Stick-slip patterning at low capillary numbers for an evaporating colloidal suspension

Area of Science:

• Colloid science
• Materials science
• Fluid dynamics

Background:

• Evaporation-induced pattern formation in colloidal suspensions is crucial for material fabrication.
• Understanding contact line dynamics, particularly stick-slip motion, is key to controlling these patterns.
• Previous studies have not fully explored pinning forces during deposit growth in low-velocity regimes.

Purpose of the Study:

• To investigate pattern formation in silica colloidal suspensions under controlled contact line movement.
• To analyze the stick-slip regime at very low contact line velocities.
• To quantify the pinning force during contact line pinning on a growing deposit.

Main Methods:

• A specialized capillary rise experiment was designed to observe and measure contact line behavior.
• Systematic measurements of pinning force were conducted.
• Scaling laws were derived by varying contact line velocity, colloid concentration, and evaporation rate.

Main Results:

• The study focused on the stick-slip regime at low contact line velocities.
• Pinning force was measured and found to increase as the contact line pinned to the growing deposit.
• Scaling laws were established for the pinning force based on experimental parameters.

Conclusions:

• The pinning of the contact line is influenced by the interplay between the growing deposit's geometry and gravitational forces.
• The findings provide insights into controlling pattern formation in colloidal systems.
• This research offers a method for measuring pinning forces in evaporating colloidal systems.