Related Experiment Video
Updated: Jun 8, 2025
Microtensiometer for Confocal Microscopy Visualization of Dynamic Interfaces
Published on: September 9, 2022
Distinct Contributions of Particle Adsorption and Interfacial Compression to the Surface Pressure of a Fluid
Yu Fu1, Joelle Frechette1,2
1Chemical and Biomolecular Engineering Department, University of California, Berkeley, Berkeley, California 94760, United States.
Abstract:
Particle-laden interfaces stabilize emulsions and foams and can serve as a platform for multiscale materials. Favorable wetting of a particle to a fluid interface reduces the apparent interfacial tension through area replacement with a linear relationship between the apparent surface pressure and the particle area fraction. The area replacement model is widely employed, often up to particle area fraction reaching the maximum hexagonal packing. However, data directly supporting the area replacement model are limited, and the description ignores contributions from particle-particle interactions and does not describe the surface pressure during the compression of a particle-laden interface. This work reports on the direct validation of the area replacement model through the direct measurement of the adsorption energy, surface pressure, and area fraction of adsorbed particles. Experiments combining tensiometry and confocal imaging during the adsorption of colloidal particles to the oil-water interface confirm the area replacement model within the observed range of area fraction, but only when the drop area is kept constant. Results highlight the importance of keeping the droplet area constant during particle adsorption to extract the adsorbed amount from tensiometry experiments. As particles adsorb to the interface, the droplet area tends to change and compresses or expands the interface. This change in area is associated with an increase in area fraction at nearly constant surface pressure, which deviates from the area replacement model. In contrast to particle adsorption, slow compression of the fluid interface leads to a negligible change in surface pressure up to an area fraction of η ∼ 0.26 for the materials systems investigated. Increase in surface pressure during compression is due to particle-particle interactions, while compression at higher strain rates introduces additional contributions from interfacial rheology.
More Related Videos
08:58Atomic Force Microscopy Cantilever-Based Nanoindentation: Mechanical Property Measurements at the Nanoscale in Air and Fluid
Published on: December 2, 2022
13:15Quantitative and Qualitative Examination of Particle-particle Interactions Using Colloidal Probe Nanoscopy
Published on: July 18, 2014
Related Concept Videos
02:57Surface Tension, Capillary Action, and Viscosity
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
01:14Fluid Pressure
According to Pascal's law, a fluid at rest will generate equal pressure in all directions. This pressure is measured as a force per unit area, and its magnitude depends on the fluid's specific...
01:14Pressure of Fluids
01:16Surface Tension and Surface Energy
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
01:22Surface Tension of Fluid
Surface tension varies...
01:15Concept of Pressure at a Point
In a fluid at rest, pressure acts equally in...