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Disjoining Pressure in Partial Wetting on the Nanoscale
Florentina Samoila1, Lucel Sirghi1
1Iasi Plasma Advanced Research Center (IPARC), Faculty of Physics, "Alexandru Ioan Cuza", University of Iasi , Iasi-700506, Romania.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 10, 2017
Summary
Nanoscale liquid droplets deviate from spherical shapes due to molecular forces. Surface modification of glass with oleic acid created strong negative disjoining pressure, altering nanodroplet shape significantly.
Area of Science:
- Nanoscale science
- Surface science
- Physical chemistry
Background:
- Partial wetting on the nanoscale leads to sessile liquid nanodroplets on substrates.
- Molecular forces at nanodroplet interfaces are significant and can be described by disjoining pressure.
- This pressure causes deviations from the ideal spherical cap shape observed in nanodroplets.
Purpose of the Study:
- To investigate the influence of molecular forces and surface modification on the shape of sessile nanodroplets.
- To analyze the deviation from spherical cap shape in oleic acid nanodroplets on glass.
- To understand the role of disjoining pressure in nanodroplet morphology.
Main Methods:
- Utilized atomic force microscopy (AFM) to image sessile nanodroplets of oleic acid on glass.
- Manipulated disjoining pressure through hydroxylation of the glass surface.
- Integrated the augmented Young-Laplace equation with an exponential decay model for disjoining pressure.
Main Results:
- Observed significant deviations from spherical cap shape in oleic acid nanodroplets.
- Surface hydroxylation induced strong negative disjoining pressure due to molecular orientation.
- Experimental height profiles of nanodroplets closely matched theoretical predictions.
Conclusions:
- Molecular forces, specifically negative structural disjoining pressure, profoundly impact nanodroplet shape.
- Surface modification is a viable method to control nanodroplet morphology.
- The augmented Young-Laplace equation accurately models nanodroplet behavior under these conditions.
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