Probing Micro-Newton Forces on Solid/Liquid/Gas Interfaces Using Transmission Phase Shift.

Area of Science:

• Physics and Chemistry of Interfaces
• Fluid Dynamics
• Nanotechnology

Background:

• Capillary interactions at solid/liquid/gas interfaces are fundamental to many natural and life systems.
• Understanding forces at these interfaces is crucial for various scientific and engineering applications.

Purpose of the Study:

• To present a novel profilometry technique for high-resolution 3D visualization of liquid/gas interfaces.
• To investigate the influence of particle radius on forces at solid/liquid/gas interfaces.
• To generalize Archimedes' principle by incorporating surface tension effects for small-scale phenomena.

Main Methods:

• Development and application of transmission phase shift profilometry for interface visualization.
• Measurement of micro-Newton forces at solid/liquid/gas interfaces.
• Analysis of particle behavior (floating vs. sinking) based on the Bond number.

Main Results:

• The study provides the first direct evidence that surface tension plays a critical role in the floating/sinking behavior of small particles.
• Dominant regimes for floating particles were identified and correlated with the Bond number.
• Measured forces were in the micro-Newton range, demonstrating the sensitivity of the technique.

Conclusions:

• Archimedes' principle needs generalization to include surface tension for accurate predictions at small scales.
• The transmission phase shift technique is a powerful tool for studying capillarity and interface phenomena.
• This methodology may inform the design of future liquid microbalances and advanced interfacial measurement devices.