Multi-Ring Deposition Pattern of Drying Droplets

TL;DR

This paper develops a theoretical model explaining the formation of multi-ring and solid-circle patterns in drying droplets of suspension, highlighting the influence of evaporation dynamics and contact line behavior.

Contribution

It introduces an analytical model predicting the transition from multi-ring to solid-circle patterns during droplet evaporation, aligning qualitatively with experimental observations.

Findings

Analytical expression for pattern transition during evaporation

Evaporation rate influences pattern formation

Droplet size and contact angle affect deposit patterns

Abstract

We propose a theory for the multi-ring pattern of the deposits that are formed when droplets of suspension are dried on a substrate. Assuming a standard model for the stick-slip motion of the contact line, we show that as droplets evaporate, many concentric rings of deposits are formed, but are taken over by a solid-circle pattern in the final stage of drying. An analytical expression is given to indicate when ring-pattern changes to solid-circle pattern during an evaporation process. The results are in qualitative agreement with existing experiments, and the other predictions on how the evaporation rate, droplet radius and receding contact angle affect the pattern are all subject to experimental test.