Trapping of Gas Bubbles in Water at a Finite Distance below a Water-Solid Interface

Area of Science:

• Physics of interfaces
• Colloid and surface science
• Microfluidics

Background:

• Buoyancy drives gas bubbles upward in water-filled cavities.
• Near surfaces, Lifshitz, double layer, and hydrodynamic forces influence bubble behavior.
• Controlling microbubble behavior is crucial for various applications.

Purpose of the Study:

• To demonstrate stable trapping of micrometer-sized bubbles near uncharged metallic and dielectric surfaces.
• To investigate the influence of surface material and charge on bubble trapping distances.
• To explore the role of Lifshitz and buoyancy forces in microbubble stabilization.

Main Methods:

• Theoretical modeling of forces acting on gas bubbles near surfaces.
• Experimental investigation using various metallic (Al, Au, Ag) and dielectric (silica, polystyrene) surfaces.
• Tunable trapping distances achieved by altering surface materials.

Main Results:

• Micrometer-sized bubbles (1-10 μm radius) were stably trapped at distances of 35-190 nm.
• Repulsive Lifshitz forces combined with buoyancy enable stable trapping below uncharged surfaces.
• Surface charges were shown to enhance bubble trapping through ion adsorption forces.
• Large bubbles (≥100 μm) were typically repelled from the surface by buoyancy.

Conclusions:

• Stable trapping of micrometer-sized bubbles is achievable and tunable via surface properties.
• Lifshitz forces play a critical role in stabilizing microbubbles near surfaces.
• Surface charge significantly enhances bubble trapping, broadening potential applications.