Lateral hydrodynamic interactions between an emulsion droplet and a flat surface evaluated by frictional force...

Area of Science:

• Soft Matter Physics
• Surface Science
• Fluid Dynamics

Background:

• Hydrodynamic interactions are crucial for soft matter applications like emulsions.
• Measuring these forces at the microscale is challenging.
• Atomic Force Microscopy (AFM) offers high-resolution force measurements.

Purpose of the Study:

• To introduce a novel lateral AFM method for quantifying hydrodynamic drag forces.
• To investigate the hydrodynamic interactions between microscopic emulsion droplets and a flat surface.
• To demonstrate the utility of AFM for studying microscale lubrication.

Main Methods:

• Utilized a V-shaped AFM cantilever with an attached tetradecane oil droplet in an aqueous solution.
• Measured lateral hydrodynamic forces by scanning the droplet parallel to a flat glass surface at various velocities.
• Varied droplet proximity to the surface, including conditions with and without applied load.

Main Results:

• Successfully demonstrated the feasibility of the lateral AFM method for measuring hydrodynamic drag.
• Quantified lateral hydrodynamic interactions between the emulsion droplet and the glass surface.
• Showcased the method's ability to probe lubrication phenomena.

Conclusions:

• The developed lateral AFM technique is effective for studying microscale hydrodynamic interactions.
• This method provides insights into the lubricity of soft matter systems.
• The findings have implications for diverse applications, including food science and personal care products.