Ring to Mountain Transition in Deposition Pattern of Drying

TL;DR

This paper presents a theory predicting how the deposit pattern of a drying droplet transitions from a ring to mountain-like shapes, based on fluid flow, contact line motion, and evaporation rate.

Contribution

It introduces an analytical model that describes the continuous transition of deposit patterns in drying droplets, linking contact line mobility and evaporation rate.

Findings

Deposit pattern varies from ring to mountain with changing parameters.

Analytical expression for the peak deposit position is derived.

The model explains the transition mechanism in drying droplet deposits.

Abstract

When a droplet containing a non-volatile component is dried on a substrate, it leaves a ringlike deposit on the substrate. We propose a theory which predicts the deposit distribution based on a model of fluid flow and contact line motion of the droplet. It is shown that the deposition pattern changes continuously from coffee-ring to volcano-like and to mountain-like depending on the mobility of the contact line and the evaporation rate. Analytical expression is given for the peak position of the distribution of deposit left on the substrate.