A process model for slot coating of narrow stripes

Selective deposition of patterned films, without masks or subtractive postprocessing steps, can potentially be achieved by extending the capabilities of traditional slot coating. Realization of a fully additive-only approach of this nature will elevate the viability of slot coating for numerous emerging technologies such as flexible optoelectronic devices, sensors, and wearables. In this study, we develop a process model for slot coating of variable-width narrow stripes, as a fundamental and representative pattern feature for patterned slot coating. Our process model addresses the sensitivity of stripe output to fluid deposition rate, substrate speed, and coating gap for a given coating material. To explain the observed process behavior, we distinguish between separate configurations of contact line pinning of the liquid bridge at the coating tool surface and show experimentally how these configurations relate to regimes in the process model that must be characterized separately. We also demonstrate how the geometry of the liquid bridge and range of intermediate contact angles along its contact line correspond to observed hysteresis of the coated stripe width.