Nanobubbles and the nanobubble bridging capillary force.

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Nanotechnology

Background:

• Hydrophobic interactions at nanometer scales are crucial in biology and industry.
• Classical theories fail to explain the observed long-range hydrophobic attraction between surfaces in aqueous solutions.
• This attraction is often attributed to an artifact: the formation of submicroscopic bubbles (nanobubbles).

Purpose of the Study:

• To review experimental findings on nanobubbles and their associated capillary forces.
• To clarify the phenomena of nanobubble formation and stability.
• To bridge the gap between experimental evidence and theoretical understanding of hydrophobic forces.

Main Methods:

• Review of experimental force spectroscopy studies, including atomic force microscopy and surface-force apparatus.
• Analysis of existing theories on nanobubble stability and formation.
• Synthesis of experimental results to explain hydrophobic attraction.

Main Results:

• The long-range hydrophobic attraction is often caused by the coalescence of nanobubbles, forming a gaseous capillary bridge and a capillary force.
• Experimental evidence for nanobubbles is substantial, though theoretical understanding remains incomplete.
• Nanobubbles play a significant role in interfacial phenomena between hydrophobic surfaces in water.

Conclusions:

• Nanobubbles provide a plausible explanation for the anomalous hydrophobic force.
• Further theoretical development is needed to fully understand nanobubble behavior and their impact on interfacial forces.
• This review consolidates current knowledge, highlighting the importance of nanobubbles in aqueous systems.