle constant
- K bond :
-
Bond constant
- q :
-
Electric charge
- r ij :
-
Distance between a pair of atoms i and j
- U total :
-
Total potential between atom and molecules
- U bond :
-
Potential by bonding
- U angle :
-
Potential by bending
- U dihedral :
-
Potential by torsion
- U coulomb :
-
Coulomb potential
- U LJ :
-
Lennard-Jones potential
- ε ij :
-
Characteristic energy between a pair of atoms i and j
- σ ij :
-
Characteristic length between a pair of atoms i and j
- θ :
-
Angle between three atoms
- γ LG :
-
Surface tension of the liquid
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Acknowledgments
This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2019R1A5A8083201). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (RS-2023-00239843).
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Yun Ji Kang received her M.S. degree from Pusan National University, South Korea in 2023. Her research interests are focused on molecular dynamics and computational fluid dynamics.
Man Yeong Ha received his B.S. degree from Pusan National University, Korea, in 1981, M.S. degree, in 1983, from Korea Advanced Institute of Science and Technology, Korea, and Ph.D. degree from Pennsylvania State University, USA in 1990. Dr. Ha is currently a Professor at the School of Mechanical Engineering at Pusan National University in Busan, Korea. He served as an Editor of the Journal of Mechanical Science and Technology. He is the member of Honorary Editorial Advisory Board of the International Journal of Heat and Mass Transfer. His research interests are focused on thermal management, computational fluid dynamics, and micro/nano fluidics.
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Kang, Y.J., Kwon, T.W. & Ha, M.Y. Investigation of the behavior of water and oil droplets on nanostructured surfaces: a molecular dynamics simulation study. J Mech Sci Technol 38, 1249–1257 (2024). https://doi.org/10.1007/s12206-024-0220-z
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DOI: https://doi.org/10.1007/s12206-024-0220-z