Issue 43, 2018

Sequential deposition of microdroplets on patterned surfaces

Abstract

We use a combination of experiments and numerical modelling to investigate the influence of physico-chemical-patterned substrates on the spreading of fluid deposited as a partially overlapping sequence of droplets via inkjet printing. Our investigation is motivated by the manufacture of polymeric organic light-emitting-diode displays, where the substrate is textured with a regular array of shallow recessed regions (pixels) that are highly wetting compared to the remainder of the substrate. We examine the roles of topography and wettability patterning separately and in combination. On a substrate with uniform wettability, we find that the presence of bounding side walls enhances the local spreading and facilitates fluid coverage of the entire recessed region, but containment within the pixel is not guaranteed. In contrast, wettability patterning alone leads to robust containment of the fluid within the wetting region, but fluid coverage is reduced in the absence of side walls. Our theoretical calculations use a simplified numerical model of fluid redistribution via purely capillary effects, augmented by a Cox-Voinov spreading law. The neglect of fluid viscosity in this model means that, after an initial period of agreement, the predicted evolution is faster than in the experiments. Nonetheless, the simplified model achieves excellent predictions both for the liquid morphologies and for the conditions required for successful pixel filling on substrates with topographical and wettability variations.

Graphical abstract: Sequential deposition of microdroplets on patterned surfaces

Supplementary files

Article information

Article type
Paper
Submitted
04 Jul 2018
Accepted
03 Sep 2018
First published
04 Sep 2018

Soft Matter, 2018,14, 8709-8716

Sequential deposition of microdroplets on patterned surfaces

P. Kant, A. L. Hazel, M. Dowling, A. B. Thompson and A. Juel, Soft Matter, 2018, 14, 8709 DOI: 10.1039/C8SM01373J

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