Active control of evaporative solution deposition by means of modulated gas phase convection

In solution processing, functional materials are dissolved or dispersed in a solvent and deposited typically as a thin liquid film on a substrate. After evaporation of the solvent, a dry layer remains. We propose an ‘active’, non-contact technique for evaporative pattern formation that does not require any substrate modification. It is based on an array of nozzles, some of which introduce a dry carrier gas in the air space above the liquid film. By spatially modulating the solvent vapor saturation above the liquid, patterns in the dry layer thickness can be induced in a controlled fashion. In this manuscript we study pattern formation due to a single pixel of such a nozzle array, by means of quantitative experiments and numerical simulations.