The impact of trough geometry on film shape. A theoretical study of droplets containing polymer, for P-OLED display applications
Eales, Adam D
Journal of Colloid and Interface Science
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Eales, A. D., Dartnell, N., Goddard, S., & Routh, A. (2015). The impact of trough geometry on film shape. A theoretical study of droplets containing polymer, for P-OLED display applications. Journal of Colloid and Interface Science, 458 53-61. https://doi.org/10.1016/j.jcis.2015.07.036
For P-OLED display fabrication, it is important to control the final film shape, arising from drying of volatile droplets containing polymer. Due to peripheral pinning and subsequent outward capillary ow, a coffee-ring typically develops. This is in- convenient since a spatially uniform height, above the substrate, is required to ensure uniform current across the device. Typically the droplets are deposited inside a trough- like structure on the substrate. We present a thin-film lubrication model that tracks the drying dynamics through to the final film shape. The governing equations are derived and solved numerically. We investigate the effect of the trough's depth and the slope of the walls. Increasing the depth or the wall's gradient increases coffe-ring formation. This is due to an increase in horizontal velocity, caused by the substrate's shape as well as delayed gelation of the polymer. The latter allows the outward capillary ow to act for a longer time, before the height becomes fixed.
This research has been funded by the Engineering & Physical Sciences Research Council, UK and CASE studentship funding from Cambridge Display Technology Ltd., UK.
External DOI: https://doi.org/10.1016/j.jcis.2015.07.036
This record's URL: https://www.repository.cam.ac.uk/handle/1810/248975
Attribution 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by/2.0/uk/
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