  The fabrication of a high-quality POLED (Polymeric Organic Light Emitting
Diode) display requires the deposition of identical, uniform fluid films into a
large number of shallow recessed regions that form a regular array of pixels on
a display backplane. We determine the protocols required to achieve continuous
liquid coverage of the entire pixel area for the case where equally-spaced
fluid droplets are sequentially printed along a straight line within a
stadium-shaped pixel, and explore how these protocols depend on the wetting
properties of the pixel surface. Our investigation uses a combination of
experiments and numerical modelling, based on the assumption of fluid
redistribution via capillary spreading according to a Cox-Voinov law. We show
that the model is able to predict quantitatively the evolution of the liquid
deposited in a pixel and provides a computationally inexpensive design tool to
determine efficient printing strategies that account for uncertainties arising
from imperfect substrate preparation or printhead dysfunction.
