Colloidal Deposits via Capillary Bridge Evaporation and Particle Sorting Thereof

Area of Science:

• Materials Science
• Fluid Dynamics
• Colloid Science

Background:

• Evaporation of colloidal suspensions forms particle deposits, controllable by external factors.
• Previous research focused on sessile and pendant droplets, leaving capillary bridges understudied.

Purpose of the Study:

• Investigate evaporation dynamics of colloidal suspensions in capillary bridges between parallel plates.
• Analyze particle deposit formation and explore particle sorting mechanisms.

Main Methods:

• Experimental techniques: side visualization, optical, fluorescence, and scanning electron microscopy.
• Computational and theoretical modeling, including diffusion-limited evaporation models.
• Systematic variation of plate wettability, particle size, and composition.

Main Results:

• Observed multiple ring patterns due to contact line stick-slip motion during evaporation.
• Larger particles exhibited asymmetric deposits, influenced by gravity and hydrodynamic drag.
• Developed a regime map for deposit classification based on particle size and wettability.
• Demonstrated efficient size-based particle sorting using gravity-assisted and geometry-assisted mechanisms.

Conclusions:

• Evaporation dynamics in capillary bridges offer control over colloidal deposit formation.
• Understanding competing forces explains particle deposition patterns.
• The proposed regime maps provide a framework for designing controlled particle deposition and sorting systems.