.png){kind=icon}
.png){kind=icon}
Return
Hydrophilicity and Hydrophobicity at the Nanoscale: A Theoretical Study on Two-Dimensional Cylindrical Droplets with Disjoining Pressure Effects
.png){kind=icon}
PRE
AI
I
DOI：10.3390/liquids6010011.png)
.png){kind=icon}
Original request for help.png){kind=icon}
Share.png){kind=icon}
Save
Abstract
En 中文
Hydrophobicity and hydrophilicity are incompatible in the sense that a single substrate cannot exhibit both characteristics simultaneously. On a hydrophobic substrate, for example, a macroscopic droplet always exhibits a morphology with a contact angle higher than 90 degrees, never lower than 90 degrees. In this paper, we theoretically demonstrate the possibility that a nanoscale droplet can exhibit a contact angle lower than 90 degrees on the same hydrophobic substrate. To demonstrate this, we analyze the morphology and contact angle of a sessile droplet on smooth flat substrates, taking into account disjoining pressure of Lennard-Jones type. By constraining the two-dimensional cylindrical droplet and minimizing the free-energy functional, we derive a formula to determine the droplet's morphology and the boundary between hydrophilic and hydrophobic contact angles for finite-sized droplets. Using this formulation, we reconsider the formula for the macroscopic contact angle, known as the Derjaguin-Frumkin formula. By utilizing a simple disjoining pressure model, we find that the calculated contact angle at the nanoscale is always smaller than the macroscopic contact angle determined by the Derjaguin-Frumkin formula. Consequently, the wettability (hydrophilicity/hydrophobicity) differs at the nanoscale compared to the macroscale. We further discuss the implication of our results on the size-dependent contact angle and line tension at the nanoscale.
Keywords:
hydrophilicity
hydrophobicity
disjoining pressure
contact angle
nanoscale
Journal
L
IF:
0
Papers:
22
Citations:
0
Organization
Cited Papers