Mechanics of the low‐flow limit in slot‐die coating with no vacuum

Abstract Slot‐die coating is a premetered, film‐deposition process compatible with a wide range of materials. Of topical interest to precision electronics applications is the deposition of high‐cost nanomaterial dispersions over moderately sized ( >10 cm 2 ) areas with submicron wet film thickness. In this work, a two‐dimensional (2D) model has been developed to understand the limits of the process and to predict the thinnest possible film achievable. Coined the low‐flow limit , this parametric operating boundary presents the minimum uniform, defect‐free film achievable at a given set of liquid properties and die/substrate geometry. We investigate the low‐flow limit with a model that allows menisci to locate anywhere on the die lands, faces, and substrates with prescribed contact angles, thereby minimizing the assumptions on the bead configuration. The model is validated via comparison of its low‐flow limit predictions to published experimental data. Analysis yields insights into the mechanics of coating bead breakdown at the low‐flow limit.