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AIChE Journal, Vol.61, No.5, 1759-1767, 2015
Evaporation of pinned droplets containing polymer - an examination of the important groups controlling final shape
Controlling the final shape resulting from evaporation of pinned droplets containing polymer, is important in the fabrication of P-OLED displays by inkjet printing. Typically, a coffee - ring shape arises, due to the pinning and associated outward capillary flow. For operational reasons, this is undesirable - a flat topography is required. The aim of this work is to understand the important groups governing the shape, to provide a practical guide to ink selection. The theory presented is based on a thin-film lubrication model. The governing equations are solved numerically and continuously track the lateral progression of a liquid/gel front. A large capillary number or large ratio of initial to maximal polymer volume fraction can suppress the coffee-ring. White light interferometry is used to confirm these findings experimentally. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 1759-1767, 2015