Evaporation of pinned droplets containing polymer – an examination of the important groups controlling final shape
Eales, Adam D
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Eales, A. D., Routh, A. F., Dartnell, N., & Goddard, S. (2015). Evaporation of pinned droplets containing polymer – an examination of the important groups controlling final shape. AIChE Journal, 61 1759-1767. https://doi.org/10.1002/aic.14777
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.
droplet, drying, capillary flow, coffee-ring, P-OLED
This research has been funded by the Engineering & Physical Sciences Research Council, UK and CASE studentship funding from Cambridge Display Technology Ltd., UK. The authors thank Dr Mark Dowling of Cambridge Display Technology Ltd., for help with the experimental setup.
External DOI: https://doi.org/10.1002/aic.14777
Attribution 4.0 UK: England & Wales, Creative Commons Attribution License 4.0 UK
Licence URL: http://creativecommons.org/licenses/by/4.0/uk/