Ring to Mountain Transition in Deposition Pattern of Drying

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.