Multi-ring Deposition Pattern of Drying Droplets.

Area of Science:

• Physics of complex fluids
• Materials science
• Surface phenomena

Background:

• Droplet evaporation on substrates is a common phenomenon with applications in printing and materials deposition.
• The resulting deposit patterns are influenced by fluid dynamics and drying kinetics.
• Previous studies have observed various deposit patterns, but a unified theoretical explanation is lacking.

Purpose of the Study:

• To develop a theoretical framework explaining the multi-ring deposit patterns formed during droplet drying.
• To identify the transition mechanism from ring patterns to solid-circle patterns.
• To provide an analytical expression predicting this pattern transition.

Main Methods:

• Modeling droplet evaporation using a standard stick-slip motion model for the contact line.
• Deriving an analytical expression to describe the conditions for pattern transition.
• Comparing theoretical predictions with existing experimental observations.

Main Results:

• The theory successfully explains the formation of multi-ring deposit patterns.
• A transition from ring patterns to a solid-circle pattern is predicted in the final drying stage.
• An analytical expression is derived to determine the onset of this transition based on evaporation parameters.

Conclusions:

• The proposed theory provides a comprehensive explanation for droplet deposit patterns during drying.
• The transition to a solid-circle pattern is an inherent feature of the evaporation process.
• Further experimental validation is suggested to test predictions regarding evaporation rate, droplet radius, and receding contact angle effects.