Capillary migration of microdisks on curved interfaces

Area of Science:

• Physics
• Colloid Science
• Soft Matter Physics

Background:

• Capillary energy landscapes for particles on fluid interfaces are dictated by wetting conditions.
• Contact line pinning is a common phenomenon for colloidal particles, but its effect on capillary interactions remains underexplored.

Purpose of the Study:

• To investigate the migration behavior of disks with pinned contact lines on curved fluid interfaces.
• To analyze the relationship between capillary energy, interface curvature, and particle migration.

Main Methods:

• Experimental study of microdisk migration on a zero-mean-curvature host interface.
• Analysis of particle trajectories and inferred capillary energy dissipation.
• Theoretical derivation of curvature capillary energy for arbitrary interface curvature.

Main Results:

• Microdisks with pinned contact lines migrate towards regions of steep curvature.
• Capillary energies are linearly dependent on the deviatoric curvature.
• Nanometric deviations from a planar circular contact line drive migration, aligning with experimental observations.

Conclusions:

• Pinned contact lines significantly influence capillary interactions and drive particle migration on curved interfaces.
• The derived curvature capillary energy provides a framework for understanding these interactions.
• Weak surface roughness can induce directed motion in colloidal particles on fluid interfaces.