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Counter-intuitive penetration of droplets into hydrophobic gaps in theory and experiment

Hagg, Daniel ; Eifert, Alexander ; Dörr, Aaron ; Bodziony, Francisco ; Marschall, Holger (2023)
Counter-intuitive penetration of droplets into hydrophobic gaps in theory and experiment.
In: Scientific Reports, 13 (1)
doi: 10.1038/s41598-023-43138-2
Article, Bibliographie

Abstract

Droplets that spontaneously penetrate a gap between two hydrophobic surfaces without any external stimulus seems counterintuitive. However, in this work we show that it can be energetically favorable for a droplet to penetrate a gap formed by two hydrophobic or in some cases even superhydrophobic surfaces. For this purpose, we derived an analytical equation to calculate the change in Helmholtz free energy of a droplet penetrating a hydrophobic gap. The derived equation solely depends on the gap width, the droplet volume and the contact angle on the gap walls, and predicts whether a droplet penetrates a hydrophobic gap or not. Additionally, numerical simulations were conducted to provide insights into the gradual change in Helmholtz free energy during the process of penetration and to validate the analytical approach. A series of experiments with a hydrophobic gap having an advancing contact angle of 115°, a droplet volume of about 10 μL and different gap widths confirmed the theoretical predictions. Limits and possible deviations between the analytical solution, the simulation and the experiments are presented and discussed.

Item Type: Article
Erschienen: 2023
Creators: Hagg, Daniel ; Eifert, Alexander ; Dörr, Aaron ; Bodziony, Francisco ; Marschall, Holger
Type of entry: Bibliographie
Title: Counter-intuitive penetration of droplets into hydrophobic gaps in theory and experiment
Language: English
Date: 2023
Place of Publication: London
Publisher: Macmillan Publishers Limited, Springer Nature
Journal or Publication Title: Scientific Reports
Volume of the journal: 13
Issue Number: 1
Collation: 12 Seiten
DOI: 10.1038/s41598-023-43138-2
URL / URN: https://www.nature.com/articles/s41598-023-43138-2
Abstract:

Droplets that spontaneously penetrate a gap between two hydrophobic surfaces without any external stimulus seems counterintuitive. However, in this work we show that it can be energetically favorable for a droplet to penetrate a gap formed by two hydrophobic or in some cases even superhydrophobic surfaces. For this purpose, we derived an analytical equation to calculate the change in Helmholtz free energy of a droplet penetrating a hydrophobic gap. The derived equation solely depends on the gap width, the droplet volume and the contact angle on the gap walls, and predicts whether a droplet penetrates a hydrophobic gap or not. Additionally, numerical simulations were conducted to provide insights into the gradual change in Helmholtz free energy during the process of penetration and to validate the analytical approach. A series of experiments with a hydrophobic gap having an advancing contact angle of 115°, a droplet volume of about 10 μL and different gap widths confirmed the theoretical predictions. Limits and possible deviations between the analytical solution, the simulation and the experiments are presented and discussed.

Uncontrolled Keywords: SFB1194_B07
Additional Information:

Artikel-ID: 16518

Divisions: DFG-Collaborative Research Centres (incl. Transregio)
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 1194: Interaction between Transport and Wetting Processes
Date Deposited: 07 Dec 2023 12:29
Last Modified: 07 Dec 2023 12:29
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