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Resolving the Pinning Force of Nanobubbles with Optical Microscopy
Beng Hau Tan1, Hongjie An1, Claus-Dieter Ohl1
1Cavitation Lab, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Physical Review Letters
|February 18, 2017
Summary
Researchers experimentally quantified the pinning force of surface nanobubbles, finding it to be around 0.1μN. This force is crucial for understanding nanobubble properties and stability on substrates.
Area of Science:
- Surface science
- Nanotechnology
- Physical chemistry
Background:
- Surface nanobubbles exhibit unique properties like small contact angles and long lifetimes.
- These properties are attributed to a pinning force that anchors nanobubbles to substrates.
- This critical pinning force has not been experimentally quantified previously.
Purpose of the Study:
- To experimentally determine the magnitude of the pinning force of surface nanobubbles.
- To investigate the mechanical response of nanobubbles under external pulling forces.
- To understand the factors influencing nanobubble detachment from substrates.
Main Methods:
- Utilized atomic force microscopy (AFM) to apply controlled pulling forces to surface-attached nanobubbles.
- Employed total internal reflection fluorescence microscopy (TIRFM) to observe the nanobubbles' mechanical responses during pulling.
- Correlated AFM force measurements with TIRFM observations to estimate the pinning force.
Main Results:
- Estimated the pinning force required to unpin a surface nanobubble to be on the order of 0.1μN.
- Identified the stability of the pulled neck as a limiting factor for the maximum tip force.
- Observed that tip hydrophobicity enhances the force the tip can exert on the nanobubble.
Conclusions:
- The study provides the first experimental quantification of surface nanobubble pinning force.
- The results offer crucial insights into the adhesion mechanisms and stability of nanobubbles.
- Understanding pinning forces is essential for controlling and utilizing nanobubble behavior in various applications.
